The Code Division Multiple Access (CDMA) technology was developed by Qualcomm, and has been operating in the United States since 1996. CDMA allows many users to share a common frequency/time channel for transmission. The user signals are distinguished by spreading them with different codes. In theory, this technology optimizes the utilization of the frequency bandwidth by equalizing signal-to-noise ratio (SNR) among all the users, thereby more equitably sharing the system power resources among them. While AMPS users who are near base stations typically enjoy SNRs (Signal to Noise Ratios) excess of 80dB. Users at the edge of cell coverage areas experience SNRs near the lower limit. With CDMA, users who are near base stations transmit less power maintaining the same SNR as users at the edge of a cells coverage.
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