Mobile phone use and cancer

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Abstract
After not more than 20 years of mobile telecommunication, the third generation of mobile phones is already awaiting introduction onto the market (some test areas are now in operation). In Europe mobile telephony started in 1981, and in the USA in 1983. The first generation mobile phones were the so called analogue types. The signal was transmitted by frequency modulation in frequency bands around 450 MHz and 900 MHz. The mobile phones had peak power of emission of about 8–15 W for the 450 MHz system and of about 1 W for the 900 MHz telephony. In the early 1990s second generation mobile phone systems were started in several European countries. This system was a digital one that used frequency bands around 900 MHz (GSM) and later 1800 MHz (DCS). This technology made compression of speech possible and therefore transmission to and from several mobile phones using the same channel could be applied. This type of transmission is called TDMA. Up to eight mobile phones can use the same channel for transmission. Each is given a time slot of 577 µs (hence the term TDMA: time division multiple access). Within this time slot a signal of analogue duration of 4.615 ms (called a frame) is transmitted by a microwave pulse (bit coding of the digital information is accomplished by GMSK). Hence the basic pulse frequency is 217 Hz. Furthermore, the system applies power regulation to adjust output to the quality of the signal received and it is capable of discontinuous transmission (DTX mode), thereby reducing the number of pulses emitted from the mobile phone if the user is silent. Peak power output of the mobile phone antenna is 2 W (900 MHz) and 1 W (1800 MHz). Different TDMA systems operate in the USA, Japan, and other countries. Digital cordless phones apply a similar technology, and despite considerably lower power may result in average exposures comparable to GSM mobile phones.