On Link Rate Adaptation in 802.11n WLANs

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The IEEE 802.11n standard is gaining popularity to achieve high throughput in wireless LANs. In this paper, the authors explore link adaptation in practical 802.11n systems using experiments with off-the-shelf hardware. The experiments reveal several non-trivial insights. Specifically, trivial extensions of algorithms developed for 802.11g provide minimal benefits in 802.11n systems; in contrast to theoretical expectation, multiple antenna transmission does not always lead to higher throughput in practice; both stream and antenna selection are essential to reap the full benefits of MIMO technologies. They use insights developed from experiments to develop a new metric for stream selection called the Median Multiplexing Factor (MMF).