RADAR: Rate-Alert Dynamic RTS/CTS Exchange for Performance Enhancement in Multi-Rate Wireless Networks

Rate adaptation is a common technique to exploit channel diversity in wireless networks. Despite the many rate adaptation algorithms proposed for 802.11 networks, the ARF (auto rate fallback) remains the most widely adopted scheme in commercial 802.11 products due to its simplicity. However, ARF suffers from some disadvantages. Our research effort revealed the rate avalanche effect that could significantly degrade the network performance of heavily loaded 802.11 networks. In this work, we propose RADAR (Rate-Alert DynAmic Rts/cts exchange) to judiciously exploit dynamic RTS/CTS exchange in multi-rate 802.11 networks. RADAR could effectively suppress the rate avalanche effect while at the same time minimizes the transmission overhead of RTS/CTS exchanges. Being fully compatible with current 802.11 standards, RADAR can be readily implemented in the NIC driver. Through extensive simulations using realistic channel propagation and reception models, we demonstrate that RADAR is a practical and efficient performance enhancement approach for multi-rate 802.11 networks.