Applying Antenna Selection in WLANs for Achieving Broadband Multimedia Communications

A combination of orthogonal frequency division multiplexing (OFDM) and Multiple-input-multiple-output (MIMO) systems appears to be a promising solution for the PHY layer of indoor multimedia transmission via wireless Local Area Networks (WLANs). Antenna selection is an excellent way of reducing the hardware costs of MIMO-OFDM systems while retaining high performance. This paper addresses two major practical concerns for the application of antenna selection: antenna selection training protocol design, and calibration to solve RF imbalance. We present novel solutions that are especially suitable for slowly time-varying environments, e.g., indoor scenarios, sports stadiums, and shopping malls. Specifically, a low Doppler spread associated with such environments enables us to train all antenna subsets by multiple training packets transmitted in burst; consequently antenna selection techniques can be accommodated in the emerging standards with minimum modifications. In order to deal with RF imbalance, we propose a novel calibration procedure that reduces the performance degradations. Both numerical and analytical approaches are used to verify the effectiveness of the proposed solutions, which make antenna selection more easily adaptable for high-throughput WLAN systems. Our solutions have been accommodated in the current draft of the IEEE 802.11n standard for high-throughput WLANs