Influence of various PN sequence phase optimization criteria on the SNR performance of an asynchronous DS-CDMA system

The AO/LSE, LSE/AO and MSE/AO spreading code phase optimization criteria are compared with each other and with the minimum mean-square cross-correlation cross-optimal (MSQCC/CO) and CO/MSQCC criteria. 13 sets of code of lengths 31-511 are used as examples. It is concluded that a criterion of any kind does not give any advantage unless E/sub b//N/sub 0/ is >10 dB. The optimization also loses its importance when the code length is /spl ges/255. It is also found that the AO/LSE, LSE/AO and MSE/AO criteria cannot be put into the order of quality from the viewpoint of reduced multiple-access interference. In addition, the MSQCC/CO criterion results in the best SNR performance. The CO/MSQCCC criterion is second best. It is also recommended to use the MSQCC/CO criterion instead of, for example, the AO/LSE criterion, as a sieve to choose PN sequences for the purpose of numerical analysis of bit error probability of an asynchronous CDMA system to obtain the best results and to avoid uncertainty.