Low-Complexity Spatial-Frequency-Time-Domain MMSE Multiuser Detectors for MC DS-CDMA

Abstract

This paper presents three multiuser detectors (MUDs) for the uplinks of spatial-frequency-time-domain (SFT-domain) spread multi-carrier (MC) direct sequence code division multiple access (DS-CDMA) systems. First, aiming at achieving significant performance gain, we propose a joint optimum SFT-domain MUD based on minimum mean square error (MMSE) decision rules. Further, to reduce the computational complexity, we decompose the SFT-domain received signal to low-dimension signal components and propose the corresponding separate MMSE MUDs. Complexity analysis and computer simulations show that the joint optimum SFT-domain MMSE MUD performs the best among the proposed schemes. Meanwhile, the separate MMSE MUDs can provide effective performance close to that of the joint optimum SFT-domain MMSE MUD but with a modest computational overhead.