On selecting the best transmission mode for WiFi devices

The design of efficient IEEE 802.11 physical rate adaptation algorithms is a challenging research topic and usually the issues surrounding their implementations on real 802.11 devices are not disclosed. In this paper, we identify and evaluate the key parameters to design such algorithms. We then present a survey on existing physical rate adaptation mechanisms and discuss their advantages and drawbacks. We also propose three new 802.11 physical rate adaptation mechanisms, named AARF, CLARA, and AMRR. AARF, proposed for low-latency systems, has low complexity and obtains similar performance than RBAR in stationary and non-fading wireless channels. CLARA is a culmination of the best attributes of the transmitterbased ARF and RBAR control mechanisms with additional practical features such as adaptive fragmentation to improve multipath fading channel sensing and to provide feedback control signalling. AMRR is designed for highlatency systems; it has been implemented and evaluated on an AR5212-based device. Experimentation results show more than 20% performance improvement in throughput over the default algorithm implemented in the AR5212 MADWIFI driver.