International Telecommunication Union (ITU) in May 2000 to determine W-CDMA, CDMA2000, TD-SCDMA, as well as the mainstream of the four WiMAX wireless interface standard, 3G technology into the guiding text of the "2000 International Mobile Communications Plan" (referred to as IMT-2000 ). CDMA is Code Division Multiple Access (CDMA) acronym, is the third generation mobile communication technology-based systems. The first generation of mobile communication system using frequency division multiple access (FDMA) analog modulation, the system is the fundamental flaw of the spectrum utilization low, signaling interfere with voice service. Second-generation mobile communications systems using time division multiple access (TDMA) digital modulation, to increase the capacity of the system, and an independent channel signal transmission, so that system performance greatly improved, but the TDMA system capacity is still limited, handoff Performance does not improve. CDMA system, with its simple frequency planning, system capacity, frequency reuse factor of high anti-multipath capability, good communication quality, capacity soft, soft switching characteristics, such as showing great potential for development. The following were some brief 3G standards:
(1) W-CDMA
Also known as WCDMA, called Wideband CDMA, also known as CDMA Direct Spread, which means broadband Code-Division Multiple Access, which is based on the GSM network developed 3G technology standard proposed by the European broadband CDMA technology in Japan The proposed broadband CDMA technology is basically the same as is currently being further integration. Its main supporter of the GSM system is mainly of European manufacturers, Japanese companies are more or less involved, including Europe and the United States of Ericsson, Alcatel, Nokia, Lucent, Nortel, as well as Japan's NTT, Fujitsu, Sharp , And other manufacturers. The system can be set up in the existing GSM network, the system providers can be moved less transition, and the GSM system very popular in Asia for the new technology acceptance is expected to be high. Therefore, W-CDMA has the inherent advantages of the market. The proposed standard GSM (2G)-GPRS-EDGE-WCDMA (3G) evolution strategy. GPRS is General Packet Radio Service (GPRS), referred to as, EDGE is Enhanced Data rate for GSM Evolution (Enhanced Data Rates for GSM Evolution), referred to as the two technologies called 2.5 generation mobile communication technology.
(2) CDMA2000
CDMA2000 is by the narrow-band CDMA (CDMA IS95) technology developed from broadband CDMA technology, also known as CDMA Multi-Carrier, from Qualcomm Inc. led the North American made, Motorola, Lucent, subsequently joined by South Korea's Samsung are involved in the process, South Korea Now become the dominant standard. The system is the digital standard from the narrowband CDMAOne derived from the original structure CDMAOne directly to upgrade to 3G, low-cost construction. However, the use of CDMA, only Japan, South Korea and North America, CDMA2000 is why supporters of more than W-CDMA. However, the CDMA2000 technology research and development is currently the fastest progress in standards, and many have been the first to launch 3G mobile phone. The proposed standards from the CDMA IS95 (2G)-CDMA20001x-CDMA20003x (3G) evolution strategy. CDMA20001x called 2.5 generation mobile communication technology. CDMA20003x and CDMA20001x the main difference is that the application of multi-carrier technology, so that through the use of three carrier to increase bandwidth. At present, China Unicom is using the program to transition to 3G and has built a network of CDMA IS95.
(3) TD-SCDMA
Full-called Time Division - Synchronous CDMA (Time Division Synchronous CDMA), by the standards of the Chinese mainland's development of its own 3G standard, June 29, 1999, China's former Ministry of Posts and Telecommunications Academy of Telecommunications Technology (Datang Telecom) made to the ITU. The intelligent wireless standard, synchronous CDMA radio and software, and so today the world's leading technology into one, in the spectrum utilization, and support for business flexibility, frequency and flexibility in areas such as the cost of the unique advantages. In addition, because of the huge domestic market, which is subject to major telecommunications equipment manufacturers attention, more than half of the global equipment manufacturers have announced to support TD-SCDMA standard. The proposed standard without going through the middle of the 2.5-generation link directly to the transition to 3G, is applicable to the GSM system upgrade to 3G.
(4) WiMAX
WiMAX is the full name of the Worldwide Interoperability for Microwave Access (Worldwide Interoperability for Microwave Access), also known as the 802.16 wireless MAN, is also a corporate and home users to provide "last mile" broadband wireless connection program. This technology and the need to avoid authority or authorized by the combination of microwave equipment, due to lower-cost, wireless broadband market will expand and improve the enterprises and service providers awareness. October 19, 2007, the International Telecommunication Union in Geneva at the plenary meeting of wireless communications, after most countries vote, WiMAX was approved to become official following the WCDMA, CDMA2000 and TD-SCDMA after the fourth of global 3G standards.
Monday, October 13, 2008
GPRS and GPS
They do not belong to one area of technology, but we can not in the same breath.
According to reports, GPS for "global positioning system", a location technology to recognize objects of latitude and longitude position, at least 10 years there will not be more advanced than the GPS positioning technology. The GPRS is intended to "General Packet Radio Service data" is just a data transfer method used to transfer data group, as mobile phones to send text messages, do not have any position or function of anti-theft robbery. GPRS is a GPS component, for the application of GPS technology played a data transmission. If the GPS leader, "St. SEG car", there are several ways to use GPRS data transmission.
According to reports, GPS for "global positioning system", a location technology to recognize objects of latitude and longitude position, at least 10 years there will not be more advanced than the GPS positioning technology. The GPRS is intended to "General Packet Radio Service data" is just a data transfer method used to transfer data group, as mobile phones to send text messages, do not have any position or function of anti-theft robbery. GPRS is a GPS component, for the application of GPS technology played a data transmission. If the GPS leader, "St. SEG car", there are several ways to use GPRS data transmission.
GPRS technology
1.GPRS technology embodied
General Packet Radio Service GPRS, GSM-based system is a wireless packet switching technology, to provide end-to-end, wide-area wireless IP connection. Tongsudejiang, GPRS is a high-speed data-processing technology, methods of "division" in the form of transmitting information to the hands of the user. Although GPRS is available as a GSM network to the 3G mobile communications technology evolution of the transition, but in many ways, has a significant advantage. At present, Hong Kong's status as the first testing ground for GPRS areas, have achieved good results.
Due to the use of a "group" of technology, Internet users can be disconnected from the suffering of the (situation about the use of just a software download NetAnts almost). In addition, the use of GPRS and WAP access to the Internet and in different ways, such as WAP access on the Internet at home, the first "dial-up connection" and then the Internet can not use the telephone line, but on more favorable GPRS, download information and can call At the same time. Technically, the transmission of voice (that call) to continue to use GSM, and data can be transmitted using GPRS, this is the case, put mobile phone applications to a higher level. GPRS technology development and also the "economy", because only the existing GSM network to develop. GPRS uses the wide range of issues, including the adoption of mobile phones to send and receive e-mail, browse the Internet, and so on.
Internet phones are now the slogan is "always online", "IP in hand", using GPRS, the realization of the data packet to send and receive, at the same time this means that the user is always online and by billing traffic, to quickly lower the costs of the services. The continued state of dystocia in China Mobile / Unicom WAP tariff policy, if the CSD (circuit-switched data, that is usually said that the dial-up data, WAP European and Asian business methods used by the bearer) carrying changed to achieve the GPRS, it means that Dozens of people from a common commitment to one of the original cost.
And GPRS the greatest advantage: its data transfer speed is not WAP can be compared. The current GSM mobile communications network for the transmission speed of 9.6K bytes per second, GPRS mobile phones launched in the beginning of this year have reached a speed of 56Kbps, up to now is to achieve a 115Kbps (this is the speed of common ideals 56Kmodem twice the rate) . Therefore, we cherish you in the hands of Nokia7110 and MotorolaL2000, I believe that the introduction of GPRS handsets, they have to give way.
2. Packet (Packet) technology
The so-called packet (Packet) is the Date package into a number of separate packets, and then these packets to send out one by one, a bit similar in form to send parcels, the advantages of using packet-switched only when there is a need to send information when Will take up bandwidth, but also to transfer the amount of data pricing, which the user is a more reasonable way of accounting, because the Internet such as data transmission bandwidth is most of the time between the home. In addition, GSM phase 2, the standard, GPRS offers four different coding methods, the encoding also provide different protection error (Error Protection) capability. The use of four different encoding every time slot available for transfer rate of CS-1 (9.05K), CS-2 (13.4K), CS-3 (15.6K) and CS-4 (21.4K), which CS-1 to protect the most rigorous, CS-4, it is absolutely not be any protection. At the same time, each user can use a maximum of eight hours slot, so-called GPRS for a maximum transfer rate of 171.2K.
3.GPRS network structure
GPRS network is based on the existing GSM network to achieve. In the existing GSM networks need to increase the number of nodes, such as GGSN (Gateway GPRSSupporting Node, Gateway GPRS support node) and SGSN (Serving GSN, to support the GPRS service node).
GPRS network reference model as shown in Figure 1. GSN is the GPRS network, the most important nodes of the network. GSN with a mobile routing management functions, which can connect various types of data networks and can be connected to the GPRS register. GSN to be completed and a variety of mobile data network between the data and format conversion. GSN can be a similar independent of routers and prepared, in the GSM and can also be integrated with the MSC.
GSN There are two types: one for the SGSN (Serving GSN, services GSN), the other for the GGSN (GatewayGSN, Gateway GSN), SGSN main role is to record the mobile station from its current location information and mobile station and GGSN Between the completion of the mobile division to send and receive data. GGSN is the main gateway from the role it can be a wide range of data and network connections such as ISDN, PSPDN and LAN, and so on. Some of the literature, the GGSN called GPRS router. GGSN can GSM network in the GPRS packet data protocol conversion package that will allow these groups to send packets to the remote TCP / IP or X.25 network.
In addition, some manufacturers raised GR (GSMRegister, GPRS data) concept. GR similar to the GSM in the HLR, is a GPRS business database. It can stand on its own, and can co-exist HLR by the server or the realization of program-controlled switches. GR in the name of the ETSI's proposal does not specifically mentioned.
GPRS network also introduced a new network interface of the following:
Gn, GSN backbone interface for a variety of between GSN
Gb, BSS and the interface between the sGsN.
Gr, SGSN and the interface between the HLR.
Gp, different GSM networks (different PLMN) interface between.
Gs, SGSN and the interface between the MSC.
4.GPRS agreement model
Um is the interface of the GSM air interface. Um interface communication protocol layer 5, bottom-up followed by the physical layer, MAC Mdium AccessControl) layer, LLC (Logical Link Control) layer, SNDC (Subnetwork DependantConvergence) layer and network layer.
Um interface of the physical layer for the radio frequency interface, and the physical link layer is responsible for providing a variety of air interface logical channel. GSM air interface to the carrier frequency bandwidth 20OkHz, a carrier frequency is divided into 8 physical channels.
8 If you have physical distribution channel for the transmission of GPRS data, the raw data rate of up to 20Okb / s. Forward Error Correction Code to consider the costs, the final data rate of up to 164kb / s or so.
MAC for media access control layer. MAC's main role is to define the distribution of air interface and the GPRS logical channel, so that these channels will be different mobile sharing. GPRS logical channel of a total of 3 categories, namely, the Public Channel, channel and business groups GPRS radio channel. Public Channel used to transmit data communications control signaling, is subdivided into specific responses, such as paging and channel. Business groups to channel packet data transmission. Radio channel is used to the mobile network to send information.
LLC Logical Link Control layer to layer. It is a high-speed data link based on the order of the HDLC protocol wireless link. LLC layer is responsible for the high-level SNDC layer SNDC data unit formed LLC address field frame in order to generate full-frame LLC. In addition, LLC can be a point-to-multipoint addressing the frame and the re-issued control.
LLR in the BSS layer is a logical link layer transmission. This layer is responsible for MS and SGSN transfer between the frame LLC. LLR layer SNDC for the data unit is transparent, that is not responsible for SNDC data.
SNDC known as the combination dependence on sub-layer. Its main role is to complete the transfer of data packet, packing, determine the TCP / IP address and encryption methods. SNDC in the layer, mobile and data transmission between the SGSN has been divided into one or more packets SNDC unit. SNDC packet generation unit was placed intra LLC.
Network layer protocol of the current stage of Phase 1 is provided by the TCP / IP protocol and L25. TCP / IP and X.25 protocol to the traditional GSM network equipment (such as equipment such as the NSS and BSS) is transparent.
5.GPRS routing management
GPRS is the management of the routing GPRS networks and addressing how to set up a data transmission route. GPRS routing management in the following 3 areas: mobile station to send data to establish the route; mobile station set up to receive data routing; and mobile roaming at the time of the establishment of routing data.
In the first case, in Figure 3 shown in a path. When the mobile station have had a PDU (packet data unit), the PDU after SNDC layer processing, called SNDC data unit. LLC layer and then, after dealing with LLC for CHENG through the air interface to the GSM mobile network in Taiwan's SGSN. SGSN the data sent to the GGSN. GGSN to receive the news of solutions for dealing with equipment, can be converted into a public data transmission network in the format (such as PSPDN the PDU), a public data network to the end user. In order to improve the efficiency of the transmission, data transmission and to ensure the safety of air interface can be done on data compression and encryption.
In the second case, a public data network users send data to mobile station. First of all, the data network through the establishment of a standard agreement between the GGSN and data network routing. Data issued by the network user data unit (for example, PSPDN in the PDU), through the establishment of good data routing unit PDU to GGSN. GGSN and then to the PDU mobile station where the SGSN on GSN into the PDU package SNDC data unit, another layer to deal with LLC to LLC unit frame and eventually through the air interface to the mobile station.
The third is a data network to transmit data to a user is roaming of mobile users. The data must go through attribution to the GGSN, and then sent to the mobile user A. In the air by the mouth of the channel constitutes a GPRS air interface channel as follows:
PDTCH (Pachet Data Traffic Channe1), packet data channel. This channel used to send the air interface GPRS packet data.
PPCH (Packet Paging Channe1), group paging channel for paging PPCH called GPRS users.
PRACH (Packet Randem Access Channel), grouping random access channel. GPRS users PRACH to the base station to issue a request channel.
PAGCH (Packet Access Grant Channel), Packet Access response channel. PAGCH is a response channel, the response to PRACH.
PACCH (Packet Asscrchted ControlChannel), with the sub-Channel routes. This channel used to send the realization of GPRS data services signaling.
6. GPRS technology services
GPRS packet data billing functions, that is, according to billing data.
7. GPRS and IP
The introduction of GPRS technology, telecommunications networks and computer networks, organically linked to North Korea in the future all-IP network platform for development.
GPRS can be seen from the structure, the base station and the connection between the SGSN prepared through the general frame relay connection, SGSN and GGSN equipment between the IP network.
GGSN may be replaced by an NAT (network address translation) routers to assume the function of internal and external IP address of the IP network address translation, MS may be accessed within the GPRS network can also be APN (external network access by name) to visit the external PDN / Internet network.
Logo in the GPRS devices such as mobile phones MS logo in addition to the GSM used in the IMSI, MSISDN number, and so on, but also need the distribution of IP addresses. Network element equipment SGSN, GGSN logo of the existing SS7 address, and the IP address of the GGSN data, GSN (SGSN or GGSN) communications between the use of IP addresses, and GSN with the MSC, HLR, and other entities use of communication 7 Signaling its address. GPRS in the system, there are two important records database information. First, the user mobility management context for the management of the mobile user location information, and the other is the user context of the PDP (Packet Data context of the agreement) for the management of MS from the phone to Gateway GGSN and the ISP (Internet Service Provider ) Between the data routing information. When MS access GPRS network internal or external PDN / Internet network, MS to activate PDP fat SGSN context of a request message, MS may choose to contract with the operator of fixed service GGSN. According to the rules of APN or choose from SGSN choice GGSN, SGSN made GGSN to the establishment of information PDP context request. GGSN allocated an IP address of the MS (static or dynamic, public or private), set up in the context of the PDP, the need for the user's identity, the need for quality of service for authentication and verification in the successful establishment and activation after the PDP context, MS , SGSN and GGSN are stored PDP context of the user's information. With the user's location information and data routing information, MS will be able to access the network resources. Second-generation GPRS and a half of the products available in the development and deployment of GPRS business encountered some new concepts.
GPRS application
1.GPRS of WAP application
WAP and GPRS is a combination of current orders, "Internet phone" to a new level of the best implementation of the program: GPRS is a powerful underlying transport, WAP is a high-level applications, if the WAP as a speeding vehicle, then GPRS is wide open for high-speed Road, you any information in the wireless world of surf at random.
