DUCHA: A New Dual-Channel MAC Protocol for Multihop Ad Hoc Networks

IEEE 802.11 MAC protocol has been the standard for wireless LANs and is also implemented in many simulation software for mobile ad hoc networks. However, IEEE 802.11 MAC has been shown to be quite inefficient in the multihop mobile environments. Besides the well-known hidden terminal problem and the exposed terminal problem, there also exists the receiver blocking problem, which may result in link/routing failures and unfairness among multiple flows. Moreover, the contention and interference from the upstream and downstream nodes seriously decrease the packet delivery ratio of mulitihop flows. All these problems could lead to the "explosion" of control packets and poor throughput performance. In this paper, we first analyze these anomaly phenomena in multihop mobile ad hoc networks. Then, we present a novel effective random medium access control (MAC) protocol based on IEEE 802.11 MAC protocol. The new MAC protocol uses an out-of-band busy tone and two communication channels, one for control frames and the other for data frames, and can give a comprehensive solution to all the aforementioned problems. Extended simulations demonstrate that our protocol provides a much more stable link layer, greatly improves the spatial reuse, and works effectively in reducing the packet collisions. It improves the throughput by up to 20% for one-hop flows and by up to 5 times for multihop flows under heavy traffic comparing to the IEEE 802.11 MAC