Selection diversity reception of spread-spectrum signals with unequal mean strengths

An analytical framework to evaluate the performance of two different selection diversity schemes in various mobile radio environments is developed. The average bit-error rate analysis applies to phase-coded spread-spectrum systems, over a Nakagami multipath fading channel. In this study, we take into account of the variations in the mean signal and noise power levels on each of the independent diversity branches. This is an important consideration because in practice equal mean signal strengths are rarely available, which will result in certain loss of diversity gain. Our results indicate that S+I selection model outperforms the traditional SNIR selection scheme if the discrepancy between the mean signal strengths are small, owing to the statistical nature of the multiple access interference. DS-CDMA systems are discussed in particular