2. Equipment
In addition to the GPRS cellular phone can be a variety of devices other than the reality, including the laptop computer PCMCIA modem, personal digital assistants and the extension of the hand-held computer. At present, the popular E-mail portable device BlackBerry (BlackBerry) manufacturer Research in Motion (RIM) in a Microcell Telecommunications known as the GSM providers to study how the other for GPRS wireless system to send messages.
3.GPRS business applications
Since the first text messaging, wireless data applications has gone through a leap of growth, just look at the well-known European and American manufacturers publicized General Packet Radio Service (GPRS) of thrust seems to be able to feel the next generation of mobile Data applications will be the advent of the era. 99 will be the end or early in 2000 to open the General Packet Radio Service GPRS, into a third-generation personal multimedia services an important milestone will enable mobile communications and data networks together so that the IP business to the introduction of a broad mobile market . Although the use of mobile data is a relatively small, but in some markets, the different user groups are being developed rapidly, its main driving force in the area of mobile data services used in the commercial market. Whether Ericsson, Nokia or Alcatel, almost all of the publicity GPRS manufacturers are business users of the fast-growing market to persuade the operator.
GSM system for mobile data communications division (that is, GPRS) is the basic packet radio service, using packet switching the way, the data rate of up to 164kb /, it can be to provide GSM mobile environment, high-speed data business, but also Transceiver to provide Emai1, Internet access features such cases.
4.GPRS function of the corresponding business applications
GPRS is a new GSM data services, which can give mobile users with wireless data packet access Services Unit. GPRS is a remote and mobile users in the data network (such as support for the TCP / IP, X.25 network, and so on) to provide a connection between so as to provide users with high-speed mobile wireless IP and wireless business X.25.
Using GPRS packet switching technology, which allows multiple users to share some of the fixed channel resources. If the air interface on the TDMA frame of 8 slots are used to transmit data, the data rate of up to 164kb/8.GSM air interface channel resources can be occupied by voice, GPRS data services can be occupied. Of course, in the channel adequate conditions, can channel some of the definition of GPRS dedicated channel.
To achieve the GPRS network, the need for the traditional GSM network, the introduction of a new network interface and communication protocols. At present, the introduction of GPRS network GSN (GPRS SurportingNode) node. Taiwan Mobile will be GPRS mobile station or GPRS / GSM dual-mode mobile station.
WAP and GPRS is a combination of current orders, "Internet phone" to a new level of the best implementation of the program: GPRS is a powerful underlying transport, WAP is a high-level applications, if the WAP as a speeding vehicle, then GPRS is wide open for high-speed Road, you any information in the wireless world of surf at random.
2. Equipment
In addition to the GPRS cellular phone can be a variety of devices other than the reality, including the laptop computer PCMCIA modem, personal digital assistants and the extension of the hand-held computer. At present, the popular E-mail portable device BlackBerry (BlackBerry) manufacturer Research in Motion (RIM) in a Microcell Telecommunications known as the GSM providers to study how the other for GPRS wireless system to send messages.
3.GPRS business applications
Since the first text messaging, wireless data applications has gone through a leap of growth, just look at the well-known European and American manufacturers publicized General Packet Radio Service (GPRS) of thrust seems to be able to feel the next generation of mobile Data applications will be the advent of the era. 99 will be the end or early in 2000 to open the General Packet Radio Service GPRS, into a third-generation personal multimedia services an important milestone will enable mobile communications and data networks together so that the IP business to the introduction of a broad mobile market . Although the use of mobile data is a relatively small, but in some markets, the different user groups are being developed rapidly, its main driving force in the area of mobile data services used in the commercial market. Whether Ericsson, Nokia or Alcatel, almost all of the publicity GPRS manufacturers are business users of the fast-growing market to persuade the operator.
GSM system for mobile data communications division (that is, GPRS) is the basic packet radio service, using packet switching the way, the data rate of up to 164kb /, it can be to provide GSM mobile environment, high-speed data business, but also Transceiver to provide Emai1, Internet access features such cases.
4.GPRS function of the corresponding business applications
GPRS is a new GSM data services, which can give mobile users with wireless data packet access Services Unit. GPRS is a remote and mobile users in the data network (such as support for the TCP / IP, X.25 network, and so on) to provide a connection between so as to provide users with high-speed mobile wireless IP and wireless business X.25.
Using GPRS packet switching technology, which allows multiple users to share some of the fixed channel resources. If the air interface on the TDMA frame of 8 slots are used to transmit data, the data rate of up to 164kb/8.GSM air interface channel resources can be occupied by voice, GPRS data services can be occupied. Of course, in the channel adequate conditions, can channel some of the definition of GPRS dedicated channel.
To achieve the GPRS network, the need for the traditional GSM network, the introduction of a new network interface and communication protocols. At present, the introduction of GPRS network GSN (GPRS SurportingNode) node. Taiwan Mobile will be GPRS mobile station or GPRS / GSM dual-mode mobile station.
The development of GPRS
According to the European ETSI's first GSM Phase 2 +, GPRS is divided into two stages of development (that is, Phase 1 and Phase2). GPRS stage of the Phase l will be able to function and support the following:
1.TCP/IP business and X.25
2.'s New GPRS air interface encryption technology
Additional business 3.GPRS
4. Enhanced SMS (E-SMs)
GPRS packet data billing functions, that is, based on the amount of data taken by the above-mentioned functions of billing operations of the most significant is the TCP / IP and X.25 functions. GSM network via TCP / IP and X.25 to provide users with e-mail, WWW browser, a dedicated data, LAN access and other services. GPRS Phase 2 stage of the norms are still being worked out, it will be able to provide more new features and new business.
1.TCP/IP business and X.25
2.'s New GPRS air interface encryption technology
Additional business 3.GPRS
4. Enhanced SMS (E-SMs)
GPRS packet data billing functions, that is, based on the amount of data taken by the above-mentioned functions of billing operations of the most significant is the TCP / IP and X.25 functions. GSM network via TCP / IP and X.25 to provide users with e-mail, WWW browser, a dedicated data, LAN access and other services. GPRS Phase 2 stage of the norms are still being worked out, it will be able to provide more new features and new business.
GPRS features
1. Application on the characteristics of
At present, the Internet using a mobile phone is also a bit less than satisfactory. As a result, a comprehensive solution GPRS so it came into being, this new technology can make you at any time, any place can be quickly and easily connect at the same time very reasonable cost. In short: speed up, and rich in content, applications increased, while the costs are more reasonable.
(1) high-speed data transmission
10 times the speed of GSM, but also fulfill the needs of your ideals, but also to stability in the transmission of high-capacity, high-quality audio and video files, is generally not great progress.
(2) always-on
Since the establishment of a new connection without almost any time (that is, no need for each visit to the establishment of the data call connection), so any time you can keep in touch and network, for example, in the absence of support for GPRS, is when you surf the net, and At this point there is just phone access, most of the time you have to get disconnected after the call, the call after the re-dial-up. For most people, this really is very irritating. And with GPRS, you can easily resolve this conflict.
(3) only by the flow of data billing
That is, based on the amount of data you transfer (such as: downloading information) to billing, rather than time online billing is to say, not as long as data transmission, even if you have been "online", and need not pay. To be a "call" for instance, the use of GSM WAP mobile Internet access, like telephone billing began to get through; use GPRS WAP Internet access will be much more reasonable, just as telephone access charges is not only dialogue When calculating the cost. In short, it truly reflects the use of low pay.
2. Technical characteristics
Data sent to realize and accept the subsector, according to the billing flow; 56 ~ 115Kbps transmission speed.
Due to the use of a "group" of technology, Internet users can be disconnected from the suffering of the (situation about the use of just a software download NetAnts almost). In addition, the use of GPRS and WAP access to the Internet and in different ways, such as WAP access on the Internet at home, the first "dial-up connection" and then the Internet can not use the telephone line, but on more favorable GPRS, download information and can call At the same time. Technically, the transmission of voice (that call) to continue to use GSM, and data can be transmitted using GPRS, this is the case, put mobile phone applications to a higher level. GPRS technology development and also the "economy", because only the existing GSM network to develop. GPRS uses the wide range of issues, including the adoption of mobile phones to send and receive e-mail, browse the Internet, and so on.
Internet phones are now the slogan is "always online", "IP in hand", using GPRS, the realization of the data packet to send and receive, at the same time this means that the user is always online and by billing traffic, to quickly lower the costs of the services. The continued state of dystocia in China Mobile / Unicom WAP tariff policy, if the CSD (circuit-switched data, that is usually said that the dial-up data, WAP European and Asian business methods used by the bearer) carrying changed to achieve the GPRS, it means that Dozens of people from a common commitment to one of the original cost.
GPRS greatest advantage is its data transfer speed is not WAP can be compared. The current GSM mobile communications network for the transmission speed of 9.6kbps, GPRS mobile phones launched in the beginning of this year have reached a speed of 56Kbps, up to now is to achieve a 115Kbps (this is the speed of common ideals 56Kmodem twice the rate).
GPRS is packet-switched data transmission manner, is due to packet switching, so the utilization of network resources than circuit-switched has been greatly improved, but at the same time GPRS voice and data transmission and billing Can be produced in accordance with the traffic statistics. The existing WAP is the bearer of the circuit-switched (CSD) way, way circuit-switched voice and data can not be carried out at the same time, in accordance with the charging system is also a long time to charge.
In fact its own WAP and GPRS are not comparable in nature, the existing WAP content in the above GPRS can browse and application of GPRS is only available means of CSD's WAP faster, more convenient and more reasonable charges, WAP services on the network also due to technological advances and greater promotion and improvement.
In the long run, WAP are using CSD (circuit-switched data), GSM data services, after the WAP can also use GPRS to the new GSM network as a way of carrying.
Therefore, GPRS will not replace the WAP, to cite an example of the image: GPRS and CSD is the way the GSM data services are the road, WAP is a road car, WAP is now running in lane two, GPRS enhanced data transfer speed , Is the 8-lane, it can be said GPRS enhanced WAP services, available on WAP content can browse through GPRS and applications.
GPRS application, but also later with Bluetooth (Bluetooth). At that time, plus a digital camera bluetooth, can be immediately adopted by the phone to send photos to distant places, but a quarter of an hour's time, let cool, this time we will be away from far away.
3.GPRS compared with the GSM show the characteristics of
Compared to the GSM terms of the speed of 9.6kbps visit, GPRS speeds have 171.2kbps visit; in the establishment of connection time, GSM needed 10-30 seconds, and GPRS only a very short period of time can be related to the visit request; for Terms of cost, GSM is connected by the time of billing, and the only GPRS data traffic according to billing; GPRS network resources utilization and relatively much higher than the GSM.
4.GPRS correspond to the characteristics of the scope of services
1. M-Commerce
2. Mobile Information Service
3. Mobile Internet
4. Multimedia services
The technical 5.GPRS advantage
(1) relatively low-cost connectivity
High resource utilization in the GSM network, GPRS introduction of the first packet-switched transmission mode, making use of the original model of the circuit-switched GSM data transmission means there has been a fundamental change in wireless scarce resources under the circumstances it is particularly important. According to circuit-switched mode, to connect the entire period, regardless of whether users will send data occupies its own wireless channel. In conversation, many applications are often a lot of free time, as Internet browsing, send and receive E-mail and so on. The packet switching mode, the user only send or receive data only during the occupation of resources, which means that multiple users can efficiently share the same wireless channel, resulting in improved resource utilization. GPRS user billing to the amount of data communications as the main basis for the concept of "how much, how much to pay" principle. In fact, GPRS users to connect up to a few hours time, but pay relatively low-cost connections.
(2) a high transfer rate
GPRS will provide up to 115kbit / s transfer rate (the highest value for 171.2kbit / s, not including FEC). This means that in a few years, portable computers, GPRS, and ISDN users the same user to quickly browse the Internet, as well as some of the transmission rate-sensitive mobile multimedia applications possible.
(3) access packet-switched access time is short time for less than 1GPRS is a new GSM data services, which can give mobile users with wireless data packet access Services Unit. GPRS is a remote and mobile users in the data network (such as support for the TCP / IP, X.25 network, and so on) to provide a connection between so as to provide users with high-speed mobile wireless IP and wireless business X.25.
Using GPRS packet switching technology, which allows multiple users to share some of the fixed channel resources. If the air interface on the TDMA frame of 8 slots are used to transmit data, the data rate of up to 164kb/8.GSM air interface channel resources can be occupied by voice, GPRS data services can be occupied. Of course, in the channel adequate conditions, the number of channels can be defined as GPRS dedicated channel. To achieve the GPRS network, the need for the traditional GSM network, the introduction of a new network interface and communication protocols. At present, the introduction of GPRS network GSN (GPRS Surporting Node) node. Taiwan Mobile will be GPRS mobile station or GPRS / GSM dual-mode mobile station.
At present, the Internet using a mobile phone is also a bit less than satisfactory. As a result, a comprehensive solution GPRS so it came into being, this new technology can make you at any time, any place can be quickly and easily connect at the same time very reasonable cost. In short: speed up, and rich in content, applications increased, while the costs are more reasonable.
(1) high-speed data transmission
10 times the speed of GSM, but also fulfill the needs of your ideals, but also to stability in the transmission of high-capacity, high-quality audio and video files, is generally not great progress.
(2) always-on
Since the establishment of a new connection without almost any time (that is, no need for each visit to the establishment of the data call connection), so any time you can keep in touch and network, for example, in the absence of support for GPRS, is when you surf the net, and At this point there is just phone access, most of the time you have to get disconnected after the call, the call after the re-dial-up. For most people, this really is very irritating. And with GPRS, you can easily resolve this conflict.
(3) only by the flow of data billing
That is, based on the amount of data you transfer (such as: downloading information) to billing, rather than time online billing is to say, not as long as data transmission, even if you have been "online", and need not pay. To be a "call" for instance, the use of GSM WAP mobile Internet access, like telephone billing began to get through; use GPRS WAP Internet access will be much more reasonable, just as telephone access charges is not only dialogue When calculating the cost. In short, it truly reflects the use of low pay.
2. Technical characteristics
Data sent to realize and accept the subsector, according to the billing flow; 56 ~ 115Kbps transmission speed.
Due to the use of a "group" of technology, Internet users can be disconnected from the suffering of the (situation about the use of just a software download NetAnts almost). In addition, the use of GPRS and WAP access to the Internet and in different ways, such as WAP access on the Internet at home, the first "dial-up connection" and then the Internet can not use the telephone line, but on more favorable GPRS, download information and can call At the same time. Technically, the transmission of voice (that call) to continue to use GSM, and data can be transmitted using GPRS, this is the case, put mobile phone applications to a higher level. GPRS technology development and also the "economy", because only the existing GSM network to develop. GPRS uses the wide range of issues, including the adoption of mobile phones to send and receive e-mail, browse the Internet, and so on.
Internet phones are now the slogan is "always online", "IP in hand", using GPRS, the realization of the data packet to send and receive, at the same time this means that the user is always online and by billing traffic, to quickly lower the costs of the services. The continued state of dystocia in China Mobile / Unicom WAP tariff policy, if the CSD (circuit-switched data, that is usually said that the dial-up data, WAP European and Asian business methods used by the bearer) carrying changed to achieve the GPRS, it means that Dozens of people from a common commitment to one of the original cost.
GPRS greatest advantage is its data transfer speed is not WAP can be compared. The current GSM mobile communications network for the transmission speed of 9.6kbps, GPRS mobile phones launched in the beginning of this year have reached a speed of 56Kbps, up to now is to achieve a 115Kbps (this is the speed of common ideals 56Kmodem twice the rate).
GPRS is packet-switched data transmission manner, is due to packet switching, so the utilization of network resources than circuit-switched has been greatly improved, but at the same time GPRS voice and data transmission and billing Can be produced in accordance with the traffic statistics. The existing WAP is the bearer of the circuit-switched (CSD) way, way circuit-switched voice and data can not be carried out at the same time, in accordance with the charging system is also a long time to charge.
In fact its own WAP and GPRS are not comparable in nature, the existing WAP content in the above GPRS can browse and application of GPRS is only available means of CSD's WAP faster, more convenient and more reasonable charges, WAP services on the network also due to technological advances and greater promotion and improvement.
In the long run, WAP are using CSD (circuit-switched data), GSM data services, after the WAP can also use GPRS to the new GSM network as a way of carrying.
