A dual-channel MAC protocol for mobile ad hoc networks

Recent studies have shown that the widely used IEEE 802.11 MAC is considerably inefficient in multihop networks. The inefficiency is due to the hidden terminal problem, the exposed terminal problem, the receiver blocking problem, and the ultra-flow contention problem. These four problems can lead to "explosion" of control packets and hence poor throughput performance. To address these problems, we propose a novel MAC protocol based upon the IEEE 802.11 MAC. The unique features of the proposed MAC protocol are 1) a system architecture with an out-of-band busy tone and two communication channels, one for control frames and the other for data frames, and 2) a message exchange procedure that provides a comprehensive solution to all the aforementioned four problems. Our studies show that the proposed scheme can simultaneously overcome the four problems, greatly improve spatial reuse, and eliminate the collisions of DATA packets. In addition, the simulation results demonstrate that the new scheme provides a more stable link layer with less control overheads and much less routing failures and significantly improves the throughput, as compared to the IEEE 802.11 MAC.