Reduced complexity multiuser receivers for asynchronous trellis coded DS-CDMA systems

Previous works have shown that multiuser receivers with trellis-coded modulation significantly improve performance in CDMA transmissions over bandwidth limited AWGN channels. In Corral-Briones et al., a reduced-state multiuser receiver (RSMR) that jointly decodes the trellis code and equalizes the multiuser interference of the channel has been introduced. In this paper the performance of this reduced-state family is studied for a heavily loaded bandwidth limited communication system. Unlike the previous work we address the performance of RSMR in situations of practical interest such as in high bandwidth efficiency situations and in near-far situations. Simulation results show that performance near the trellis-coded single user bound is achieved with this scheme at a drastically reduced complexity compared with that of the optimal receiver. Moreover we analyze the near-far resistance of RSMR and other suboptimal schemes. Results show that RSMR significantly outperforms previously known suboptimal structures.