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dddThe cellular industry is dominated by two technologies - Global System for Mobile Communication (GSM) and Code Division Multiple Access (CDMA). This note gives an overview of the two different technologies. The note starts with the history of GSM and goes on to describe the GSM architecture and the GSM family. It also provides information on the services provided by GSM and the working of GSM. The note also takes a look at the history of CDMA and its commercial development. It then does a comparative study of the two technologies and discusses their advantages and disadvantages.

INTRODUCTION INTRODUCTION
The world's first cellular networks introduced in the early 1990s, used analog2 radio transmission technologies. Within a few years, millions of subscribers signed up for service provided by the cellular networks, and demanded more and more airtime3. As a result, dropped calls and network busy signals became common in many areas.
To accommodate more calls within the limited amount of radio spectrum4 available, the industry developed a digital5 wireless technology called GSM (Global System for Mobile Communication). Today, most of the cellular phones in the world, outside the U.S., use GSM technology. GSM, one of the oldest technologies used by the cellular industry, is considered to be very dependable technology. By the beginning of the 21st century, one billion cellular phones used this technology.GSM has always grown and adapted to the changing needs of customers. The number of GSM subscribers has increased over the years, with around 160 million new customers added in 2002 alone. From 1997 to 2003, the number of GSM customers increased 10 times. GSM, which is continuously evolving at a rapid pace, provides several voice and data enabled services.

But just as GSM was being standardized, an even better solution for mobile communication6 was found in another technology called CDMA (Code Division Multiple Access). CDMA, a digital wireless technology,...