Reduced-complexity receivers for space-time coded DS-CDMA systems
Global Telecommunications Conference, 2002. GLOBECOM '02. IEEE
The combination of space-time coding and multiuser detection is an effective way to increase the spechl efficiency of multiple access systems. In this paper we propose a new multiuser decoder for space-time coded asynchronous D S CDMA systems over Rayleigh fading channels. The proposed scheme is an extension of the one introduced in 111. Complexity is reduced exploiting the lact that the trellis for the entire decoder can he decomposed into a set of trellises for subsets of users with a lower
... sers with a lower total state count. Dimerent tradwffs between performance aud complexity can he achieved by adjusting the number of users decoded by each trellis. We investigate the behavior of the proposed receiver for a few users with moderate and high correlation. Simulation results show that the new scheme achiwes an order of magnitude lower error rate than the Conventional receiver (i.e., B single-user decoder that ignores multiuser interference) at almost the same complexity. Moreover, doubling the complexity, the proposed receiver performs near the single user bound We also address the performance and complexity of the new scheme in high bandwidth efficiency sltuations, which are 01 high practical interest. It is found that performance close to the single user hound is achieved with our scheme at practical lrame ermr rates with sigNPcantly lower complexity than therecelver proposed in [I].