Therefore, GPRS will not replace the WAP, to cite an example of the image: GPRS and CSD is the way the GSM data services are the road, WAP is a road car, WAP is now running in lane two, GPRS enhanced data transfer speed , Is the 8-lane, it can be said GPRS enhanced WAP services, available on WAP content can browse through GPRS and applications.
GPRS application, but also later with Bluetooth (Bluetooth). At that time, plus a digital camera bluetooth, can be immediately adopted by the phone to send photos to distant places, but a quarter of an hour's time, let cool, this time we will be away from far away.
3.GPRS compared with the GSM show the characteristics of
Compared to the GSM terms of the speed of 9.6kbps visit, GPRS speeds have 171.2kbps visit; in the establishment of connection time, GSM needed 10-30 seconds, and GPRS only a very short period of time can be related to the visit request; for Terms of cost, GSM is connected by the time of billing, and the only GPRS data traffic according to billing; GPRS network resources utilization and relatively much higher than the GSM.
4.GPRS correspond to the characteristics of the scope of services
1. M-Commerce
2. Mobile Information Service
3. Mobile Internet
4. Multimedia services
The technical 5.GPRS advantage
(1) relatively low-cost connectivity
High resource utilization in the GSM network, GPRS introduction of the first packet-switched transmission mode, making use of the original model of the circuit-switched GSM data transmission means there has been a fundamental change in wireless scarce resources under the circumstances it is particularly important. According to circuit-switched mode, to connect the entire period, regardless of whether users will send data occupies its own wireless channel. In conversation, many applications are often a lot of free time, as Internet browsing, send and receive E-mail and so on. The packet switching mode, the user only send or receive data only during the occupation of resources, which means that multiple users can efficiently share the same wireless channel, resulting in improved resource utilization. GPRS user billing to the amount of data communications as the main basis for the concept of "how much, how much to pay" principle. In fact, GPRS users to connect up to a few hours time, but pay relatively low-cost connections.
(2) a high transfer rate
GPRS will provide up to 115kbit / s transfer rate (the highest value for 171.2kbit / s, not including FEC). This means that in a few years, portable computers, GPRS, and ISDN users the same user to quickly browse the Internet, as well as some of the transmission rate-sensitive mobile multimedia applications possible.
(3) access packet-switched access time is short time for less than 1GPRS is a new GSM data services, which can give mobile users with wireless data packet access Services Unit. GPRS is a remote and mobile users in the data network (such as support for the TCP / IP, X.25 network, and so on) to provide a connection between so as to provide users with high-speed mobile wireless IP and wireless business X.25.
Using GPRS packet switching technology, which allows multiple users to share some of the fixed channel resources. If the air interface on the TDMA frame of 8 slots are used to transmit data, the data rate of up to 164kb/8.GSM air interface channel resources can be occupied by voice, GPRS data services can be occupied. Of course, in the channel adequate conditions, the number of channels can be defined as GPRS dedicated channel. To achieve the GPRS network, the need for the traditional GSM network, the introduction of a new network interface and communication protocols. At present, the introduction of GPRS network GSN (GPRS Surporting Node) node. Taiwan Mobile will be GPRS mobile station or GPRS / GSM dual-mode mobile station.
GPRS Overview
GPRS is General Packet Radio Service (General Packet Radio Service) abbreviation, it can only be broken through the GSM network to provide circuit-switched way of thinking, only by increasing the functionality of the existing entities and the base part of the system to achieve reform Packet switching, the transformation of inputs is not relatively large, but the user data rate is quite impressive. GPRS (General Packet Radio Service) is a global system of mobile (GSM)-based data transfer technology, is an extension of GSM. GPRS and in the past in a row in the channel of transmission in different ways, based on packet (Packet)-transmission to, so users have to pay the costs of its transmission is calculated on the basis of the information, not to use their channels as a whole, in theory, cheaper.
GPRS transmission rate can be raised to 56 or even 114Kbps. Moreover, no longer needed because the existing wireless applications intermediaries need converter, the connection will be more convenient and easier to transport. However, users can access on-line, participate in the dissemination of interactive video conferencing and video on the same network (VRN) user, even without the need for dial-up, and continued with the network connection.
GPRS transmission rate can be raised to 56 or even 114Kbps. Moreover, no longer needed because the existing wireless applications intermediaries need converter, the connection will be more convenient and easier to transport. However, users can access on-line, participate in the dissemination of interactive video conferencing and video on the same network (VRN) user, even without the need for dial-up, and continued with the network connection.
Saturday, October 11, 2008
U.S. digital mobile communication system
In fact, the United States is the so-called PCS digital mobile communication system services collectively. In particular, PCS is a digital mobile phone includes, cordless phone (Codeless Phone) and fixed wireless connection (FWA), and so on a broader range of communications services collectively. While in Japan, including the PHS, mobile phone known as the "cell phone", but PCS is a broader term meaning.
PCS is a sprint of the United States to launch a network service, which is the predecessor of the PTT (PushToTalk) is a call for one-to-many network of services, is only the beginning of the most TALK function, and later with value-added services such as voicemail, then changed its name Known as PTC (PushToCommunication) up to now the service is already very mature, full name called Sprint PCS vision PCS is full name of the push to communication service
PCS is a sprint of the United States to launch a network service, which is the predecessor of the PTT (PushToTalk) is a call for one-to-many network of services, is only the beginning of the most TALK function, and later with value-added services such as voicemail, then changed its name Known as PTC (PushToCommunication) up to now the service is already very mature, full name called Sprint PCS vision PCS is full name of the push to communication service
PCS
PCS is an acronym for Personal Communications Service, which means "personal communication services." This is the Federal Communications Commission (FCC) to use a term, the correction in the United States to deploy a set of digital cellular technology. PCS, including CDMA (also known as IS-95), GSM and for the North American TDMA (also called IS-136). The PCS frequency of 1900MHz
Friday, October 10, 2008
GSM and CDMA mobile phone radiation
As we all know, due to CDMA (IS-95) system used to control power reverse the rapid, soft switches, voice-activated technology, as well as the IS-95 specification of the largest mobile phone transmission power limitations, so that the CDMA mobile phone communications in the course of radiation power is Small and enjoy the "green phone" in the world. However, there are a number of recent reports on the "green phone" raised questions that the GSM and CDMA mobile phone radiation rather, their basic view is that only one-eighth of the GSM mobile phone radiation have the time, the GSM and CDMA mobile phone SAR value (the human body Absorbing quality of the units of RF power) generally quite.
What GSM and CDMA mobile phone radiation power who is who in small or big difference, in order to arrive at an objective comparison of the actual results, by a well-known international authority of the CDMA technology and a well-known domestic GSM network optimization company engineers and technicians in 2001 In early December along the Second Ring Road in Beijing to carry out all the current GSM and CDMA mobile phone network in transmitting power of the test. Test results show that the Second Ring Road in the CDMA mobile phone transmitting power for an average of 2.4 dBm (1.72mW), GSM mobile phones for an average of transmitting power 28.9dBm (773 mW), taking into account the GSM mobile phone only in the eighth time launch, GSM mobile phones In time of the equivalent average transmission power can be reduced to 19.85dBm (96.63mW). Thus see, CDMA mobile phones, the average transmission power equivalent to the GSM mobile phones in time of the transmitting power of the equivalent average 1.78 percent.
One, CDMA and GSM mobile phone system for transmitting power requirements compared
Let us take a look at CDMA and GSM mobile phone-related technical specifications of the transmitting power. At present, the widespread use of the 900MHz band GSM phone to launch the largest power 2W (33dBm), 1800MHz band launched the largest power 1W (30dBm), at the same time standardize requirements for 1800 and the GSM900 band, the smallest mobile phone communications in the process of transmitting power can not be lower than the respective 5dBm And 0dBm. CDMA IS-95A specification of the largest mobile phone transmission power requirements for 0.2W ~ 1W (23dBm ~ 30dBm), currently allow mobile phone networks in fact launched the largest power 23dBm (0.2W), specification of the CDMA mobile phone does not require a minimum transmission power.
In practice, communication, in a moment of a place, the actual cell phone transmitting power depends on the environment, quality of the communication system requirements, voice-activated, and other factors, the fact is that the system depends on the link budget. In the usual network design and planning, for the wrong frame rate is basically the same request, GSM base station system requirements to reach the mobile phone signals contained in the dry than usual for about 9dB, as the CDMA system uses spread-spectrum technology, spread-spectrum-wide rate of gain The coding gain of 21dB, (other low rate codes gain greater), the expansion of the solution containing the equivalent of the pre-signal ratio is less than the requirements of-14dB! (CDMA systems usually have to signal de-spread after the value of 7dB Or so).
Now let's compare the GSM and CDMA mobile phone transmission power of the initial value of fixed access and power control mechanisms. Phone and communications systems can be divided into two phases, the first phase of the access, the second phase of the communications traffic. For GSM systems, mobile phones in the random access into the special stage no previous model, there is no power control, in order to ensure the success of access, mobile phone system in order to allow the launch of the largest power (usually the biggest cell phone transmitting power). In the exclusive distribution channel (SDCCH or TCH), the mobile phone base stations in accordance with the instructions to adjust the phone transmitting power to adjust the step is usually to 2dB. Adjust the frequency for the first time 60ms.
The CDMA system, in the random access mode, the phone will be based on the received signal base level is estimated that a small initial value as a cell phone transmitting power, sending the first Access Probe, if within the required timeframe has not been The response base stations, mobile phones will increase the transmitting power, sending the second Access Probe, if within the specified time has not yet been a response to the information base stations, mobile phones will increase the transmitting power. Repeat this process until the station received a response or set up to try to reach the number of times so far. Call in the state, each 1.25ms mobile phone base stations to send a power control order, phone order increase or reduce their transmitting power to step 1dB.
By the above comparison, we can see that taking into account the CDMA system, unique to other technologies, such as soft switches, RAKE receiver for the multi-path diversity, strong forward error correction algorithm for the uplink to improve the budget, and so on, CDMA mobile phone system for the transmission power requirements than the GSM mobile phone system launched Gong's request to be much smaller. The GSM mobile phone access in the course of the greatest power to launch a call in the course of power control is slow, so the phone to a greater probability of high-power launch. CDMA mobile phone and a unique mechanism for random access and fast reverse power control, you can make the average cell phone transmitting power at a lower level. The above-mentioned in the conclusions qualitative analysis of the back of the actual measurement has been verified.
Second, the description of the road test and inspection results
Road test experiments carried out GSM and CDMA mobile phone communications in the actual process of transmitting power of the test. CDMA and GSM mobile phone test to test mobile phone dial 1861 at the same time, the car radio to adjust to the appropriate volume, analog two-way call. The speed of about 40km. GSM mobile phone once every 480ms sampling, CDMA mobile phones for every one sample of 20ms. The test measured the results are: CDMA mobile phone of the transmitting power for the average linear 2.4dBm (1.72 mW), with maximum power (23dBm, 0.2 watts) launched a probability of 0.2%; GSM mobile phone transmission power for the average linear 28.9dBm (773 mW), with maximum power (2 watts W) launched a probability of 21.8 percent. It is worth noting that at present Beijing Beijing's GSM mobile network has reached a mature state, a smaller distance between the base station, GSM phones can be fired less power, and the CDMA network in a stage of development, network optimization, CDMA mobile phones for transmitting power requirements will be more Small.
Third, mobile phone radiation safety standards for mobile phones and transmitting power
Cell phone radiation on human body under constant observation and research, a large number of foreign contradictory studies, there are no comprehensive scientific conclusions. At present, the international community (including the United States FCC, NCRP, the European CENEIEC) standard is widely used by the SAR values (SPECIFIC ABSORPTION RATE), it refers to the quality of the units in the human body's absorption of RF power. (Abbreviated formula)
As the phone calls when people close to the brain (without headphones), the mobile phone antenna radiation and the distance between the human brain is usually less than 15cm. Human brain in the near-field antenna radiation, because of the complexity of the organizational structure of the body, theoretically antenna radiation in the human body with the power distribution market is very difficult relationship. However, according to the theory of electromagnetic fields, one thing is certain, as well as the structure of the cell phone antenna in the human body and the relative position of certain cases, the larger the antenna output power, the human body in the form of higher electric field strength, the human body to absorb the greater the power of radio frequency radiation . At present, measuring the value of SAR is an important method is the use of human tissue equivalent model of the probe to measure the use of radio frequency radiation by the body of the actual value of the field.
SAR to the more stringent requirements of the FCC standard, 30MHz-15GHz band has recommended two types of radiation:
1. Controlled radiation limits:
0.4mw / g (average human body), the peak 8mw / g (for 1 gram of any human tissue on average), the average time for 6 minutes;
2. Controlled by non-radiation limits
0.08mw / g (average human body), the peak 1.6mw / g (for 1 gram of any human tissue on average), with an average time of 30 minutes.
Radioactive belong cell phones were beyond the control of sources of non-controlled radio frequency radiation.
That needs to be noted that the current cell phone SAR test results are in the mobile phone in order to launch the largest power and rate of movement of the whole case on that. The largest CDMA mobile phones for transmitting power 0.2W, GSM handsets launched the largest power 2W, but only in the GSM mobile phone 1 / 8 launch time, and the determination of the value of the SAR is a long time, the average, therefore, GSM and CDMA mobile phones in Under such circumstances similar to the value of the SAR is not surprising. We can not limit in such cases, GSM and CDMA mobile phone SAR value rather arbitrary and that the actual process of communication CDMA and GSM mobile phone radiation are similar. In practice, because in the process of communication, GSM and CDMA mobile phones are not always the greatest power in order to launch, in particular, CDMA mobile phones to full-rate, the maximum power of the launch of a very small probability. From the road in front of the test results of view, GSM mobile phones in order to launch high-power far greater than the probability of CDMA mobile phones launched by the probability of high-power, CDMA mobile phones, the average transmit power is far smaller than the largest CDMA mobile phone transmitting power, is far smaller GSM handsets in the average transmission power, so the actual communication in the course of the CDMA mobile phone radiation on the human body the actual value of the SAR will be much lower than the CDMA mobile phone of the SAR nominal value, but also much lower than the GSM mobile phone actual value of the SAR.
On the other hand, objectively speaking, the current widely used standard SAR may not be able to respond fully mobile phone radiation on the human body. Because the standards are based on electromagnetic radiation on the human body, the development of the thermal effect. In fact, electromagnetic waves, especially low-frequency pulse electromagnetic radiation on the human body's non-thermal effects are also increasingly a cause for concern, GSM mobile phones have launched low-frequency electromagnetic pulse has affected the sophisticated medical equipment, a hearing-aid device normal use, it is also harmful to the human body There is no conclusion. GSM mobile phone in order to avoid the above-mentioned shortcomings, the third-generation mobile communications system terminals will be launched CDMA mobile phones are the same as for the pulse of radio waves instead of radio waves.
As the technology of CDMA and GSM systems for GSM and CDMA mobile phone transmitter power requirements as well as the transmitting power of the initial value of the check, as well as power control mechanisms will be different in the actual process of communication, CDMA mobile phones, the average transmit power is far lower than the GSM mobile phone The average transmission power. Now confirmed that the measured network, CDMA mobile phones, the average transmission power than the GSM mobile phone transmission power 500 times smaller, taking into account the GSM mobile phone only in the eighth time launch at the same time, CDMA radiation energy than the GSM mobile phone radiation Little more than 60 times the energy.
Cell phone radiation safety standards in the SAR value of mobile phones in order to launch the largest power of the draw, in this case, GSM and CDMA mobile phone SAR value is quite normal. As the CDMA mobile phone communications in the actual process is far less than the average transmission power of the largest CDMA mobile phone transmitting power, far less than the average GSM phone transmitting power, the CDMA mobile phone radiation on the human body is far below the actual launch of the largest mobile phone power Under the SAR value, but also in the process of using low-frequency radio wave radiation is not, CDMA mobile phones are truly "green phone"!
What GSM and CDMA mobile phone radiation power who is who in small or big difference, in order to arrive at an objective comparison of the actual results, by a well-known international authority of the CDMA technology and a well-known domestic GSM network optimization company engineers and technicians in 2001 In early December along the Second Ring Road in Beijing to carry out all the current GSM and CDMA mobile phone network in transmitting power of the test. Test results show that the Second Ring Road in the CDMA mobile phone transmitting power for an average of 2.4 dBm (1.72mW), GSM mobile phones for an average of transmitting power 28.9dBm (773 mW), taking into account the GSM mobile phone only in the eighth time launch, GSM mobile phones In time of the equivalent average transmission power can be reduced to 19.85dBm (96.63mW). Thus see, CDMA mobile phones, the average transmission power equivalent to the GSM mobile phones in time of the transmitting power of the equivalent average 1.78 percent.
