The Impact of Regulatory Transmit Power Constraints on the Relative Performances of Wi-Fi Beamforming and Antenna Selection

This paper analyses the theoretic throughput and coverage for a multi-element in-home Wireless Local Area Network (WLAN) in the 5 GHz band. In particular we study the impact of regulatory transmit power constraints on the relative performances of beamforming and antenna selection at the access point. A novel methodology is applied based on part measurement and part simulation. In home results are provided for standard 802.11n multiple-input multiple-output (MIMO) deployments. Results show that beamforming is particularly affected by regulatory transmit power constraints. For long-range links beamforming data throughputs are reduced by more than 50%. The average data rate in our test home reduces by 14.3% when regulatory constraints are applied to the beamforming system. For antenna selection the regulatory limits result in an 8.9% reduction in average throughput. Furthermore, we show that for long range links the average data rate is improved by 50% when the antenna selection is used in place of beamforming. Although antenna selection uses single stream MIMO more frequently than beamforming, the latter performs better when multiple spatial streams are used. Beamforming is shown to work best in the easy and medium-range channels.