Approximate Belief-Selective Propagation Detector for Massive MIMO Systems

When faced with challenging antenna configurations or high-order modulations in realistic propagation environments, the Belief Propagation (BP) MIMO detector outperforms its linear counterparts. To mitigate the error floor issue and lower the complexity, a revised BP detector, named the Belief-selective Propagation (BsP) detector, has recently emerged by selectively utilizing trusted incoming messages for updates. Despite those promising potentials, the straightforward hardware implementation of the BsP detector still suffers from high complexity and necessitates further optimization. To bridge the gap between the BsP algorithm and implementation, this paper introduces an approximate but implementation-friendly BsP detector called aBsP, based on which the very first BsP hardware is proposed. Two unexplored features: approximate initialization and simplified message updates save the complexity (more than 84%) with acceptable performance penalization. Multi-level optimization techniques involving group-layered message updating, approximate arithmetic circuits, and hybrid-precise quantization are developed to boost the hardware efficiency. A 128\times 8\,\,256 -QAM aBsP MIMO detector ASIC in 40 nm CMOS occupies an area of 0.68 mm2 and reaches a throughput of 790.52 Mbps. Benchmarking with the recent arts, this work achieves 1.08\times area efficiency and 3.34\times gate efficiency.