About this Journal Submit a Manuscript Table of Contents
Journal of Electrical and Computer Engineering
Volume 2012 (2012), Article ID 938490, 9 pages
http://dx.doi.org/10.1155/2012/938490
Research Article

A Power-Efficient Soft-Output Detector for Spatial-Multiplexing MIMO Communications

Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan

Received 15 June 2011; Revised 14 September 2011; Accepted 17 November 2011

Academic Editor: Zhiyuan Yan

Copyright © 2012 Hsiao-Chi Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

VLSI implementation of a configurable power-efficient MIMO detector is proposed to support 4 × 4 spatial multiplexing and modulation from QPSK to 64-QAM. A novel tree search algorithm is proposed to enable the detector to provide soft outputs and to be implemented in parallel and pipelined hardware architecture. The frame error rate (FER) of the detector approaches the quasi-optimal sphere decoder, with 0.5-dB degradation. Moreover, the proposed detector can operate at the optimal voltage under different configurations and detect/recover timing error at run time by a novel adaptive voltage scaling technique with double sampling circuitry. The proposed detector, using TSMC 0.18 μm single-poly six-metal CMOS process with a core area of 1 . 1 7 × 1 . 1 7  mm2, provides fixed throughput of 45 Mbps in 64-QAM configuration, 120 Mbps in 16-QAM configuration, and 60 Mbps in QPSK configuration. The normalized power efficiency of the design for 64-QAM and 16-QAM configurations is 1.56 Mbps/mW and 2.53 Mbps/mW, respectively. Compared with the conservative margin-based design, the proposed design achieves a 48.8% power saving.