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"!