A Walsh code assignment scheme for minimizing CCDF of RF envelope power in forward link signal of the CDMA base station

The forward link signal in IS-95 CDMA base station is comprised of multiple orthogonal Walsh codes separating each traffic channel. The composite signal is essentially a noise-like signal with very high Peak-To-Average power ratio (PAR) and quite severe Complementary Cumulative Distribution Function (CCDF). Such signals burden the final stage power amplifier in the BTS and introduce signal clipping. The signal clipping further results in out of band emissions raising the ACPR of the signal beyond regulatory standards.; This research studies the factors that cause the high PAR and severe CCDF in the CDMA signal and then proposes a scheme by use of which the PAR of the composite signal can be kept at minimum as characterized by the less severe CCDF, thus reducing clipping and hence improving ACPR.; We further extend the research to identify the factors that impact PAR of the signal in W-CDMA systems. We suggest few guidelines that if followed, would result in W-CDMA signal with minimum PAR at any time.; By means of simulation and actual experimentation in the lab, we measure the performance of the proposed scheme.