An adaptive multirate IEEE 802.11 wireless LAN

In order to enhance the system capacity of wireless LANs, we propose in this paper using the frame-based adaptive multirate transmission scheme in the IEEE 802.11 and evaluate its performance. Typically, high-speed modulation schemes would require higher SNR to maintain the transmission quality and BER. The transmission rate is selected dynamically based on the detected SNR, each frame shall be transmitted at the highest available rate. The original virtual carrier sense mechanism in IEEE 802.11 is no longer suitable because the multirate hidden terminal problem. We redefine the MAC header and modify the reservation scheme of the network allocation vector (NAV) to resolve these problems. The throughput and delay are evaluated using simulations and the results show that they can be significantly improved compared with those of the single-rate WLAN