One, CDMA and GSM mobile phone system for transmitting power requirements compared
Let us take a look at CDMA and GSM mobile phone-related technical specifications of the transmitting power. At present, the widespread use of the 900MHz band GSM phone to launch the largest power 2W (33dBm), 1800MHz band launched the largest power 1W (30dBm), at the same time standardize requirements for 1800 and the GSM900 band, the smallest mobile phone communications in the process of transmitting power can not be lower than the respective 5dBm And 0dBm. CDMA IS-95A specification of the largest mobile phone transmission power requirements for 0.2W ~ 1W (23dBm ~ 30dBm), currently allow mobile phone networks in fact launched the largest power 23dBm (0.2W), specification of the CDMA mobile phone does not require a minimum transmission power.
In practice, communication, in a moment of a place, the actual cell phone transmitting power depends on the environment, quality of the communication system requirements, voice-activated, and other factors, the fact is that the system depends on the link budget. In the usual network design and planning, for the wrong frame rate is basically the same request, GSM base station system requirements to reach the mobile phone signals contained in the dry than usual for about 9dB, as the CDMA system uses spread-spectrum technology, spread-spectrum-wide rate of gain The coding gain of 21dB, (other low rate codes gain greater), the expansion of the solution containing the equivalent of the pre-signal ratio is less than the requirements of-14dB! (CDMA systems usually have to signal de-spread after the value of 7dB Or so).
Now let's compare the GSM and CDMA mobile phone transmission power of the initial value of fixed access and power control mechanisms. Phone and communications systems can be divided into two phases, the first phase of the access, the second phase of the communications traffic. For GSM systems, mobile phones in the random access into the special stage no previous model, there is no power control, in order to ensure the success of access, mobile phone system in order to allow the launch of the largest power (usually the biggest cell phone transmitting power). In the exclusive distribution channel (SDCCH or TCH), the mobile phone base stations in accordance with the instructions to adjust the phone transmitting power to adjust the step is usually to 2dB. Adjust the frequency for the first time 60ms.
The CDMA system, in the random access mode, the phone will be based on the received signal base level is estimated that a small initial value as a cell phone transmitting power, sending the first Access Probe, if within the required timeframe has not been The response base stations, mobile phones will increase the transmitting power, sending the second Access Probe, if within the specified time has not yet been a response to the information base stations, mobile phones will increase the transmitting power. Repeat this process until the station received a response or set up to try to reach the number of times so far. Call in the state, each 1.25ms mobile phone base stations to send a power control order, phone order increase or reduce their transmitting power to step 1dB.
By the above comparison, we can see that taking into account the CDMA system, unique to other technologies, such as soft switches, RAKE receiver for the multi-path diversity, strong forward error correction algorithm for the uplink to improve the budget, and so on, CDMA mobile phone system for the transmission power requirements than the GSM mobile phone system launched Gong's request to be much smaller. The GSM mobile phone access in the course of the greatest power to launch a call in the course of power control is slow, so the phone to a greater probability of high-power launch. CDMA mobile phone and a unique mechanism for random access and fast reverse power control, you can make the average cell phone transmitting power at a lower level. The above-mentioned in the conclusions qualitative analysis of the back of the actual measurement has been verified.
Second, the description of the road test and inspection results
Road test experiments carried out GSM and CDMA mobile phone communications in the actual process of transmitting power of the test. CDMA and GSM mobile phone test to test mobile phone dial 1861 at the same time, the car radio to adjust to the appropriate volume, analog two-way call. The speed of about 40km. GSM mobile phone once every 480ms sampling, CDMA mobile phones for every one sample of 20ms. The test measured the results are: CDMA mobile phone of the transmitting power for the average linear 2.4dBm (1.72 mW), with maximum power (23dBm, 0.2 watts) launched a probability of 0.2%; GSM mobile phone transmission power for the average linear 28.9dBm (773 mW), with maximum power (2 watts W) launched a probability of 21.8 percent. It is worth noting that at present Beijing Beijing's GSM mobile network has reached a mature state, a smaller distance between the base station, GSM phones can be fired less power, and the CDMA network in a stage of development, network optimization, CDMA mobile phones for transmitting power requirements will be more Small.
Third, mobile phone radiation safety standards for mobile phones and transmitting power
Cell phone radiation on human body under constant observation and research, a large number of foreign contradictory studies, there are no comprehensive scientific conclusions. At present, the international community (including the United States FCC, NCRP, the European CENEIEC) standard is widely used by the SAR values (SPECIFIC ABSORPTION RATE), it refers to the quality of the units in the human body's absorption of RF power. (Abbreviated formula)
As the phone calls when people close to the brain (without headphones), the mobile phone antenna radiation and the distance between the human brain is usually less than 15cm. Human brain in the near-field antenna radiation, because of the complexity of the organizational structure of the body, theoretically antenna radiation in the human body with the power distribution market is very difficult relationship. However, according to the theory of electromagnetic fields, one thing is certain, as well as the structure of the cell phone antenna in the human body and the relative position of certain cases, the larger the antenna output power, the human body in the form of higher electric field strength, the human body to absorb the greater the power of radio frequency radiation . At present, measuring the value of SAR is an important method is the use of human tissue equivalent model of the probe to measure the use of radio frequency radiation by the body of the actual value of the field.
SAR to the more stringent requirements of the FCC standard, 30MHz-15GHz band has recommended two types of radiation:
1. Controlled radiation limits:
0.4mw / g (average human body), the peak 8mw / g (for 1 gram of any human tissue on average), the average time for 6 minutes;
2. Controlled by non-radiation limits
0.08mw / g (average human body), the peak 1.6mw / g (for 1 gram of any human tissue on average), with an average time of 30 minutes.
Radioactive belong cell phones were beyond the control of sources of non-controlled radio frequency radiation.
That needs to be noted that the current cell phone SAR test results are in the mobile phone in order to launch the largest power and rate of movement of the whole case on that. The largest CDMA mobile phones for transmitting power 0.2W, GSM handsets launched the largest power 2W, but only in the GSM mobile phone 1 / 8 launch time, and the determination of the value of the SAR is a long time, the average, therefore, GSM and CDMA mobile phones in Under such circumstances similar to the value of the SAR is not surprising. We can not limit in such cases, GSM and CDMA mobile phone SAR value rather arbitrary and that the actual process of communication CDMA and GSM mobile phone radiation are similar. In practice, because in the process of communication, GSM and CDMA mobile phones are not always the greatest power in order to launch, in particular, CDMA mobile phones to full-rate, the maximum power of the launch of a very small probability. From the road in front of the test results of view, GSM mobile phones in order to launch high-power far greater than the probability of CDMA mobile phones launched by the probability of high-power, CDMA mobile phones, the average transmit power is far smaller than the largest CDMA mobile phone transmitting power, is far smaller GSM handsets in the average transmission power, so the actual communication in the course of the CDMA mobile phone radiation on the human body the actual value of the SAR will be much lower than the CDMA mobile phone of the SAR nominal value, but also much lower than the GSM mobile phone actual value of the SAR.
On the other hand, objectively speaking, the current widely used standard SAR may not be able to respond fully mobile phone radiation on the human body. Because the standards are based on electromagnetic radiation on the human body, the development of the thermal effect. In fact, electromagnetic waves, especially low-frequency pulse electromagnetic radiation on the human body's non-thermal effects are also increasingly a cause for concern, GSM mobile phones have launched low-frequency electromagnetic pulse has affected the sophisticated medical equipment, a hearing-aid device normal use, it is also harmful to the human body There is no conclusion. GSM mobile phone in order to avoid the above-mentioned shortcomings, the third-generation mobile communications system terminals will be launched CDMA mobile phones are the same as for the pulse of radio waves instead of radio waves.
As the technology of CDMA and GSM systems for GSM and CDMA mobile phone transmitter power requirements as well as the transmitting power of the initial value of the check, as well as power control mechanisms will be different in the actual process of communication, CDMA mobile phones, the average transmit power is far lower than the GSM mobile phone The average transmission power. Now confirmed that the measured network, CDMA mobile phones, the average transmission power than the GSM mobile phone transmission power 500 times smaller, taking into account the GSM mobile phone only in the eighth time launch at the same time, CDMA radiation energy than the GSM mobile phone radiation Little more than 60 times the energy.
Cell phone radiation safety standards in the SAR value of mobile phones in order to launch the largest power of the draw, in this case, GSM and CDMA mobile phone SAR value is quite normal. As the CDMA mobile phone communications in the actual process is far less than the average transmission power of the largest CDMA mobile phone transmitting power, far less than the average GSM phone transmitting power, the CDMA mobile phone radiation on the human body is far below the actual launch of the largest mobile phone power Under the SAR value, but also in the process of using low-frequency radio wave radiation is not, CDMA mobile phones are truly "green phone"!
Classification of mobile communication technology
There are a variety of mobile communication system classification. For example, according to the nature of the signal can be divided into analog, digital; according to the modulation, can be divided into FM, PM, AM; by way of connecting multiple access points can be divided into:
Frequency division multiple access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA).
Than the simulation of GSM mobile phones have great advantages, but in the spectrum efficiency of the simulator is only three times a limited capacity; in the voice quality is also very difficult to achieve the level of telephone cable; TDMA terminal access to the highest rate can only be achieved 9.6kbit / s; TDMA system with soft-switch function, and thus easy to dropped calls, the impact on the quality of service. Therefore, TDMA is not a modern cellular mobile communication the best wireless access, and CDMA multiple access technology for fully modern mobile communications network as required by high-capacity, high-quality, integrated services, such as soft switches, is being more and more Operators and users of all ages.
Frequency division multiple access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA).
Than the simulation of GSM mobile phones have great advantages, but in the spectrum efficiency of the simulator is only three times a limited capacity; in the voice quality is also very difficult to achieve the level of telephone cable; TDMA terminal access to the highest rate can only be achieved 9.6kbit / s; TDMA system with soft-switch function, and thus easy to dropped calls, the impact on the quality of service. Therefore, TDMA is not a modern cellular mobile communication the best wireless access, and CDMA multiple access technology for fully modern mobile communications network as required by high-capacity, high-quality, integrated services, such as soft switches, is being more and more Operators and users of all ages.
CDMA technology holding point
1. CDMA is a spread spectrum communication, he has a spread spectrum communication of the following characteristics:
(1) anti-interference ability. This is the basic feature of spread spectrum communications, all communication is second to none.
(2) broadband transmission, anti-fading ability.
(3) As a result of broadband transmission, the channel of transmission of the useful signal power than the interference signal power is much lower, so it seems hidden in the noise signal in; that is, if power density is relatively low, in favor of covert signals.
(4) the use of spread spectrum code of relevance to the user's access to information intercepted by anti-capacity of the strong.
(5) to receive multiple users at the same time, to send the same time.
2. In the CDMA spread spectrum communication system, the introduction of new technology with some of the key new features:
(1) uses a variety of ways diversity. In addition to the traditional outer space diversity. As broadband transmission frequency diversity has played a role, at the same time in the base station and mobile station using the RAKE receiver technology, which is equivalent to the time diversity.
(2) the use of voice-activated technology and technology sector. Because the capacity of the CDMA system directly related to the disruption of the use of voice-activated technology sector and reduce interference, can increase the capacity of the system as a whole.
(3) the use of mobile station-assisted soft-switch. It can be achieved through the seamless switch to ensure the continuity of the call, reducing dropped calls. The switch in the region through the mobile station set to receive a number of sub-base of the signal can reduce their transmitting power, thereby reducing interference on the surrounding base stations, which will help improve the reverse way of joint coverage and capacity.
(4) the use of power control technology, this reduces the transmission power stabilization.
(5) has a capacity of soft features. In the peak traffic by raising false frame rate can be used to increase the number of channels. When the load cell adjacent to a light-weight, the weight of the load cell can reduce the transmission power of the pilot, so that users on the edge of the area due to the pilot's lack of intensity switch to the adjacent cell, so that the burden-sharing.
(6), good compatibility. CDMA because of the large bandwidth, the distribution of power in a broad spectrum, the power density so low, narrow-band interference simulation system of small, so the two can co-exist. That is, good compatibility.
(7) CDMA frequency utilization of high frequency without planning, which is one of the characteristics of CDMA.
(8) CDMA voice OCELP efficient coding. Voice encoding digital communications technology is an important issue. OCELP is the use of the code table VQ difference signal, and voice-activated in accordance with the degree of a variable rate of output signal. This sort of five-way horse is considered to be currently the most efficient encoding technology, ensuring a better quality of voice, greatly enhanced the capacity of the system. This vocoder with 8kbit / S and 13kbit / S sequences of the two rates. 8kbit / S sequence from 1.2kbit / s to 9.6kbit / s variable, 13kbit / S sequence from 1.8kbt / s to 14.4kbt / S variable. Recently, a well-8kbit/sEVRC encoders available, with 8kbit / s vocoder capacity of the characteristics of voice quality has been improved.
(1) anti-interference ability. This is the basic feature of spread spectrum communications, all communication is second to none.
(2) broadband transmission, anti-fading ability.
(3) As a result of broadband transmission, the channel of transmission of the useful signal power than the interference signal power is much lower, so it seems hidden in the noise signal in; that is, if power density is relatively low, in favor of covert signals.
(4) the use of spread spectrum code of relevance to the user's access to information intercepted by anti-capacity of the strong.
(5) to receive multiple users at the same time, to send the same time.
2. In the CDMA spread spectrum communication system, the introduction of new technology with some of the key new features:
(1) uses a variety of ways diversity. In addition to the traditional outer space diversity. As broadband transmission frequency diversity has played a role, at the same time in the base station and mobile station using the RAKE receiver technology, which is equivalent to the time diversity.
(2) the use of voice-activated technology and technology sector. Because the capacity of the CDMA system directly related to the disruption of the use of voice-activated technology sector and reduce interference, can increase the capacity of the system as a whole.
(3) the use of mobile station-assisted soft-switch. It can be achieved through the seamless switch to ensure the continuity of the call, reducing dropped calls. The switch in the region through the mobile station set to receive a number of sub-base of the signal can reduce their transmitting power, thereby reducing interference on the surrounding base stations, which will help improve the reverse way of joint coverage and capacity.
(4) the use of power control technology, this reduces the transmission power stabilization.
(5) has a capacity of soft features. In the peak traffic by raising false frame rate can be used to increase the number of channels. When the load cell adjacent to a light-weight, the weight of the load cell can reduce the transmission power of the pilot, so that users on the edge of the area due to the pilot's lack of intensity switch to the adjacent cell, so that the burden-sharing.
(6), good compatibility. CDMA because of the large bandwidth, the distribution of power in a broad spectrum, the power density so low, narrow-band interference simulation system of small, so the two can co-exist. That is, good compatibility.
(7) CDMA frequency utilization of high frequency without planning, which is one of the characteristics of CDMA.
(8) CDMA voice OCELP efficient coding. Voice encoding digital communications technology is an important issue. OCELP is the use of the code table VQ difference signal, and voice-activated in accordance with the degree of a variable rate of output signal. This sort of five-way horse is considered to be currently the most efficient encoding technology, ensuring a better quality of voice, greatly enhanced the capacity of the system. This vocoder with 8kbit / S and 13kbit / S sequences of the two rates. 8kbit / S sequence from 1.2kbit / s to 9.6kbit / s variable, 13kbit / S sequence from 1.8kbt / s to 14.4kbt / S variable. Recently, a well-8kbit/sEVRC encoders available, with 8kbit / s vocoder capacity of the characteristics of voice quality has been improved.
The advantages of CDMA
(1) system capacity
In theory, using the same frequency resources, CDMA mobile network than the analog network capacity 20 times more than in the actual use of large analog network 10 times larger than 4-5 times that of GSM.
(2) capacity of the system configuration flexibility
In the CDMA system, the increase in the number of users is equivalent to an increase in background noise, resulting in a decline in voice quality. However, There is no limit on the number of users, operators can be among the capacity and voice quality to consider a compromise. In addition, the small number of traffic between and interference based on auto-balance.
The characteristics of CDMA and the relevant mechanism. CDMA is a disturbance from the system, all mobile users occupy the same frequency and bandwidth, an analogy, the bandwidth will be thought of a big house and all the people who will be the only big house. If they use a completely different language, they can clearly hear his voice only be from some other people's interference. Here, the room air can be thought of as broadband carrier, and different languages were used as codes, we can increase user constant background noise until the entire restrict us. If the user can control the signal strength, while maintaining high-quality calls at the same time, we will be able to accommodate more users.
