BASICS OF MOBILE CELLULAR COMMUNICATIONS

From the subscribers point of view, mobile systems are perhaps the most exciting telecommunications development since the invention of the telephone. The developments

Of optical fiber technology sound very impressive and the statistics involved is mind boggling to the average person in the street, but that person does not usually fully appreciate how he or she benefits personally. Such developments are mainly occurring

In the wings or backstage and are not really tangible service improvements to the

Subscriber. In the fact, good service is expected.

The pocket telephone, on the other hand, is a revolution that is center stage and whose

Benefits can be instantly appreciated by a person who decided to invest in one of these

Devices. However, despite the many advantages of being in contact with business associates or friends at all hours of the day, no matter where one many happen to be

Within a city, there are some sociological disadvantages to the pocket telephone.

For example, the anti social aspects of receiving calls in a quiet restaurant have already

Prompted some establishments to require customers to leave their pocket phones at the
Reception desk.

Cellular mobile telephone systems are difficult to classify. They could be considered

To be part of the local loop since they extend out to the subscriber handset. Because of the distances traveled between a fixed subscriber and the mobile subscriber (or mobile-to-mobile subscriber), they could be called long-haul circuits. The technology incorporated some of the most advanced radio transmission techniques. In addition, the call processing

Requires high-level digital switching techniques to locate the mobile subscriber and setup and to maintain calls while the mobile subscriber and setup and to maintain calls

While the mobile subscriber and setup and to maintain calls while the mobile subscriber is in transit.

The portable telephone was only recently made possible by the miniaturization resulting from VLSI electronic circuitry. Even today there are still some technologies problems to solve, such as increasing the time between recharging the batteries of portable telephones. More serious is the fact that vehicular mobile telephones and portable radiotelephones have some severe technical incompatibilities. These take

Two forms. First, the systems developed in different parts of the world do not yet

Even have the same operating frequency,and the system designs vary quite considerably. However ,the ITU is currently coordinating Recommendations with all

Major parties to enable equipment compatibility fo r the next generation of cellular mobile radio systems. Second,one can say there are three generations of cellular radio

Systems: analog FM, narrowband TDMA,and wideband CDMA. The analog has been around for a number of years, narrowband TDMA is currently being put into service,

And wideband CDMA is possibly on the horizon. There are significant equipment incom

Patibilities when moving from one system to the other or trying to incorporate two or three of thses into the same network.Many of these problems stem from the difference

In power outputs. Vehicle radios transmit at relatively high power levels in the region of 1 of 10 W,whereas portable units transmit relatively low power levels of 1 to 10mW. While this is fine for the customer, it makes coexistence of the two systems a network

Planners nightmare.

In summary, cellular telephony is the culmination of several technologies which have progressed in parallel over the past two decades.In fact,the progress has been so

Rapid that the ITU has had a problem in organizing CCITT/CCIR meetings fast enough

To determine standards that are consistent with the new technology.