IMAC: Improved Medium Access Control for multi-channel multi-hop wireless networks

Trends in wireless networks are increasingly pointing towards a future with multi-hop networks deployed in multi-channel environments. In this paper, we present the design for iMAC - a protocol targeted at Medium Access Control in such environments. iMAC uses control packets on a common control channel to facilitate a three-way handshake between the sender and the receiver for every packet transmission. This handshake enables the sender and the receiver to come to a consensus on a channel to use for data transmission and also signals to neighboring nodes about the contention on that channel. iMAC then uses a mechanism similar to 802.11 for data communication. Our evaluation of iMAC shows that it provides significant gains in throughput in comparison with uninformed channel selection, especially when contention for channel bandwidth is neither too low nor too high; intelligent selection of channels by iMAC is necessary to harness available bandwidth resources in the presence of medium levels of contention.