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quote:Originally posted by j_mchattieIsnt it more about frequency though?And what to mobile phones give out (mw?)
quote:BackgroundContemporary 'digital' mobile phones in Europe operate using the GSM (Global Systems Mobile) system. There are two frequency bands allocated to GSM mobile phones, one at 900MHz, and one at 1800MHz. GSM uses a combination of frequency division multiple access (FDMA) and time division multiple access (TDMA). What this means in reality is that within each band there are a hundred or so available carrier frequencies on 200kHz spacing (the FDMA bit), and each carrier is broken up into time-slots so as to support 8 separate conversations (the TDMA bit). Correspondingly, the handset transmission is pulsed with a duty cycle of 1:8; and the average power is one eighth of the peak power. Once a call is in progress, the phones are designed to reduce the radiofrequency (RF) output power to the minimum required for reliable communication - under optimum conditions, the power can be set as low as 20mW (one hundredth of full power). Battery consumption and radiation output of the handset is further reduced by using 'discontinuous transmission' (DTX); the phone transmits very much less data during pauses in the conversation. Code: [Select] Base station transmit Handset transmit Peak handset power used in the UK primarily byGSM900 935-960MHz 890-915MHz 2 watts BT Cellnet and VodafoneGSM1800 (PCN) 1805-1880MHz 1710-1785MHz 1 watt Orange and One2oneThe basic handset transmission consists of carrier bursts of 0.577ms duration, repeating every 4.615ms, giving a repetition rate of 216.7Hz. The data is encoded using a phase modulation scheme known as 'Gaussian Minimum Shift Keying' (GMSK) and a symbol duration of about 4µs, which doesn't affect the carrier amplitude. Owing to the coding and control protocols, every 26th pulse is omitted during a conversation, leading to a component in the output modulation at 8.33Hertz.
Base station transmit Handset transmit Peak handset power used in the UK primarily byGSM900 935-960MHz 890-915MHz 2 watts BT Cellnet and VodafoneGSM1800 (PCN) 1805-1880MHz 1710-1785MHz 1 watt Orange and One2one