Compared to the old wireless analog technologies, digital wireless technologies offer many extra features like data and text messages and notably enhanced sound quality. This is possible because the signal as digital bits can be manipulated in a way that adds capacity to the network system, increases call clarity, and allows the use of digital protocols.

Despite the name, however, the Personal Communications System-PCS-isn't just one system, but a number of systems.

GSM

Developed by the European Telecommunications Standards Institute, the Global System for Mobile Communications has been used commercially since 1991. It serves close to 30 million subscribers in about 100 countries, or almost one third of the total world market for wireless telecommunications. GSM is the fastest growing wireless phone technology in the world, expected to reach more than 100 million users by the year 2000-and eventually, half the market for mobile phones. Supported by more than 200 network service providers, GSM networks already cover more than 2.7 billion people in Europe, Africa, Australia, New Zealand, China, India, and other parts of Asia, the Middle East, and North America.

Each GSM phone has a removable Smart Card, also known as Subscriber Identification Module (SIM) roughly the size of a credit card or a micro chip. The card is used for storing phone numbers, your PIN code, billing information, and subscriber identity.

In Europe, GSM usually refers to digital cellular networks that use the 900 MHz frequency band. Since these networks have suffered from congestion, a new upbanded version was created in 1993 called Digital Communications System 1800 (DCS). DCS can use the same features as 900 MHz GSM but it operates in the 1700-1800 MHz range.

In North America, GSM is also known as PCS-1900, using the 1850-1990 MHz band.

TDMA

Time Division Multiple Access, using the 800 MHz frequency range, was the first digital technology to be used in the U.S. by cellular systems. Transmission, however, also included echoes and other distortions. The recently established PCS version is called IS-136 TDMA. Network service providers can use this standard to migrate their networks from analog to digital operation, thereby increasing capacity.

By the year 2000, TDMA is expected to support 24 million users, 19 million of them in the U.S.

CDMA

The PCS Code Division Multiple Access system was not released commercially until 1996. CDMA has only about 250,000 users worldwide, expected to grow to 32 million in three years.

The major difference between GSM and CDMA is in how CDMA adds capacity to a wireless network. Instead of dividing calls up by time like GSM and TDMA, CDMA assigns each call a unique code. CDMA thus has the highest network capacity of any wireless technology.

For more information on digital wireless technologies, check out these Web sites: Cell Talk (http://www.celltalk.com), GSM World (http://www.gsmworld.com), The Personal Communications Industry Association (http://www.pcia.com), and The World of Wireless Communications (http://www.wow-com.com/consumer).