Business Data Communications and Networking

Appendix D. CELLULAR TECHNOLOGIES

Cellular technology is becoming increasingly popular. Its most common use is to provide cellular telephone services, but the cellular network is also being used more and more often by data communication devices such as pagers, personal digital assistants (PDAs), and handheld computers.

Cellular technology is a form of high frequency radio in which antennas are spaced strategically throughout a service area. The service area is divided into many cells, each with its own antenna. This arrangement generally provides subscribers with reliable mobile telephone service of a quality almost that of a hardwired telephone system. Users (voice or data transmission) dial or login to the system, and their voices or data are transmitted directly from their telephone to one of these antennas. In this way, the cellular system replaces the hardwired local loop. Each phone service provider uses a different part of the radio frequency spectrum, which is why cell phones designed for one provider's network often won't work on another provider's network.

This network of cell antennas is an intelligent system. For example, as you drive your car through the service area, you move away from one antenna and closer to another. As the signal weakens at the first antenna, the system automatically begins picking up your signal at the second antenna. Transmission is switched automatically to the closest antenna without communication being lost.

The current technology used for cell ...