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| GSM |
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The original meaning of GSM was Group Special Mobile, however, it has changed to Global System for Mobile Communications. GSM is a standard digital cellular phone service used worldwide. Although there are several such standards, GSM has become increasingly popular in most countries and is gaining ground in the US also. What GSM does is determine standards for the infrastructure of a digital service. Subscriber data is carried on a SIM, or "smartcard", which is inserted into the cell phone to make it operative. This allows the subscriber to opt for either SIM card mobility or terminal mobility through different networks.Worldwide, four frequencies are used: 450 MHz, 900 MHz, 1800 MHz, and 1900 MHz GSM Technology: Access Method: mixed TDMA & FDMA Security: Optional radio interface encryption Carrier frequency division: 200 KHz Users per carrier frequency: 8 Transfer rate: 13 kbps (speech bit rate) or half rate Total bit rate: 21 kbps Bandwidth per channel: 25 KHz
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The World of Communications
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