Code Division Multiple Access

Spread spectrum systems were originally developed for military applications, to provide antijam and low probability of intercept communications by spreading a signal over a large frequency band and transmitting it with a low power per unit bandwidth [73], [247], [286]. Recently, code division multiple access (CDMA) based on spread spectrum technology has been recognized as a viable alternative to both frequency division multiple access (FDMA) and time division multiple access (TDMA) for cellular systems. During the late 1980s and early 1990s, Qualcomm, Inc.’s efforts, along with those of many other organizations such as Motorola and AT&T, have lead to the North American IS-95 cellular standard [79]. A detailed description of the IS-95 CDMA cellular approach can be found in a number of papers, including those by Lee [181] and Gilhousen et al. [118]. The book by Viterbi [324] provides a good coverage of the spread spectrum concepts that form the foundation of the IS-95 CDMA cellular system.