Model of silence reallocation in a code division multiple access system

There has been an increased demand for digital cellular communications, especially in large cities where the existing cellular networks have become saturated. However, the growing demand has not been accompanied by an increase in the available spectrum which would allow use of existing technology. Furthermore, there should be an even greater demand in the future due to expected growth in the number of users. There is a limited amount of RF spectrum that has been allocated by the FCC to cellular communications (800-900 MHz and 1.8-2.0 GHz). To increase the capacity, the only alternatives available, in lieu of increasing available RF spectrum, are to invent new technology or to more efficiently use the currently available technology. The Telecommunication Industry Association (TIA) has standardized CDMA as the TIA Interim Standard 95 (IS-95). The IS-95 systems can carry about 10-15 times as many voice calls as an analog system in the same spectrum. It is well known that voice communications consists of both talkspurts and silent periods. Talkspurts consist of only 40 percent of the call, the remaining 60 percent of the call is silence. The authors are studying the reallocation of silent periods to a lower grade of data users in an attempt to integrate voice and data users in a CDMA system and to maximize use of the available RF spectrum