EURASIP Journal on Applied Signal Processing
Volume 2006 (2006), Article ID 91919, 10 pages
doi:10.1155/ASP/2006/91919
Efficient Closed-Loop Schemes for MIMO-OFDM-Based WLANs
1Department of Electrical and Computer Engineering, University of Florida, Gainesville 32611-6130, FL, USA
2Department of Electrical and Computer Engineering, University of Colorado, Boulder 80309-0425, CO, USA
Received 28 December 2005; Revised 18 July 2006; Accepted 13 August 2006
Copyright © 2006 Xiayu Zheng 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
The single-input single-output (SISO) orthogonal frequency-division multiplexing (OFDM) systems for wireless local area networks (WLAN) defined by the IEEE 802.11a standard can support data rates up to 54 Mbps. In this paper, we consider deploying two transmit and two receive antennas to increase the data rate up to 108 Mbps. Applying our recent multiple-input multiple-output (MIMO) transceiver designs, that is, the geometric mean decomposition (GMD) and the uniform channel decomposition (UCD) schemes, we propose simple and efficient closed-loop MIMO-OFDM designs for much improved performance, compared to the standard singular value decomposition (SVD) based schemes as well as the open-loop V-BLAST (vertical Bell Labs layered space-time) based counterparts. In the explicit feedback mode, precoder feedback is needed for the proposed schemes. We show that the overhead of feedback can be made very moderate by using a vector quantization method. In the time-division duplex (TDD) mode where the channel reciprocity is exploited, our schemes turn out to be robust against the mismatch between the uplink and downlink channels. The advantages of our schemes are demonstrated via extensive numerical examples.