CHAPTER 14 CDMA Wireless Communications The term CDMA stands for Code Division Multiple Access. CDMA modulation and demodulation technology grew out of military spread spectrum techniques. CDMA technology was commercialized by Qualcomm in the early 1990s. The initial Qualcomm CDMA system was known as IS-95. Later, Qualcomm developed and deployed an enhanced version of IS-95, known as CDMA2000 1xRTT, or just CDMA2000. 14.1 Spread Spectrum Technology The basic idea behind spread spectrum is to start with a narrow band signal and mix it with a high-frequency pseudo-random number (PN) signal, which would have the effect of "spreading" the frequency spectrum occupied by the signal, thereby making it much harder for adversaries to jam or interfere (see Figure 14.1). Upon reception, the process could be reversed using the same pseudo-random code, and the original signal recovered.