(3) better call quality
TDMA channel structure can only support 4Kb voice encoder, it can not support more than 8Kb voice encoder. CDMA and the structure can support voice 13kb encoder. Can provide better call quality. CDMA vocoder system can dynamically adjust the data transfer rate, and in accordance with the appropriate threshold choose a different grade level launch. At the same time, according to background noise threshold of change and change so that even in the larger background noise, can get a better call quality. In addition, TDMA uses a hard-handed manner, the user can clearly feel the call of the interruption in user-intensive, base stations in the city, especially on the continuity of this, because in such areas occur every 2 minutes to 4 transfer. The CDMA system, "dropped calls" significant reduction, CDMA system uses a soft-switch technology, "and then connect to disconnect," so hard to switch completely to overcome the shortcomings of dropped calls easily.
(4) simple frequency planning
By the user to distinguish between different code sequences, it is not the same CDMA carrier in the adjacent residential use, flexible network planning, expansion simple.
(5) low-cost network
CDMA cellular technology in each and every part of the same frequency, to simplify the planning system as a whole, without lowering traffic situations to reduce the number of sites needed to reduce the deployment and operation costs. CDMA network coverage, high-capacity system required a small base station, reduces the cost of network building.
CDMA digital mobile technology and is now well-known GSM digital mobile systems. Simulation technology, known as the first generation of mobile phone technology, GSM is a second-generation, CDMA is a second-generation mobile communication technology and a half, more advanced than GSM.
In theory, using the same frequency resources, CDMA mobile network than the analog network capacity 20 times more than in the actual use of large analog network 10 times larger than 4-5 times that of GSM.
(2) capacity of the system configuration flexibility
In the CDMA system, the increase in the number of users is equivalent to an increase in background noise, resulting in a decline in voice quality. However, There is no limit on the number of users, operators can be among the capacity and voice quality to consider a compromise. In addition, the small number of traffic between and interference based on auto-balance.
The characteristics of CDMA and the relevant mechanism. CDMA is a disturbance from the system, all mobile users occupy the same frequency and bandwidth, an analogy, the bandwidth will be thought of a big house and all the people who will be the only big house. If they use a completely different language, they can clearly hear his voice only be from some other people's interference. Here, the room air can be thought of as broadband carrier, and different languages were used as codes, we can increase user constant background noise until the entire restrict us. If the user can control the signal strength, while maintaining high-quality calls at the same time, we will be able to accommodate more users.
(3) better call quality
TDMA channel structure can only support 4Kb voice encoder, it can not support more than 8Kb voice encoder. CDMA and the structure can support voice 13kb encoder. Can provide better call quality. CDMA vocoder system can dynamically adjust the data transfer rate, and in accordance with the appropriate threshold choose a different grade level launch. At the same time, according to background noise threshold of change and change so that even in the larger background noise, can get a better call quality. In addition, TDMA uses a hard-handed manner, the user can clearly feel the call of the interruption in user-intensive, base stations in the city, especially on the continuity of this, because in such areas occur every 2 minutes to 4 transfer. The CDMA system, "dropped calls" significant reduction, CDMA system uses a soft-switch technology, "and then connect to disconnect," so hard to switch completely to overcome the shortcomings of dropped calls easily.
(4) simple frequency planning
By the user to distinguish between different code sequences, it is not the same CDMA carrier in the adjacent residential use, flexible network planning, expansion simple.
(5) low-cost network
CDMA cellular technology in each and every part of the same frequency, to simplify the planning system as a whole, without lowering traffic situations to reduce the number of sites needed to reduce the deployment and operation costs. CDMA network coverage, high-capacity system required a small base station, reduces the cost of network building.
CDMA digital mobile technology and is now well-known GSM digital mobile systems. Simulation technology, known as the first generation of mobile phone technology, GSM is a second-generation, CDMA is a second-generation mobile communication technology and a half, more advanced than GSM.
GSM communication system
GSM system (Global System for Mobile Communication), also known as Global System for Mobile Communications (GSM).
GSM mobile communication system is mainly to exchange sub-system (MSS), Base Station Subsystem (BSS) and mobile station (MS) has three major components, as shown. BSS and MSS in which the interface between A for the interface, BSS and the interface between the MS for the Um interface. GSM specification of the system interface and the A's have a clear interface Um, that is to say, A and the interface Um interface is an open interface.
(4) GSM system
(4) -1. Mobile Switching subsystem MSS
To complete the exchange of information, information management, follow-up call, the number of management functions.
(4) -2. BSS Base Station Subsystem
BSS is a certain system of wireless coverage in areas controlled by the MSC, MS communicate with the system, the completion of the distribution channel, the user's access and paging, information transmission and other functions.
(4) -3. Mobile Station MS
MS is a GSM mobile system equipment, which is composed of two parts, mobile terminals and customer identification card (SIM card). Mobile terminal "machine", it can complete the voice coding, channel coding, information encryption, modulation and demodulation of the information, transmitting and receiving information. SIM card is the "people", which we are similar to those used by IC cards, also known as smart cards, customer identification requirements for certification have all the information and the implementation of some of the secrecy and security-related information in order to prevent illegal customer Access to the Internet. SIM cards can also store and network management and customer-related data, only to insert SIM card mobile terminals can access into the net.
(4) -4. Operation and Maintenance System
GSM sub-system also includes operation and maintenance sub-system (OMC), the entire GSM network management and monitoring. Through the achievement of its GSM network in various parts of the functions of surveillance, the report states, the fault diagnosis functions.
A) GSM network system
GSM's history can be traced back to 1982, at the time, the four countries to the Nordic CEPT (Conference Europe of Post and Telecommunications) submitted a proposal that calls for 900MHZ band of European norms of public telecommunication services in order to create a unified pan-European cellular systems. In the same year, set up a special team to mobile communications (GSM-Group Special Mobile). In the 1982 ~ 1985, the focus of discussion is the development of analog cellular networks or the development of standards for digital cellular network standards, until the decision in 1986 to develop standards for digital cellular network. In 1986, in Paris for different companies, different options of the system (8) were compared, including on-site test. May 1987 selection of narrow-band TDMA program. At the same time, 18 countries signed a memorandum of understanding with each other to reach an agreement to fulfill the norms. In 1988 promulgated the GSM standard, also known as the pan-European digital cellular communications standard. At this stage, GSM has two parallel systems: GSM900 and DCS1800, the two systems function the same as the frequency is different. In the GSM recommendations, did not provide the hardware, only to the development of feature Interface and detailed provisions to facilitate such different products to communicate with each other. A total of 12 recommendations GSM system.
The main components of the system 1.GSM
GSM digital cellular communication system can be divided into the main part of the mobile station, base station subsystems and network subsystems. Base Station Subsystem (the base station BS) from the base station transceivers Taiwan (BTS) and base station controller (BSC) component; network sub-system by the Mobile Switching Center (MSC) and Operation and Maintenance Center (OMC) as well as the location of the site Register (HLR), visit Location Register (VLR), Authentication Center (AUC) and equipment register marks (EIR), and other components.
2.GSM the region, number, address and identification
1) region
From the geographical scope of view, GSM system is divided into GSM service area, public land mobile network (PLMN) business areas, Mobile Switching Control Area (MSC area), the location of the area (LA), base stations and residential areas.
* GSM service area
By all members of the GSM network, mobile services in the region as long as the user, the system will be able to get a variety of services, including the completion of the international roaming.
GSM mobile communication system is mainly to exchange sub-system (MSS), Base Station Subsystem (BSS) and mobile station (MS) has three major components, as shown. BSS and MSS in which the interface between A for the interface, BSS and the interface between the MS for the Um interface. GSM specification of the system interface and the A's have a clear interface Um, that is to say, A and the interface Um interface is an open interface.
(4) GSM system
(4) -1. Mobile Switching subsystem MSS
To complete the exchange of information, information management, follow-up call, the number of management functions.
(4) -2. BSS Base Station Subsystem
BSS is a certain system of wireless coverage in areas controlled by the MSC, MS communicate with the system, the completion of the distribution channel, the user's access and paging, information transmission and other functions.
(4) -3. Mobile Station MS
MS is a GSM mobile system equipment, which is composed of two parts, mobile terminals and customer identification card (SIM card). Mobile terminal "machine", it can complete the voice coding, channel coding, information encryption, modulation and demodulation of the information, transmitting and receiving information. SIM card is the "people", which we are similar to those used by IC cards, also known as smart cards, customer identification requirements for certification have all the information and the implementation of some of the secrecy and security-related information in order to prevent illegal customer Access to the Internet. SIM cards can also store and network management and customer-related data, only to insert SIM card mobile terminals can access into the net.
(4) -4. Operation and Maintenance System
GSM sub-system also includes operation and maintenance sub-system (OMC), the entire GSM network management and monitoring. Through the achievement of its GSM network in various parts of the functions of surveillance, the report states, the fault diagnosis functions.
A) GSM network system
GSM's history can be traced back to 1982, at the time, the four countries to the Nordic CEPT (Conference Europe of Post and Telecommunications) submitted a proposal that calls for 900MHZ band of European norms of public telecommunication services in order to create a unified pan-European cellular systems. In the same year, set up a special team to mobile communications (GSM-Group Special Mobile). In the 1982 ~ 1985, the focus of discussion is the development of analog cellular networks or the development of standards for digital cellular network standards, until the decision in 1986 to develop standards for digital cellular network. In 1986, in Paris for different companies, different options of the system (8) were compared, including on-site test. May 1987 selection of narrow-band TDMA program. At the same time, 18 countries signed a memorandum of understanding with each other to reach an agreement to fulfill the norms. In 1988 promulgated the GSM standard, also known as the pan-European digital cellular communications standard. At this stage, GSM has two parallel systems: GSM900 and DCS1800, the two systems function the same as the frequency is different. In the GSM recommendations, did not provide the hardware, only to the development of feature Interface and detailed provisions to facilitate such different products to communicate with each other. A total of 12 recommendations GSM system.
The main components of the system 1.GSM
GSM digital cellular communication system can be divided into the main part of the mobile station, base station subsystems and network subsystems. Base Station Subsystem (the base station BS) from the base station transceivers Taiwan (BTS) and base station controller (BSC) component; network sub-system by the Mobile Switching Center (MSC) and Operation and Maintenance Center (OMC) as well as the location of the site Register (HLR), visit Location Register (VLR), Authentication Center (AUC) and equipment register marks (EIR), and other components.
2.GSM the region, number, address and identification
1) region
From the geographical scope of view, GSM system is divided into GSM service area, public land mobile network (PLMN) business areas, Mobile Switching Control Area (MSC area), the location of the area (LA), base stations and residential areas.
* GSM service area
By all members of the GSM network, mobile services in the region as long as the user, the system will be able to get a variety of services, including the completion of the international roaming.
CDMA systems knowledge
1 CDMA system concept
CDMA system is based on code division technology (Spread Spectrum) and multiple access technology, communication systems, the system for each user allocated address their specific code. Address code between each other quasi-orthogonal, in order to time, space and frequency can overlap; will be required to send the signal has a bandwidth of the data, with a bandwidth of the signal bandwidth is much larger than the pseudo-random code modulation, so that The original data signal bandwidth has been expanded to carry out the receiving end to the anti-process for expanding access, and enhanced anti-jamming capabilities.
CDMA systems belonging to the sub-interference system.
2 CDMA system:
0:00 systems: the definition at 0:00 on the January 6, 1980 for the whole system start-up time. Bias zero yards long and short code at the same time, at this time of the initial state
GPS base stations will be all the time even seconds of each start-up time (80ms or after the entire Department several times) as a PN code offset 0 (for the period 80 / 3 ms) at the beginning of the state, that is, before that happens to the output A "1" in a row and 15 "0" such a chip PN
All base stations will be required at 0:00 on the January 6, 1980 (GPS start-up time) as a long sequence of m-code at the beginning of (this happens before the output of a "1" chip in a row and 41 of the "0" Chip )
The use of GPS timing of benefits: fast switching, and simple synchronization.
3 CDMA system shortcomings:
From non-synchronous CDMA network in a different sequence spread spectrum users are not completely orthogonal, which led to the MAI;
Due to use the same carrier frequency, many users share the same channel, the signal of a weak signal inhibited, resulting in "far - close to the" effect of the impact of user calls.
CDMA system using power control technology "--- far into the" effect
CDMA system is based on code division technology (Spread Spectrum) and multiple access technology, communication systems, the system for each user allocated address their specific code. Address code between each other quasi-orthogonal, in order to time, space and frequency can overlap; will be required to send the signal has a bandwidth of the data, with a bandwidth of the signal bandwidth is much larger than the pseudo-random code modulation, so that The original data signal bandwidth has been expanded to carry out the receiving end to the anti-process for expanding access, and enhanced anti-jamming capabilities.
CDMA systems belonging to the sub-interference system.
2 CDMA system:
0:00 systems: the definition at 0:00 on the January 6, 1980 for the whole system start-up time. Bias zero yards long and short code at the same time, at this time of the initial state
GPS base stations will be all the time even seconds of each start-up time (80ms or after the entire Department several times) as a PN code offset 0 (for the period 80 / 3 ms) at the beginning of the state, that is, before that happens to the output A "1" in a row and 15 "0" such a chip PN
All base stations will be required at 0:00 on the January 6, 1980 (GPS start-up time) as a long sequence of m-code at the beginning of (this happens before the output of a "1" chip in a row and 41 of the "0" Chip )
The use of GPS timing of benefits: fast switching, and simple synchronization.
3 CDMA system shortcomings:
From non-synchronous CDMA network in a different sequence spread spectrum users are not completely orthogonal, which led to the MAI;
Due to use the same carrier frequency, many users share the same channel, the signal of a weak signal inhibited, resulting in "far - close to the" effect of the impact of user calls.
CDMA system using power control technology "--- far into the" effect
CDMA technology standards
CDMA technology standardization has gone through several stages. IS-95 standard series cdmaONE is the first release of the standards in the real world's widely used in the first CDMA standard is IS-95A, the standard encoding support for the 8K voice services. Were subsequently published a 13K voice encoder TSB74 standards, the CDMA PCS support for the 1.9GHz system STD-008 standard, in which encoding 13K voice quality of service has been very close to the wired telephone voice quality. With the mobile data business growth in demand, in February 1998, QUALCOMM Incorporated announced the IS-95B standards for CDMA-based platform. IS-95B will provide CDMA system performance and mobile users increase in the flow of data communications equipment to provide data services 64kbps. Later, cdma2000 become narrow-band CDMA system, the transition to third-generation systems. cdma2000 standards in the early stage of research, made 1X and 3X development strategy, but studies have shown that, 1X and 1X enhanced technology represents the future direction of development.
CDMA technology's standardization and promoting the application of technology in the world. At present, in the United States, South Korea, Japan and other countries, CDMA technology has been applied on a larger scale. In some European countries, some of the operators also set up a CDMA network. According to the CDG (the world's CDMA Development Group) statistics, CDMA subscribers by the end of 1996 was 1,000,000; to March 1998 has been the rapid growth to 10,000,000; As of September 1999, the number of users has more than 40,000,000. In early 2000, the world's CDMA mobile phone users has exceeded the total number of 50,000,000, a year in the number of users grew 118 percent. CDG said that Asia has become the CDMA market, the main engine of growth, Asia, the number of CDMA subscribers grew 88% from a year ago, reaching 28,000,000. The U.S. growth rate is as high as 143 percent, to 16,500,000, but the absolute number of users is lower than in Asia, the Asia-Pacific region, Hong Kong, China, Japan, South Korea, Australia, Thailand, India, the Philippines, New Zealand, Bangladesh and many other Countries and regions have established a CDMA commercial network, the number of users has more than 21,000,000. The third is located in the growth of Central and South America, CDMA subscribers reached 5,000,000. CDG has also said that from now on the global CDMA market, mainland China's largest area of growth potential, it is estimated that in 2003 the mainland Chinese market, the number of users who can be reached 40,000,000.
