Partial Multiuser Detection for CS-CDMA/CP over Multipath Channels and Its Comparison with DS-CDMA

Convolutional spreading CDMA with cyclic prefix (CS-CDMA/CP) enables multiuser interference-free (MUI-free) transmission over multipath downlink channels with the use of zero correlation zone (ZCZ) codes. However, MUI-free transmission is guaranteed only when the data length D, channel delay L, and ZCZ length Z satisfy Z + 1 ges D + L, and the user population is constraint to be K les [N/(Z+1)], where N is the code length. In this paper, for the purpose of allowing higher bandwidth efficiency for more active users, we propose an iterative partial multiuser detector for CS-CDMA/CP with M-ZCZ code to allow Z + 1 < D + L. Because the detector is implemented in the symbol-level (after despreading) and only a partion of users are jointly considered, its receiver complexity is expected to be acceptable for a mobile terminal. Comparison with the DS-CDMA system employing chip-equalization receiver shows that the CS-CDMA/CP system employing the proposed receiver offers a better tradeoff between the performance and receiver complexity, which indicates its potential application in future wireless communications.