OCA-MAC: Opportunistic Channel Aggregation for Wireless Ad Hoc Networks

This paper introduces the Opportunistic Channel Aggregation MAC protocol (OCA-MAC) for wireless ad hoc networks. OCA-MAC allows opportunistic MAC-level channel aggregation per frame transmission. To accomplish that, OCA-MAC is built on top of the IEEE 802.11 DCF MAC with a secondary radio interface for opportunistic access over an alternative channel. OCA-MAC avoids the use of extra control channel for coordination among nodes (or control frame exchanges over the secondary channel) by using the simple idea that whoever acquires the floor over the primary channel also gains immediate (and implicit) right to transmit a frame over the secondary channel (if available at both sides of the link at the time of floor acquisition). Thus, all control information for distributed channel aggregation is carried out over the primary channel, allowing the use of the secondary channel for data frame transmissions only. The gains in performance of OCA-MAC with respect to IEEE 802.11 DCF MAC is evaluated by simulations with topologies not fully connected under saturated traffic. The investigated scenarios indicate that geographical sparsity and spatial reuse do not necessarily lead to performance improvements of IEEE 802.11 networks and, thus, opportunistic channel aggregation proves to be a strong ally to boost throughput and fairness performance in such scenarios.