H-MAC: A Channel-Hopping Based Multi-Channel MAC Protocol for 802.11 Wireless LANs

Abstract

IEEE 802.11 provides a contention-based MAC protocol for single channel wireless environment. Extending IEEE 802.11 to a multi-channel environment not only exploits the bandwidth utilization but also reduces the degree of contentions. However, each station is only equipped with a single antenna, resulting in the situation that station pairs staying on data channels can not maintain the channel usage information which only can be obtained from the control channel. The unavailability of channel utilization can further raise the channel collision problem. This study proposes an efficient 802.11 Multi-Channel MAC protocol, called H-MAC, aiming at maximizing the bandwidth utilization. The proposed protocol adopts the channel hopping sequence (CHS) mechanism to resolve the channel collision problem and reduce the message exchange overhead for switching channels. The proposed H-MAC also exploits the opportunities of spatial reuse, maintains the fairness, and possesses several characteristics including low cache overhead, fewer control packets and collision avoidance. Simulation study shows that the proposed H-MAC protocol largely improve the bandwidth utilization, delay time and throughput while maintaining fairness.