Wlan And Other Wireless Technologies

The key technologies for wide-coverage voice and data applications are cellular networks. Currently, second generation (GSM, CDMAone, TDMA and PDC/PHS) represents more than 98% of the mobile marker. GSM and GPRS (General Packet Radio Service), offers around 40 kbps. An improved version called EDGE (Enhanced Fata Rate for Global Evolution) triples the GPRS bit rate capacity. CDMAOne (IS-95B) allows data rates of up to 64 kbps.

Third-generation cellular technology will enhance the user experience thanks to significantly increased bit rate capacity. UMTS (Universal Mobile Telecommunication System) offers data rates of up to 384 kbps. HSDPA (High Speed Downlink Packet Access) has increased UMTS data rates up to five times. CDMA200 1XRTT, a simple evolution of CDMAOne, supports packet data service up to 144 kpbs. CDMA2000 1xEV-DO, which is reserved for data, offers throughput of over 700 kbps. In the future it is planned that CDMA2000 1XEV-DV, like UMTS, integrate voice and high-speed data on the same frequency band.

For indoor voice applications, DECT (Digital Enhanced Cordless Telecommunications) has been around in the enterprise environment for more than 10 years. Residential applications such as the cordless telephone has driven the cost of materials for DECT products down very low, but its long-term future is uncertain owing to the availability of voice-over-WLAN handsets that reuse the WLAN infrastructure deployed for data. WLAN can also complement cellular technologies in public WLAN ''hot spots.'' Public WLAN offers high data rates (several Mbps) in any of the 50,000 hot spots that currently exist in places such as airports, hotels or conference centers. Nevertheless, WLAN, while offering clear benefits, is limited in its coverage and mobility capabilities for public applications.

Worldwide Inoperability for Microwave Access, (WIMAX) in particular with the IEEE 802.16e variant, overcomes these limitations and can offer broadband connectivity in extended areas (''hot zones''). Thanks to state of the art radio technology, WIMAX offers broadband wireless access at data rates of several tens of Mbps and over a range of several tens of kilometers. Another technology, Mobile-Fi, (IEEE 802.20) can cope with terminals moving up to 250 km/h but at the price of limited bit rate capacity making the future of this technology uncertain.

For short-range connectivity, Bluetooth (IEEE 802.15.1), allows the suppression of cumbersome cable connections for Personal Area Networks (PAN). However, Bluetooth is complemented by the low data rate, Zigbee (IEEE 802.15.4), for specific application, thanks to very efficient power consumption and very low cost. On the other hand, ultrawideband (uWb) is aimed at short range, very high data-rate applications, but the standard IEEE 802.15.3 is still far from being finalized. The first UWB application may be to replace current USB cables, and then possibly home networking applications to replace or complement residential WLAN.

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