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Joined: Dec 2008
21-09-2008, 11:18 AM
Cellular mobile radio systems aim to provide high-mobility, wide-ranging, two-way wireless voice communications. These systems accomplish their task by integrating wireless access with large-scale networks, capable of managing mobile users. Cellular radio technology generally uses transmitter power at a level around 100 times that used by a cordless telephone (approximately 2 W for cellular).
Cellular radio has evolved into digital radio technologies, using the systems standards of GSM (at 900 and 1800 MHz) in Europe, PDC in Japan, and IS-136A and IS-95A in the United States. Third-generation systems, such as wideband code division multiple access (WCDMA) and cdma2000, are currently under development.
One of the most significant consideration in designing digital systems is the high cost of cell sites. This has motivated system designers to try to maximize the number of users per megahertz, and users per cell site.
Another important consideration is maintaining adequate coverage in areas of varying terrain and population density. For example, in order to cover sparsely populated regions, system designers have retained the high-power transmission requirement to provide maximum range from antenna locations.
Communications engineers have also been developing very small coverage areas, or microcells. Microcells provide increased capacity in areas of high user density, as well as improved coverage of shadowed areas. Some microcell base stations are installed in places of high user concentrations, such as conference center lobbie
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