Low complexity soft-output signal detector for spatial-multiplexing MIMO system

This paper presents a cost-efficient soft-output signal detector design solution targeting on the spatial-multiplexing MIMO system. The detector achieves low hardware cost and near-optimal detection performance based on the modification to the fixed-complexity sphere decoder (FSD) using several implementation-oriented algorithm-level improvements, which are early-pruning with polygon-shaped constraint, symbol-level bit-flipping, and ℓ¹-norm approximation. To evaluate the proposed method, we implement the MIMO detector in a 65-nm standard V_T CMOS technology. The core area is 0.14 mm² with 69 K equivalent gates, representing a 60% hardware-resource saving to the state-of-the-art in the open literature. The detecting throughput is up to 1.5Gb/s at 250-MHz clock frequency and 1.2-V supply. The normalized energy consumption of 36.4 pJ/b is shown to be the most energy-efficient design compared with other soft-output detectors.