Algorithm and implementation of the K-best sphere decoding for MIMO detection

K-best Schnorr-Euchner (KSE) decoding algorithm is proposed in this paper to approach near-maximum-likelihood (ML) performance for multiple-input-multiple-output (MIMO) detection. As a low complexity MIMO decoding algorithm, the KSE is shown to be suitable for very large scale integration (VLSI) implementations and be capable of supporting soft outputs. Modified KSE (MKSE) decoding algorithm is further proposed to improve the performance of the soft-output KSE with minor modifications. Moreover, a VLSI architecture is proposed for both algorithms. There are several low complexity and low-power features incorporated in the proposed algorithms and the VLSI architecture. The proposed hard-output KSE decoder and the soft-output MKSE decoder is implemented for 4×4 16-quadrature amplitude modulation (QAM) MIMO detection in a 0.35-μm and a 0.13-μm CMOS technology, respectively. The implemented hard-output KSE chip core is 5.76 mm² with 91 K gates. The KSE decoding throughput is up to 53.3 Mb/s with a core power consumption of 626 mW at 100 MHz clock frequency and 2.8 V supply. The implemented soft-output MKSE chip can achieve a decoding throughput of more than 100 Mb/s with a 0.56 mm² core area and 97 K gates. The implementation results show that it is feasible to achieve near-ML performance and high detection throughput for a 4×4 16-QAM MIMO system using the proposed algorithms and the VLSI architecture with reasonable complexity.