he two dominant standards for PCS networks: TDMA (time-division multiple access) and CDMA (code-division multiple access). Most existing TDMA is based on the PCS-1900 architecture of GSM (global system for mobile technology), the European digital cellular phone standard used by about 150 wireless providers in 86 countries (Glossary, 1995). The basic GSM architecture is shown in Exhibit 1.
TDMA uses exclusive narrowband frequency channels, subdivided into time slots. TDMA is a method of digital wireless transmission, allowing many users to access, in sequence, a single radio frequency channel without interference by allocating unique time slots to each user within each channel (see Exhibit 2). Time Division Multiple Access (TDMA) is a method of utilizing radio spectrum. It provides each user access to the entire frequency channel for a brief period, during which the user transmits data. For example, each channel may be shared by four users by assigning time slots to each user and transmitting pieces of each voice or data transmission via synchronized timed bursts (Glossary, 1995).
CDMA technology was developed in 1989 by researchers in the US after European adoption of GSM and US approval of TDMA as a standard. CDMA transmits all messages at the same time and the same frequency and spreads them across the spectrum with pseudorandom noise, creating a wide-bandwidth signal that is unscrambled at the receiver base station (CDMA, 1995).
CDMA is a method of digital wireless transmission allowing a large number of users to simultaneously access a single radio frequency channel by allocating unique code sequences to each user across each channel. CDMA is a spread spectru
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