Improving wireless local area networks goodput through link adaptation and scheduling

The high speed wireless local area network (WLAN) is emerging today as a strong contender for the last hop communication in the Internet. However, due to interference and time varying channel characteristics, the advertised data rates are seldom achieved. Link adaptation is the technique that allows a station to change the characteristics of its links (e.g., modulation scheme, frame size, coding rate, and so on) in order to improve the throughput. In this paper, we propose a link adaptation system that performs per frame fragment rate adaptation to quickly adapt to different channel states. The system comprises an online fragmentation module and a credit based scheduler and relies on a a pre-computed lookup table to determine the appropriate fragment size and rate that maximizes the throughput given the channel condition. Simulations performed under real world signal-to-noise (SNR) values show that the goodput of our system can reach twice that achieved by the well known autorate fallback (ARF) scheme when multiple stations with different channel characteristics co-exist in the network.