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Unformatted text preview: three communications simultaneously. This technology is
primarily used in the US.
2. GSM. Global System for Mobile (GSM) communications technology is also
based on time-division multiplexing of each cellular channel. However, it uses
wider carrier frequencies than TDMA are divides each cellular channel into eight
time slots, rather than three.
Hence, GSM technology can handle eight
communications simultaneously. This technology is primarily used in Europe and
3. CDMA. Code-Division-Multiple-Access (CDMA) technology does not divide
a channel into sub-channels, like TDMA or GSM. Instead, it carries multiple
transmissions simultaneously by filling the entire communications channel with
data packets coded for various receiving devices. The packets go only to the
devices for which they are coded. This technology is primarily used in the US.
As upgrades to 2G technologies, 2.5G technologies were developed to provide
more bandwidth for higher data transfer rates. 2.5G uses High-Speed-CircuitSwjtched-Data (HSCSD) technology, which is basically an extension of GSM
technology that can offer throughput of up to 384 Kbps. Although 2.5G offers
more bandwidth than 2G, it is less than that offered by 3G. However, since 2.5G
uses existing 2G spectra and does not require: entirely new network infrastructure,
it can be implemented faster and less expensively than 3G. 2.5G comprises of the
following three primary standards:
1. iDEN. Integrated Digital Enhanced Network (iDEN) is a GSM upgrade that
uses enhanced compression and modulation technologies to deliver data transfer
rates of 64 Kbps. It is primarily used in North America, South America, China,
and Japan. 2. GPRS. General Packet Radio Service (GPRS) is another GSM upgrade that
offers data transfer rates of up to 171 Kbps. It can thus be used for applications
such as videoconferencing and interacting with multimedia web sites. GPRS
reallocates several GSM time slots for voice to data uses, thereby increasing data
rates but decreasing voice rates. It...
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This document was uploaded on 04/07/2014.
- Spring '14