CDMA mobile communications technology development. In the 2G stage, CDMA and GSM Enhanced IS95A the technical system in the same generation of products, providing more or less the same business. However, CDMA technology has its own unique, good call quality, fewer dropped calls, low-level radiation, health and environmental protection have significant characteristics. In the 2.5G stage, CDMA2000 1X RTT and GPRS technology has been evident in the difference in the rate of transmission on 1X RTT higher than GPRS, carrying on business in the new 1X RTT mature than GPRS can offer more speed in the rate of new business . From 2.5G to 3G technologies on the transitional institutions, CDMA2000 1.X to CDMA20003.X than GPRS transition to a more smooth transition to WCDMA.
CDMA technology's standardization and promoting the application of technology in the world. At present, in the United States, South Korea, Japan and other countries, CDMA technology has been applied on a larger scale. In some European countries, some of the operators also set up a CDMA network. According to the CDG (the world's CDMA Development Group) statistics, CDMA subscribers by the end of 1996 was 1,000,000; to March 1998 has been the rapid growth to 10,000,000; As of September 1999, the number of users has more than 40,000,000. In early 2000, the world's CDMA mobile phone users has exceeded the total number of 50,000,000, a year in the number of users grew 118 percent. CDG said that Asia has become the CDMA market, the main engine of growth, Asia, the number of CDMA subscribers grew 88% from a year ago, reaching 28,000,000. The U.S. growth rate is as high as 143 percent, to 16,500,000, but the absolute number of users is lower than in Asia, the Asia-Pacific region, Hong Kong, China, Japan, South Korea, Australia, Thailand, India, the Philippines, New Zealand, Bangladesh and many other Countries and regions have established a CDMA commercial network, the number of users has more than 21,000,000. The third is located in the growth of Central and South America, CDMA subscribers reached 5,000,000. CDG has also said that from now on the global CDMA market, mainland China's largest area of growth potential, it is estimated that in 2003 the mainland Chinese market, the number of users who can be reached 40,000,000.
CDMA mobile communications technology development. In the 2G stage, CDMA and GSM Enhanced IS95A the technical system in the same generation of products, providing more or less the same business. However, CDMA technology has its own unique, good call quality, fewer dropped calls, low-level radiation, health and environmental protection have significant characteristics. In the 2.5G stage, CDMA2000 1X RTT and GPRS technology has been evident in the difference in the rate of transmission on 1X RTT higher than GPRS, carrying on business in the new 1X RTT mature than GPRS can offer more speed in the rate of new business . From 2.5G to 3G technologies on the transitional institutions, CDMA2000 1.X to CDMA20003.X than GPRS transition to a more smooth transition to WCDMA.
CDMA technology background
CDMA technology on human beings from the higher-quality wireless communications. During the Second World War as a result of the war on the needs of the research and development of CDMA technology, their original thinking is the enemy of one's own side to prevent interference with communications, during the war are widely used in anti-military communication, and later updated by QUALCOMM Incorporated to become commercial Cellular telecommunications technology. In 1995, the first commercial CDMA system later, CDMA technology's many advantages in theory in practice have been tested, which in North America, South America and Asia and other places have been quick to promote and applications. Many of the world's countries and regions, including Hong Kong, China, South Korea, Japan, the United States have established a CDMA commercial network. In the United States and Japan, CDMA has become the major domestic mobile communications technology. In the United States, 10 mobile communications company operating in 7 selected CDMA. In April this year, South Korea, 60% of the population into CDMA users. In Australia to host the 27th Olympic Games, CDMA technology is playing an important role in
CDMA definition of professional
CDMA is the abbreviation of Code Division Multiple Access, it is in digital technology branch - spread spectrum technology developed a new and sophisticated wireless communication technology. CDMA technology is based on the principle of spread spectrum technology, is about the need to send a certain signal bandwidth data, with a signal bandwidth is much larger than the bandwidth of high-speed pseudo-random code modulation, so that the original data signal bandwidth to be extended via modulation and Sent. The receiving end of exactly the same as the use of pseudo-random code, and to receive the signal bandwidth for processing related to the original broadband signal into data that is the narrow-band signal de-spread in order to achieve information and communication.
Wednesday, October 8, 2008
The development of GSM
In the mid-1980s, when the analog cellular mobile communication system on the market just when the world's developed countries in the development of second-generation mobile communication systems. One of the most representative and more mature standard of a pan-European GSM, the United States ADC (D-AMPS) and Japan JDC (now renamed the PDC), and other digital mobile communication system. These figures are in the system, GSM development of the most eye-catching. 1991 GSM system in Europe, the official launch, the network opened.
GSM family are GSM900, DCS1800 and PCS1900 three parts, between the main difference is that the work of the band's differences.
The emergence of cellular mobile communications can be described as a mobile communications revolution. Their frequency reuse greatly increased the frequency of utilization and increase system capacity, the intelligent network to achieve a cross-district transfer and roaming capabilities, expanded customer service area, but there are four of these simulated shortcomings of the system: no system Public interface; difficult to carry business data; spectrum utilization of low-capacity can not meet demand; security poor, vulnerable to eavesdropping and easy to do "fake machine." Especially in Europe there is no system of public interface with each other can not roam on a lot of inconvenience to customers.
GSM digital mobile communication systems from Europe. As early as 1982, Europe has several analog cellular mobile operators in the system, such as the Nordic countries of the NMT (Nordic Mobile Telephone) and the United Kingdom of TACS (all-access communication system), other Western European countries to provide mobile service. At that time, these systems is the system can not be used abroad. In order to facilitate the reunification of Europe-wide use of mobile phones, the need for a public system, in 1982, the Nordic countries to the CEPT (Europe Chief of the General Assembly of Posts and Telecommunications) submitted a proposal that calls for the 900MHz band of public norms of the European telecommunications business. At the General Assembly on the establishment of a European Telecommunications Standards Institute (ETSI) Technical Committee under the "mobile particular group (Group Special Mobile)", referred to as "GSM", to formulate standards and proposals.
Since our establishment in 1992 in Jiaxing and the opening of the first demonstration of GSM system, and in September 1993 officially open the business, all over the country's mobile communications system used in most of the GSM system, making GSM system to become China's most mature and market share The largest was a kind of digital cellular systems. As of November 2002, Chinese mobile phone users 200,000,000, 2001 at the end of the additional 55,092,000.
GSM system has several important features: good ability to copy security, network capacity, resource-rich mobile phone number, the call clear, strong stability are less vulnerable to interference, and sensitive information, talk less dead, low-power mobile phones.
At present, China's two main GSM system for the GSM 900 and GSM1800, due to the different frequencies, so the application of the phone are not the same. But the most fundamental is the dual-band mobile phone, the two are free to switch between frequency bands. European countries are widely used by the GSM900 and GSM1800 system, in addition to the other joined the GSM1900, for the tri-band mobile phone handset. With the mobile phone market in China's further development, is now also have a tri-band phone can be in the GSM900 \ GSM1800 \ GSM1900 band of the three free to switch cell phone, a cell phone really can be enjoyed throughout the world.
Early look at, GSM900 the development of an earlier time, the use of more GSM1800 On the other hand the development of late. Physical properties, the former lower-frequency spectrum, longer wavelength, low penetration, but the transmission distance, and cell phone transmitting power stronger, more power and therefore a shorter waiting time; and the latter's high frequency , A shorter wavelength, the penetrating power of good, but to send a short distance, the transmission power of mobile phones smaller, stand-by time is correspondingly longer.
Emergency call system, GSM is the voice of a specific business function. Even in the GSM mobile phone to set the limit has not expired and insert SIM cards (SIM), as long as the GSM network coverage in the region, only the press of a button the user can be pre-determined number of special (such as 110, 119,120 and so on) sent to the appropriate units (police, fire brigade, first aid centers, etc.). This simplified approach is to dial in an emergency moment too late to carry out complex operations and specially designed.
GSM family are GSM900, DCS1800 and PCS1900 three parts, between the main difference is that the work of the band's differences.
The emergence of cellular mobile communications can be described as a mobile communications revolution. Their frequency reuse greatly increased the frequency of utilization and increase system capacity, the intelligent network to achieve a cross-district transfer and roaming capabilities, expanded customer service area, but there are four of these simulated shortcomings of the system: no system Public interface; difficult to carry business data; spectrum utilization of low-capacity can not meet demand; security poor, vulnerable to eavesdropping and easy to do "fake machine." Especially in Europe there is no system of public interface with each other can not roam on a lot of inconvenience to customers.
GSM digital mobile communication systems from Europe. As early as 1982, Europe has several analog cellular mobile operators in the system, such as the Nordic countries of the NMT (Nordic Mobile Telephone) and the United Kingdom of TACS (all-access communication system), other Western European countries to provide mobile service. At that time, these systems is the system can not be used abroad. In order to facilitate the reunification of Europe-wide use of mobile phones, the need for a public system, in 1982, the Nordic countries to the CEPT (Europe Chief of the General Assembly of Posts and Telecommunications) submitted a proposal that calls for the 900MHz band of public norms of the European telecommunications business. At the General Assembly on the establishment of a European Telecommunications Standards Institute (ETSI) Technical Committee under the "mobile particular group (Group Special Mobile)", referred to as "GSM", to formulate standards and proposals.
Since our establishment in 1992 in Jiaxing and the opening of the first demonstration of GSM system, and in September 1993 officially open the business, all over the country's mobile communications system used in most of the GSM system, making GSM system to become China's most mature and market share The largest was a kind of digital cellular systems. As of November 2002, Chinese mobile phone users 200,000,000, 2001 at the end of the additional 55,092,000.
GSM system has several important features: good ability to copy security, network capacity, resource-rich mobile phone number, the call clear, strong stability are less vulnerable to interference, and sensitive information, talk less dead, low-power mobile phones.
At present, China's two main GSM system for the GSM 900 and GSM1800, due to the different frequencies, so the application of the phone are not the same. But the most fundamental is the dual-band mobile phone, the two are free to switch between frequency bands. European countries are widely used by the GSM900 and GSM1800 system, in addition to the other joined the GSM1900, for the tri-band mobile phone handset. With the mobile phone market in China's further development, is now also have a tri-band phone can be in the GSM900 \ GSM1800 \ GSM1900 band of the three free to switch cell phone, a cell phone really can be enjoyed throughout the world.
Early look at, GSM900 the development of an earlier time, the use of more GSM1800 On the other hand the development of late. Physical properties, the former lower-frequency spectrum, longer wavelength, low penetration, but the transmission distance, and cell phone transmitting power stronger, more power and therefore a shorter waiting time; and the latter's high frequency , A shorter wavelength, the penetrating power of good, but to send a short distance, the transmission power of mobile phones smaller, stand-by time is correspondingly longer.
Emergency call system, GSM is the voice of a specific business function. Even in the GSM mobile phone to set the limit has not expired and insert SIM cards (SIM), as long as the GSM network coverage in the region, only the press of a button the user can be pre-determined number of special (such as 110, 119,120 and so on) sent to the appropriate units (police, fire brigade, first aid centers, etc.). This simplified approach is to dial in an emergency moment too late to carry out complex operations and specially designed.
GSM characteristics
1.GSM on the use of intuitive features:
GSM system has several important features: good ability to copy security, network capacity, resource-rich mobile phone number, the call clear, strong stability are less vulnerable to interference, and sensitive information, talk less dead, low-power mobile phones.
2.GSM technical characteristics:
1. Spectrum efficiency. As a result of high-performance modulator, channel coding, intertwined, and a balanced speech coding technology, the system has a high spectral efficiency.
2. Capacity. As the transmission bandwidth for each channel, so that the same frequency reuse requirements than the plant stem down to 9dB, it is the GSM system with frequency reuse can be reduced to 4 / 12 or 3 / 9 and even smaller (simulation system for the 7 / 21 ); Plus semi-rate voice coding and the introduction of the Automatic Call Distribution handoff to reduce the number of times, so that the capacity of the GSM system efficiency (per MHz per channel of the small number) than the TACS system, three to five times higher.
3. The quality of voice. In view of the characteristics of digital transmission technology, as well as norms relating to the GSM air interface and voice encoding definition in the threshold above, the voice quality is always achieve the same level of quality has nothing to do with wireless transmission.
4.'s Open interface. GSM standard provided by the open interface, is not limited to air interface, and the press, as well as direct Internet network devices between the entities, such as the A interface and Abis interface.
5. Security. Through authentication, encryption and the use of TMSI number to reach safety. Authentication to verify the user's right to access. Encryption for the air interface, by the SIM card and network of key decision AUC. TMSI is a business network to the user specified in the provisional identification number in order to prevent leakage and to track their location.
6. With ISDN, PSTN interconnection, and so on. Interconnection with other networks generally use of the existing interface, such as ISUP or TUP, and so on.
7. In the SIM card based on roaming. Roaming is an important feature of mobile communication, it marked the user can automatically from one network to another network. GSM system can provide global roaming, of course, need to network operators between certain agreements, such as billing.
GSM system has several important features: good ability to copy security, network capacity, resource-rich mobile phone number, the call clear, strong stability are less vulnerable to interference, and sensitive information, talk less dead, low-power mobile phones.
2.GSM technical characteristics:
1. Spectrum efficiency. As a result of high-performance modulator, channel coding, intertwined, and a balanced speech coding technology, the system has a high spectral efficiency.
2. Capacity. As the transmission bandwidth for each channel, so that the same frequency reuse requirements than the plant stem down to 9dB, it is the GSM system with frequency reuse can be reduced to 4 / 12 or 3 / 9 and even smaller (simulation system for the 7 / 21 ); Plus semi-rate voice coding and the introduction of the Automatic Call Distribution handoff to reduce the number of times, so that the capacity of the GSM system efficiency (per MHz per channel of the small number) than the TACS system, three to five times higher.
3. The quality of voice. In view of the characteristics of digital transmission technology, as well as norms relating to the GSM air interface and voice encoding definition in the threshold above, the voice quality is always achieve the same level of quality has nothing to do with wireless transmission.
4.'s Open interface. GSM standard provided by the open interface, is not limited to air interface, and the press, as well as direct Internet network devices between the entities, such as the A interface and Abis interface.
5. Security. Through authentication, encryption and the use of TMSI number to reach safety. Authentication to verify the user's right to access. Encryption for the air interface, by the SIM card and network of key decision AUC. TMSI is a business network to the user specified in the provisional identification number in order to prevent leakage and to track their location.
6. With ISDN, PSTN interconnection, and so on. Interconnection with other networks generally use of the existing interface, such as ISUP or TUP, and so on.
7. In the SIM card based on roaming. Roaming is an important feature of mobile communication, it marked the user can automatically from one network to another network. GSM system can provide global roaming, of course, need to network operators between certain agreements, such as billing.
GSM meaning
GSM full name: Global System for Mobile Communications, the world's Chinese mobile communication systems, commonly known as "GSM", originated in Europe is a mobile communication technology standard, is the second-generation mobile communication technology, and its purpose is to enable the development of the world Can be all over the joint use of a standard mobile phone network so that users will be able to use a phone line all over the world. China in the 20th century in the early 90's introduction of the use of technical standards, has been previously used analog cellular mobile technology, that is, the first generation of GSM technology (December 31, 2001 shut down our analog mobile network). At present, China Mobile, China Unicom each has a GSM network for the world's largest mobile communications network. GSM systems, including GSM 900:900 MHz, GSM1800: 1800MHz and GSM1900: 1900MHz band, and so on a few. GSM (Global System for Mobile Communications) is a widely used in Europe and other parts of the world's digital mobile phone system. GSM is used by the TDMA variant, and it is currently the number three wireless technologies (TDMA, GSM and CDMA) in one of the most widely used. GSM digital data, and data compression, and then with other users of the two data streams together from the channel sent the other two users have their own data flow slot. . In fact the European GSM standard of wireless phones, according to the GSM MoU reported that the Joint Commission, GSM in the world's 1.2 billion users, and more than 120 countries around the user. As many GSM network operators and other foreign operators have a roaming agreement, it is when the user to other countries, can continue to use their mobile phones.
Well-known U.S. telecommunications company Sprint an auxiliary branch in the United States is using GSM personal communications as a broadband personal communications services technology. This will be the ultimate personal communications services for Ericsson, Motorola, and Nokia's handset production is now set up more than 400 base stations. Handset, including telephone, walkie-talkie and pager messages.
GSM and other wireless technology is the evolution of mobile communications, mobile communications, including wireless high-speed circuit switched data, General Packet Radio System, based on the GSM network of enhanced mobile data communications technology as well as the Universal Mobile Telecommunications Service
Well-known U.S. telecommunications company Sprint an auxiliary branch in the United States is using GSM personal communications as a broadband personal communications services technology. This will be the ultimate personal communications services for Ericsson, Motorola, and Nokia's handset production is now set up more than 400 base stations. Handset, including telephone, walkie-talkie and pager messages.
