A 38 pJ/b Optimal Soft-MIMO Detector

An optimal soft multiple-input multiple-output (MIMO) detector is proposed with linear complexity for a general spatial multiplexing system with two transmitting symbols and N
_R
≥ 2 receiving antennas. The computational complexity of the proposed scheme is independent of the operating signal-to-noise ratio and grows linearly with the constellation order. It provides the soft maximum-likelihood solution using an efficient log-likelihood ratio calculation method, avoiding the exhaustive search on all the candidate nodes. Moreover, an efficient pipelined hardware implementation of the detection algorithm is proposed, which is fabricated and fully tested in a 130-nm CMOS technology. Operating at 1.2 V supply with 412-MHz clock, the chip achieves up to 5 Gb/s throughput with 192-mW power dissipation and an energy efficiency of 38 pJ/b, showing great potential to be used in next generation Gbps wireless systems. The proposed MIMO detector is perfectly suitable to be applied to the long-term evolution modem as well as Wi-Fi and WiGig devices with more than 1 RF chain. Synthesis results in a 90-nm CMOS technology demonstrate that the design can operate at a sustained throughput of 6.2 Gb/s and an energy efficiency of 28 pJ/b at 1.2 V supply. For applications demanding a lower throughput regime, the core can operate at 0.9 V supply consuming 42 mW providing a throughput of 1 Gb/s
¹
.