New Hidden Station Detection Scheme for Adaptive RTS/CTS Exchange in IEEE 802.11 WLANs

Abstract

In IEEE 802.11 Wireless Local Area Networks (WLANs), the hidden station problem can increase the collision probability and thus degrade the network throughput significantly. The Request-to-Send/Clear-to-Send (RTS/CTS) exchange may mitigate excessive collision due to hidden stations by reserving the channel before transmitting a data frame. However, it incurs significant bandwidth overhead if there is no hidden station. Although there has been a notable attempt to detect hidden stations so that the RTS/CTS exchange is activated only when hidden stations exist, the previous scheme fails to detect hidden stations if the stations have heterogeneous carrier sense ranges as in the real world. In this paper, we propose a new hidden station detection mechanism, which operates within the framework of our collision detection scheme. Therefore, stations can detect a hidden station without any extra cost while collision detection is being performed. In addition, we propose to transmit the RTS frames at a stronger power level than the nominal transmission power to improve the fairness of hidden stations further. We also propose a dynamic transmit power control strategy during the RTS transmission to mitigate the exposed station problem. Comprehensive simulations show that the adaptive RTS/CTS exchange based on the proposed scheme improves the system throughput as well as fairness in various environments including heterogeneous carrier sense ranges.