GSM and other wireless technology is the evolution of mobile communications, mobile communications, including wireless high-speed circuit switched data, General Packet Radio System, based on the GSM network of enhanced mobile data communications technology as well as the Universal Mobile Telecommunications Service
GSM technical information
(1) .2 GSM system, technical specifications and its major properties
GSM standard norms of Chapter 12 Series: Series 01: The family of 02: 03 family business: network 04 Series: MS-BS and the Statute of the interface (air interface layer 2, 3) 05 Series: Wireless on the path to the physical Layer (the first air interface layer 1) 06 Series: voice coding norms Series 07: Taiwan's mobile terminal adapter 08 Series: BS to the MSC interface (A and Abis interface) Series 09: 10 interconnection Series: Series 11 available : Equipment and standardize the approval of the 12 series models: the operation and maintenance
(2) .3 GSM system, key technologies
The work of the band allocation
(2) -1. Band
China's public land-based digital cellular mobile communication networks using GSM communication system 900MHz band:
890 ~ 915 (Taiwan-made mobile, base station close)
935 ~ 960 (base-fat, Taiwan Mobile closed)
Duplex interval is 45MHz, for the work of the bandwidth 25 MHz, for the carrier frequency between 200 kHz.
With the development of the business, may need to extend down, or 1.8GHz frequency band to the GSM1800 transition, that is, the 1800MHz band:
1710 ~ 1785 (Taiwan-made mobile, base station close)
1805 ~ 1880 (base-fat, Taiwan Mobile closed)
Duplex interval is 95MHz, for the work of the bandwidth 75 MHz, for the carrier frequency between 200 kHz.
(2) -2. Channel spacing
Between the two adjacent channels to 200kHz. Each channel using Time Division Multiple Access (TDMA) mode, is divided into 8 slot, that is, 8-channel (full speed). Each channel bandwidth occupied by 200 kHz / 8 = 25 kHz.
GSM in the future semi-rate voice coding, each channel can accommodate 16 and a half rate channel.
(2) -3 Multiple Access Program
GSM communication systems used in multiple access technologies: Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA), coupled with frequency-hopping technology.
In the GSM wireless transmission paths on a basic concept: the transmission unit is about 100-bit modulation of the sequence, calling it a "sudden impulse." Pulse duration of the priorities in the wireless spectrum also accounts for a limited part. In the window of their time and frequency within the window to send, we call space. Accurately, the gap at the center of the system frequency band between 200 kHz arrangements (FDMA), which every 0.577ms (more precisely, is 15/26ms) once (TDMA). Corresponds to the same space of time as a slot, it will be the duration of time as a unit, known as BP (sudden pulse cycle).
Such a gap in time / frequency graph with a long 15/26ms, wide-200KHz said that the small rectangular (see Figure). Unity, the GSM will be provided for in a band called the 200KHz bandwidth gap.
(2) -4 at the time and frequency domain space
In the GSM system, each carrier frequency is defined as a TDMA frame, which is equivalent to a channel FDMA system. Each frame, including 8 time slot (TS0-7). Each TDMA frame, a TDMA frame.
TDMA frame, is 3 hours 28 minutes 53 seconds 760 ms (2048 * 51 * 26 * 8BP or 2048 * 51 * 26 TDMA frame) for the number of the cycle. * 51 * 2048 per 26 TDMA frame for a super-high frame, each frame can be divided into ultra-high 2048 super-frame, a super-frame is 51 * 26 TDMA frame of the sequence (6.12 seconds), each of the super-frame Conducted by the Multi-frame composition. Multi-frame is divided into two types.
26 frame of the complex: it includes 26 TDMA frame (26 * 8BP), continuing a long time 120ms. Such a complex of 51 frames to form a super-frame. This frame for the resumption of carry TCH (and SACCH increase FACCH).
51 frame of the complex: it includes 51 TDMA frame (51 * 8BP), continuing a long time 3060/13ms. Such a complex of 26 frames to form a super-frame. This frame for the resumption of BCH and carrying CCCH.
(2) -5 wireless interface management
In the GSM communications systems, wireless channel can be used far less than the number of potential users, two-way communication channel can only be allocated when needed. This is the standard telephone network is very different from the telephone network regardless of whether or not to call in each terminal are connected to a switch.
In the mobile network, users need to call and the release of dynamically allocated wireless channel. Whether the call issued by the mobile station, or sent to mobile call, the process requires the establishment of specialized methods used to make mobile access systems, in order to get a channel. In the GSM, is in the process of access to the exclusive use of a mobile station - base stations to achieve the channel. The channel for the transmission and paging information base stations - mobile channel, together known as GSM common channel, at the same time as it carried from / to many of the mobile station. On the contrary, in a certain period of time allocated to a separate channel of the mobile station known as a dedicated channel. As a result of this distinction, the definition of Taiwan's two mobile-hong state:
Idle mode: mobile radio listening in the channel, this time it did not take up any channel.
Specific models: a two-way channel of communication need to be allocated to the mobile station so that it can make use of peer-to-peer infrastructure, two-way communication.
Access so that the process of moving from Taiwan to the idle mode-specific model.
(3) 4GSM Channel
GSM channel in the channel is divided into physical and logical channel, a physical channel for a time slot (TS), which is based on the logical channel between MS and the BTS message and a different kind of a different definition of logical channel, the logical channel Mapped to the physical transmission channel. BTS from the MS known as the downlink direction, in the opposite direction as the uplink.
Logical channel is divided into two categories, business and the Channel Channel.
(3) -1. Business Channel (TCH):
After the code used to transmit voice or data customers in the uplink and downlink channel, point-to-point (BTS on a MS, or vice versa) to spread.
(3) -2. Channel:
Used to synchronize data transmission or signaling. According to the completion of the necessary functions of the Channel again defined as broadcasting, public and three specific Channel, which can be broken down into:
(3) -2-1. Security measures
GSM security system have been significantly improved, GSM and secrecy related to the functions of two goals: first, including to prevent unauthorized network access, (at the same time protect users from deceptive counterfeit); the second To protect the privacy of users.
To prevent unauthorized access through authentication (that is, insert the SIM card and mobile station provided by the user ID of the same security checks) to be achieved. From the operator side, which is the most important function, particularly in the case of international roaming, Internet access and control the user's record beyond its ability to pay.
To protect the privacy of users through different means, for transmission can be encrypted to prevent eavesdropping on communications in the wireless channel. Most of the signaling can also use the same method of protection against third parties who are called to understand. In addition, a temporary identification code to replace the user is unable to make the third-party tracking on GSM wireless users yet another mechanism.
(3)-2-2.PIN code
This is a simple method of authentication.
In the GSM system, customer information, such as signing were recorded in the SIM card. SIM card into a GSM terminal equipment, as will their telephone, call the billing records in the bill would name the SIM card. In order to prevent Daoda, billing errors have a bill in the SIM card PIN code set up operations (similar to the Password function on a computer). PIN code is from 4 to 8 digits, the median of its customers by its own decision. If a customer entered the wrong PIN code, it will give customers a prompt to re-enter if the 3rd consecutive input error, SIM cards have been closed, even if the SIM card will be pulled out or turn off the cell phone has no power required to operate To apply for by the operator to unlock the user.
(3) -2-3. Authentication
Authentication of the calculation as follows. RAND is one of the network side of the user's question, the only legitimate users will be able to give the correct answer SRES.
RAND is a network by the side of the AUC have a random number generator, a length of 128 bits, and its value at random from 0 to 2128-1 (tens of thousands of billion) within the framework of extraction.
SRES called to respond to symbols, the only user of the password parameter (Ki) of access to computing, 32-bit length.
Ki a very confidential way to store and the AUC in the SIM card, users do not understand their own Ki, Ki can be any length and format.
A3 algorithm for authentication algorithm, the decision by the operators, the algorithm is confidential. A3 algorithm is the only limit the length of the input parameters (RAND is a 128-bit) and the size of the output parameters (SRES must be 32-bit).
(3) -2-4. Encryption
In the GSM, transmission link in the encryption and decryption to deal with the location of all the special mode allows the data sent by a method of protection. Data is the customers can send information (voice, data, ... ...), and user-related signaling (such as the number being called to carry the news), even with the signaling systems (such as carrying ready to switch wireless measurements news) .
Encryption and decryption is a wireless emergency 114-bit pulse code with a special algorithm resulting 114-bit encryption or a different sequence for computing (A5 algorithm) completed. For each of the encrypted sequence of sudden, A5 enter the two calculations: the number of frames, and the other is a mobile station and the network agreed to between the key (called Kc), see figure. Uplink and downlink on the use of two different sequences: for every emergency, a series of mobile station for the encryption and decryption of the BTS as a sequence; sequence and the other for the BTS encryption, and as a Taiwan Mobile's decryption sequence.
(3) -2-4-1. Frame:
Frame coding, as a series of three values add up to a total of 22 bits.
For a variety of wireless channel, each frame of a sudden, all different, all in the same direction on a given emergency communications each using a different encryption sequence.
(3)-2-4-2.A5 algorithm
A5 algorithm must be within the framework of the international provisions of the algorithm can be described by the expertise of more than 22 parameters (frame number) and more than 64 special parameters (Kc) to generate more than 114 of the two long sequences of the black box.
(3) -2-4-3. Kc key
Prior to the beginning of encryption, key Kc must be mobile and the network agreed. GSM select the authentication key calculation during the Kc; key and then stored in the SIM card of the permanent memory. On the network side, the "potential" key to the store also called on the MSC / VLR, for the beginning of the use of encryption.
By the RAND (and for the same authentication) and Ki algorithm for calculating the Kc algorithm A8. A3 and the algorithm (by the RAND and Ki authentication algorithm for computing the SRES) similar to the decision by the operator of choice.
(3) -2-4-4. To protect the identity of users
The encryption of confidential information is very effective, but can not be used in the wireless path on the protection of each exchange of information. First of all, the public can not be used for encryption channel; Second, when the mobile station to a dedicated channel, the network did not know the identity of the user, can not be encrypted. Third parties may In both cases, the identity of the user to hear frame, so that the user's location at this time to roam. This is the user's privacy is harmful, GSM in order to ensure that the confidentiality of the introduction of a special function.
Where possible, through the use of temporary mobile user identity, TMSI alternative user IMSI, can be protected. TMSI by the MSC / VLR distribution, and we will continue to be replaced, the replacement cycle by the network operator set up.
GSM standard norms of Chapter 12 Series: Series 01: The family of 02: 03 family business: network 04 Series: MS-BS and the Statute of the interface (air interface layer 2, 3) 05 Series: Wireless on the path to the physical Layer (the first air interface layer 1) 06 Series: voice coding norms Series 07: Taiwan's mobile terminal adapter 08 Series: BS to the MSC interface (A and Abis interface) Series 09: 10 interconnection Series: Series 11 available : Equipment and standardize the approval of the 12 series models: the operation and maintenance
(2) .3 GSM system, key technologies
The work of the band allocation
(2) -1. Band
China's public land-based digital cellular mobile communication networks using GSM communication system 900MHz band:
890 ~ 915 (Taiwan-made mobile, base station close)
935 ~ 960 (base-fat, Taiwan Mobile closed)
Duplex interval is 45MHz, for the work of the bandwidth 25 MHz, for the carrier frequency between 200 kHz.
With the development of the business, may need to extend down, or 1.8GHz frequency band to the GSM1800 transition, that is, the 1800MHz band:
1710 ~ 1785 (Taiwan-made mobile, base station close)
1805 ~ 1880 (base-fat, Taiwan Mobile closed)
Duplex interval is 95MHz, for the work of the bandwidth 75 MHz, for the carrier frequency between 200 kHz.
(2) -2. Channel spacing
Between the two adjacent channels to 200kHz. Each channel using Time Division Multiple Access (TDMA) mode, is divided into 8 slot, that is, 8-channel (full speed). Each channel bandwidth occupied by 200 kHz / 8 = 25 kHz.
GSM in the future semi-rate voice coding, each channel can accommodate 16 and a half rate channel.
(2) -3 Multiple Access Program
GSM communication systems used in multiple access technologies: Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA), coupled with frequency-hopping technology.
In the GSM wireless transmission paths on a basic concept: the transmission unit is about 100-bit modulation of the sequence, calling it a "sudden impulse." Pulse duration of the priorities in the wireless spectrum also accounts for a limited part. In the window of their time and frequency within the window to send, we call space. Accurately, the gap at the center of the system frequency band between 200 kHz arrangements (FDMA), which every 0.577ms (more precisely, is 15/26ms) once (TDMA). Corresponds to the same space of time as a slot, it will be the duration of time as a unit, known as BP (sudden pulse cycle).
Such a gap in time / frequency graph with a long 15/26ms, wide-200KHz said that the small rectangular (see Figure). Unity, the GSM will be provided for in a band called the 200KHz bandwidth gap.
(2) -4 at the time and frequency domain space
In the GSM system, each carrier frequency is defined as a TDMA frame, which is equivalent to a channel FDMA system. Each frame, including 8 time slot (TS0-7). Each TDMA frame, a TDMA frame.
TDMA frame, is 3 hours 28 minutes 53 seconds 760 ms (2048 * 51 * 26 * 8BP or 2048 * 51 * 26 TDMA frame) for the number of the cycle. * 51 * 2048 per 26 TDMA frame for a super-high frame, each frame can be divided into ultra-high 2048 super-frame, a super-frame is 51 * 26 TDMA frame of the sequence (6.12 seconds), each of the super-frame Conducted by the Multi-frame composition. Multi-frame is divided into two types.
26 frame of the complex: it includes 26 TDMA frame (26 * 8BP), continuing a long time 120ms. Such a complex of 51 frames to form a super-frame. This frame for the resumption of carry TCH (and SACCH increase FACCH).
51 frame of the complex: it includes 51 TDMA frame (51 * 8BP), continuing a long time 3060/13ms. Such a complex of 26 frames to form a super-frame. This frame for the resumption of BCH and carrying CCCH.
(2) -5 wireless interface management
In the GSM communications systems, wireless channel can be used far less than the number of potential users, two-way communication channel can only be allocated when needed. This is the standard telephone network is very different from the telephone network regardless of whether or not to call in each terminal are connected to a switch.
In the mobile network, users need to call and the release of dynamically allocated wireless channel. Whether the call issued by the mobile station, or sent to mobile call, the process requires the establishment of specialized methods used to make mobile access systems, in order to get a channel. In the GSM, is in the process of access to the exclusive use of a mobile station - base stations to achieve the channel. The channel for the transmission and paging information base stations - mobile channel, together known as GSM common channel, at the same time as it carried from / to many of the mobile station. On the contrary, in a certain period of time allocated to a separate channel of the mobile station known as a dedicated channel. As a result of this distinction, the definition of Taiwan's two mobile-hong state:
Idle mode: mobile radio listening in the channel, this time it did not take up any channel.
Specific models: a two-way channel of communication need to be allocated to the mobile station so that it can make use of peer-to-peer infrastructure, two-way communication.
Access so that the process of moving from Taiwan to the idle mode-specific model.
(3) 4GSM Channel
GSM channel in the channel is divided into physical and logical channel, a physical channel for a time slot (TS), which is based on the logical channel between MS and the BTS message and a different kind of a different definition of logical channel, the logical channel Mapped to the physical transmission channel. BTS from the MS known as the downlink direction, in the opposite direction as the uplink.
Logical channel is divided into two categories, business and the Channel Channel.
(3) -1. Business Channel (TCH):
After the code used to transmit voice or data customers in the uplink and downlink channel, point-to-point (BTS on a MS, or vice versa) to spread.
(3) -2. Channel:
Used to synchronize data transmission or signaling. According to the completion of the necessary functions of the Channel again defined as broadcasting, public and three specific Channel, which can be broken down into:
(3) -2-1. Security measures
GSM security system have been significantly improved, GSM and secrecy related to the functions of two goals: first, including to prevent unauthorized network access, (at the same time protect users from deceptive counterfeit); the second To protect the privacy of users.
To prevent unauthorized access through authentication (that is, insert the SIM card and mobile station provided by the user ID of the same security checks) to be achieved. From the operator side, which is the most important function, particularly in the case of international roaming, Internet access and control the user's record beyond its ability to pay.
To protect the privacy of users through different means, for transmission can be encrypted to prevent eavesdropping on communications in the wireless channel. Most of the signaling can also use the same method of protection against third parties who are called to understand. In addition, a temporary identification code to replace the user is unable to make the third-party tracking on GSM wireless users yet another mechanism.
