Message Passing Detector for Phase-Shifter-Aided Spatial Multiplexing Over Frequency Selective Channels

Reducing the cost of radio frequency (RF) chains remains a critical challenge in multiple-input multiple-output (MIMO) systems. In this paper, we investigate a novel low-RF-chain technique, termed as phase-shifter-aided spatial multiplexing (PSSM), in the context of frequency-selective channels. Base on the single-carrier frequency-domain equalization (SC-FDE) concept, we develop a message-passing detector specifically tailored for PSSM systems. This detector integrates belief propagation (BP) and expectation propagation (EP) to efficiently leverage prior constraints as well as handling the linear inverse problem. To further reduce computational complexity, a simplification method is then introduced. Simulation results demonstrate that the proposed framework achieves superior performance compared to conventional approaches.