A multiuser chip-rate equalization algorithm for CDMA underwater communication systems

In this paper, direct-sequence code-division multiple-access (CDMA) is considered for multiuser communication network in underwater acoustic channel, where extended multipath and rapid time-variability is encountered. To track and compensate the channel distortion, a decentralized hypothesis-feedback equalization (HFE) algorithm which updates coefficients at chip rate is a promising method and has been used (M. Stojanovic, et al., 2000). But due to multiple access interference (MAI), its performance suffers degradation. For this reason, successive interference cancellation hypothesis-feedback equalization (SIC-HFE) algorithm is proposed, which combines the capabilities of HFE to track the time-varying channel and SIC implemented by cross-over feedback filters to cancel out the MAI effects between users. Simulation results proved that the proposed algorithm could significantly improve the performance of asynchronous multiuser CDMA underwater communication system.