A low-latency high-throughput soft-output signal detector for spatial multiplexing MIMO systems

This paper presents a low latency, high throughput soft-output signal detector for a 4 × 4 64-QAM spatial-multiplexing MIMO system. To achieve high data-level parallelism and accurate soft information, the detector adopts a channel-adaptive node perturbation technique to generate a list of candidate vectors around an initial linear estimation. The detection algorithm provides a large range and convenient performance-complexity trade-off by adjusting the node perturbation parameter. A partial-parallel pipelined VLSI architecture is developed to implement the algorithm with high throughput, low processing latency, while offering the flexibility to support run-time performance tuning. Moreover, a fast and hardware-friendly node enumeration scheme is developed to further reduce the processing delay by exploiting the geometric property of the quadrature amplitude modulation (QAM) constellation. The detector was synthesized using Synopsys Design Compiler with a 65 nm CMOS standard cell library. The core area is 0.58 mm2 with 290 K gates. The peak throughput is 3 Gb/s at 500 MHz clock frequency with a latency of 20 ns. Compared to other reported soft-output MIMO detectors, this is a latency reduction of 71%. The corresponding energy consumption is 33 pJ per bit detection.