(3)-2-2.PIN code
This is a simple method of authentication.
In the GSM system, customer information, such as signing were recorded in the SIM card. SIM card into a GSM terminal equipment, as will their telephone, call the billing records in the bill would name the SIM card. In order to prevent Daoda, billing errors have a bill in the SIM card PIN code set up operations (similar to the Password function on a computer). PIN code is from 4 to 8 digits, the median of its customers by its own decision. If a customer entered the wrong PIN code, it will give customers a prompt to re-enter if the 3rd consecutive input error, SIM cards have been closed, even if the SIM card will be pulled out or turn off the cell phone has no power required to operate To apply for by the operator to unlock the user.
(3) -2-3. Authentication
Authentication of the calculation as follows. RAND is one of the network side of the user's question, the only legitimate users will be able to give the correct answer SRES.
RAND is a network by the side of the AUC have a random number generator, a length of 128 bits, and its value at random from 0 to 2128-1 (tens of thousands of billion) within the framework of extraction.
SRES called to respond to symbols, the only user of the password parameter (Ki) of access to computing, 32-bit length.
Ki a very confidential way to store and the AUC in the SIM card, users do not understand their own Ki, Ki can be any length and format.
A3 algorithm for authentication algorithm, the decision by the operators, the algorithm is confidential. A3 algorithm is the only limit the length of the input parameters (RAND is a 128-bit) and the size of the output parameters (SRES must be 32-bit).
(3) -2-4. Encryption
In the GSM, transmission link in the encryption and decryption to deal with the location of all the special mode allows the data sent by a method of protection. Data is the customers can send information (voice, data, ... ...), and user-related signaling (such as the number being called to carry the news), even with the signaling systems (such as carrying ready to switch wireless measurements news) .
Encryption and decryption is a wireless emergency 114-bit pulse code with a special algorithm resulting 114-bit encryption or a different sequence for computing (A5 algorithm) completed. For each of the encrypted sequence of sudden, A5 enter the two calculations: the number of frames, and the other is a mobile station and the network agreed to between the key (called Kc), see figure. Uplink and downlink on the use of two different sequences: for every emergency, a series of mobile station for the encryption and decryption of the BTS as a sequence; sequence and the other for the BTS encryption, and as a Taiwan Mobile's decryption sequence.
(3) -2-4-1. Frame:
Frame coding, as a series of three values add up to a total of 22 bits.
For a variety of wireless channel, each frame of a sudden, all different, all in the same direction on a given emergency communications each using a different encryption sequence.
(3)-2-4-2.A5 algorithm
A5 algorithm must be within the framework of the international provisions of the algorithm can be described by the expertise of more than 22 parameters (frame number) and more than 64 special parameters (Kc) to generate more than 114 of the two long sequences of the black box.
(3) -2-4-3. Kc key
Prior to the beginning of encryption, key Kc must be mobile and the network agreed. GSM select the authentication key calculation during the Kc; key and then stored in the SIM card of the permanent memory. On the network side, the "potential" key to the store also called on the MSC / VLR, for the beginning of the use of encryption.
By the RAND (and for the same authentication) and Ki algorithm for calculating the Kc algorithm A8. A3 and the algorithm (by the RAND and Ki authentication algorithm for computing the SRES) similar to the decision by the operator of choice.
(3) -2-4-4. To protect the identity of users
The encryption of confidential information is very effective, but can not be used in the wireless path on the protection of each exchange of information. First of all, the public can not be used for encryption channel; Second, when the mobile station to a dedicated channel, the network did not know the identity of the user, can not be encrypted. Third parties may In both cases, the identity of the user to hear frame, so that the user's location at this time to roam. This is the user's privacy is harmful, GSM in order to ensure that the confidentiality of the introduction of a special function.
Where possible, through the use of temporary mobile user identity, TMSI alternative user IMSI, can be protected. TMSI by the MSC / VLR distribution, and we will continue to be replaced, the replacement cycle by the network operator set up.
portable communication term
1, GSM
Used mobile phone users must be aware of what is meant by the representative of GSM, in fact, GSM is the Global System for Mobile Communications acronym, which means Global System for Mobile Communications, is the world's major cellular systems in the world. GSM is used for narrow-band TDMA, allows a radio frequency (that is, 'Cellular') at the same time 8-to-call group. It is based on European standards and to determine the frequency range between 900 ~ 1800MHz digital mobile telephone system, a frequency of 1800MHz system has been adopted by the United States. GSM was the beginning of 1991, the use of. By the end of 1997, has operations in more than 100 countries, Europe and Asia to become the de facto standard.
2, CDMA
CDMA and GSM, are also a mobile communication system, its full name in English is the Code Division Multiple Address (CDMA), which is based on the standards of the United States (IS-95) designed in the frequency range of 900 ~ 1800MHz Digital mobile telephone system. This is the adoption of a Spread-Spectrum's digital cellular technology. And the use of Time-Division Multiplexing (TDM) competitors (such as GSM) different, CDMA does not talk to each person to determine the allocation of a frequency, but allow each channel can be used to provide the full spectrum. CDMA calls for each group used to be a random sequence of numbers encoded.
3, Cellular
Cellular is a wireless communication technology. The technology to a geographical area is divided into several small areas, referred to as the "Cellular" (Cell), cellular technology be named. Phone (or cell phone) using this technology, often referred to as cellular phones (Cellular Phone). A large geographical area divided into a number of "Cellular" is designed to take full advantage of the limited radio frequency transmission. Each connection (for wireless phone conversations each group is concerned) will need a special frequency, and can use the frequency of a total of only about 1,000. In order to be able to more conversation at the same time, the cellular systems to each "cell" (that is, each small region) has been allocated a certain amount of frequency. Different cellular can use the same frequency, so that limited resources can be wireless full advantage of. Common cellular systems, including GSM and CDMA, they are second-generation communication technology.
4, CDPD
CDPD's full name in English is Cellular Digital Packet Data, which is dedicated to a cellular telephone data transmission technology. CDPD use of unused cellular channels (in between 800 to 900MHz), to transmit data packets. The technology provides for the transfer rate of 19.2Kbps, and through the use of analog cellular modem channel, connected to the time required for a shorter, stronger error correction. CDPD, but not the all-digital transmission of data, it is analog transmission and digital transmission between the transition. Compared with the all-digital, and its advantage is the use of existing analogue transmission infrastructure, relatively small investment. CDPD began in 1993, mainly for the United States, Canada, Mexico, as well as some in the Pacific Rim.
5, PCS
PCS is an acronym for Personal Communications Service, which means "personal communication services." This is the Federal Communications Commission (FCC) to use a term, the correction in the United States to deploy a set of digital cellular technology. PCS, including CDMA (also known as IS-95), GSM and for the North American TDMA (also called IS-136). The PCS frequency of 1900MHz.
6, TDMA
TDMA is Time Division Multiple Access acronym, with a Time-Division Multiplexing (Time Division Multiple Access) to provide digital wireless services, technology, it represents a kind of mobile phone systems, digital signal transmission technology. TDMA is divided into a number of radio slot, and then slot these sub-groups to call. In this way, a radio-frequency data can support multiple channels at the same time, the current technology has become today's D-AMPS and GSM systems.
7, GPRS
GPRS is General Packet Radio Service's acronym for "general packet radio service." This is a wireless communications standard, the speed of 150Kbps, the GSM than 15 times faster 9.6Kbps. GPRS can support a variety of bandwidth is limited and efficient use of bandwidth. This technology is particularly suitable for sending a small amount of data, such as send and receive E-mail, Internet browsing, can also be used for transmission of large amounts of data. It is the second-generation mobile communications technology transition to 3G, also known as the 25 people on behalf of communications technology.
8,3 G
3G is referred to as the Third Generation, is the third-generation mobile communications. The first generation of mobile communications is analog wireless network, the second generation is the widely used GSM and CDMA. 3G will have a broader bandwidth, the transmission speed of a minimum of 384Kbps, up to 2Mbps, not only voice transmission but also to transmit data to provide fast, convenient wireless applications, such as wireless access to Internet. 3G is still in its pilot phase, in 2002 is expected to be fully operational.
9, TACS
TACS is the full name in English Total Access Communications System, it is a system-wide communications network technology. The technology in accordance with British Standard designed analog mobile phone system, the frequency range of 900MHz.
10, Net Device
It literally means "network equipment" or "network device", but in reality it was not referring to the router or switch means, but with the realization of Internet networking equipment for small, does not include desktop and notebook computers. Net Device including handheld computers, two-way pager, set-top boxes, smart phones, car PC, as well as send and receive E-mail specialized small tools. It was also known as Net Device to Information Appliance (IA).
11, WCDMA
WCDMA is Wideband Code Division Multiple Access abbreviation. This is the third-generation wireless communication (3G) of a standard that can provide sufficient bandwidth to enable wireless multimedia applications possible.
12, DAMPS
DAMPS full name is the Digital AMPS, which is a high-AMPS mobile phone service technology for analog cellular systems, the use of 800MHz spectrum in the United States dominated. Correspond to, Digital AMPS is the representative of the digital advanced mobile phone system. This digital network solutions based on the IS-136 digital standard. 900 ~ 1800MHz spectrum in the implementation.
13, CMTS
CMTS on behalf of the Cellular Mobile Telephone System, is the meaning of the Chinese - cellular mobile telephone system. The system within each area covered by one base station. An area known as a cell. Each cell phone through the Department of base stations to achieve communication. If the Department of another cell phone call is automatically transferred to the new cell within the base station.
14, UMTS
UMTS represents Universal Mobile Telecommunications System, Chinese is the meaning of the Universal Mobile Telecommunications System, specifically the next generation of cellular technology. By the European Telecommunications Standards Institute to protect a group of companies currently developing its standards.
15, NMT450/NMT900
NMT is the Nordic Mobile Telephone System's initials, specifically the Nordic Mobile Telephone System technology. It is based on the Nordic standards established by the analog mobile phone system, the spectrum in the range of 450 and 900MHz.
16, PDC
PDC's full name in English is the Personal Digital Cellular, on behalf of the personal digital cellular phone. Japan in accordance with the standards established by the cellular mobile telephone system, the frequency range of 800 and 1500MHz.
Used mobile phone users must be aware of what is meant by the representative of GSM, in fact, GSM is the Global System for Mobile Communications acronym, which means Global System for Mobile Communications, is the world's major cellular systems in the world. GSM is used for narrow-band TDMA, allows a radio frequency (that is, 'Cellular') at the same time 8-to-call group. It is based on European standards and to determine the frequency range between 900 ~ 1800MHz digital mobile telephone system, a frequency of 1800MHz system has been adopted by the United States. GSM was the beginning of 1991, the use of. By the end of 1997, has operations in more than 100 countries, Europe and Asia to become the de facto standard.
2, CDMA
CDMA and GSM, are also a mobile communication system, its full name in English is the Code Division Multiple Address (CDMA), which is based on the standards of the United States (IS-95) designed in the frequency range of 900 ~ 1800MHz Digital mobile telephone system. This is the adoption of a Spread-Spectrum's digital cellular technology. And the use of Time-Division Multiplexing (TDM) competitors (such as GSM) different, CDMA does not talk to each person to determine the allocation of a frequency, but allow each channel can be used to provide the full spectrum. CDMA calls for each group used to be a random sequence of numbers encoded.
3, Cellular
Cellular is a wireless communication technology. The technology to a geographical area is divided into several small areas, referred to as the "Cellular" (Cell), cellular technology be named. Phone (or cell phone) using this technology, often referred to as cellular phones (Cellular Phone). A large geographical area divided into a number of "Cellular" is designed to take full advantage of the limited radio frequency transmission. Each connection (for wireless phone conversations each group is concerned) will need a special frequency, and can use the frequency of a total of only about 1,000. In order to be able to more conversation at the same time, the cellular systems to each "cell" (that is, each small region) has been allocated a certain amount of frequency. Different cellular can use the same frequency, so that limited resources can be wireless full advantage of. Common cellular systems, including GSM and CDMA, they are second-generation communication technology.
4, CDPD
CDPD's full name in English is Cellular Digital Packet Data, which is dedicated to a cellular telephone data transmission technology. CDPD use of unused cellular channels (in between 800 to 900MHz), to transmit data packets. The technology provides for the transfer rate of 19.2Kbps, and through the use of analog cellular modem channel, connected to the time required for a shorter, stronger error correction. CDPD, but not the all-digital transmission of data, it is analog transmission and digital transmission between the transition. Compared with the all-digital, and its advantage is the use of existing analogue transmission infrastructure, relatively small investment. CDPD began in 1993, mainly for the United States, Canada, Mexico, as well as some in the Pacific Rim.
5, PCS
PCS is an acronym for Personal Communications Service, which means "personal communication services." This is the Federal Communications Commission (FCC) to use a term, the correction in the United States to deploy a set of digital cellular technology. PCS, including CDMA (also known as IS-95), GSM and for the North American TDMA (also called IS-136). The PCS frequency of 1900MHz.
6, TDMA
TDMA is Time Division Multiple Access acronym, with a Time-Division Multiplexing (Time Division Multiple Access) to provide digital wireless services, technology, it represents a kind of mobile phone systems, digital signal transmission technology. TDMA is divided into a number of radio slot, and then slot these sub-groups to call. In this way, a radio-frequency data can support multiple channels at the same time, the current technology has become today's D-AMPS and GSM systems.
7, GPRS
GPRS is General Packet Radio Service's acronym for "general packet radio service." This is a wireless communications standard, the speed of 150Kbps, the GSM than 15 times faster 9.6Kbps. GPRS can support a variety of bandwidth is limited and efficient use of bandwidth. This technology is particularly suitable for sending a small amount of data, such as send and receive E-mail, Internet browsing, can also be used for transmission of large amounts of data. It is the second-generation mobile communications technology transition to 3G, also known as the 25 people on behalf of communications technology.
8,3 G
3G is referred to as the Third Generation, is the third-generation mobile communications. The first generation of mobile communications is analog wireless network, the second generation is the widely used GSM and CDMA. 3G will have a broader bandwidth, the transmission speed of a minimum of 384Kbps, up to 2Mbps, not only voice transmission but also to transmit data to provide fast, convenient wireless applications, such as wireless access to Internet. 3G is still in its pilot phase, in 2002 is expected to be fully operational.
9, TACS
TACS is the full name in English Total Access Communications System, it is a system-wide communications network technology. The technology in accordance with British Standard designed analog mobile phone system, the frequency range of 900MHz.
10, Net Device
It literally means "network equipment" or "network device", but in reality it was not referring to the router or switch means, but with the realization of Internet networking equipment for small, does not include desktop and notebook computers. Net Device including handheld computers, two-way pager, set-top boxes, smart phones, car PC, as well as send and receive E-mail specialized small tools. It was also known as Net Device to Information Appliance (IA).
11, WCDMA
WCDMA is Wideband Code Division Multiple Access abbreviation. This is the third-generation wireless communication (3G) of a standard that can provide sufficient bandwidth to enable wireless multimedia applications possible.
12, DAMPS
DAMPS full name is the Digital AMPS, which is a high-AMPS mobile phone service technology for analog cellular systems, the use of 800MHz spectrum in the United States dominated. Correspond to, Digital AMPS is the representative of the digital advanced mobile phone system. This digital network solutions based on the IS-136 digital standard. 900 ~ 1800MHz spectrum in the implementation.
13, CMTS
CMTS on behalf of the Cellular Mobile Telephone System, is the meaning of the Chinese - cellular mobile telephone system. The system within each area covered by one base station. An area known as a cell. Each cell phone through the Department of base stations to achieve communication. If the Department of another cell phone call is automatically transferred to the new cell within the base station.
14, UMTS
UMTS represents Universal Mobile Telecommunications System, Chinese is the meaning of the Universal Mobile Telecommunications System, specifically the next generation of cellular technology. By the European Telecommunications Standards Institute to protect a group of companies currently developing its standards.
15, NMT450/NMT900
NMT is the Nordic Mobile Telephone System's initials, specifically the Nordic Mobile Telephone System technology. It is based on the Nordic standards established by the analog mobile phone system, the spectrum in the range of 450 and 900MHz.
16, PDC
PDC's full name in English is the Personal Digital Cellular, on behalf of the personal digital cellular phone. Japan in accordance with the standards established by the cellular mobile telephone system, the frequency range of 800 and 1500MHz.
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