Fairness-Enhanced Multiple Control Channels MAC for Ad Hoc Networks

Abstract

The throughput in IEEE 802.11 ad hoc networks can be improved by exploiting the presence of multiple channels and thus allowing multiple nodes to transmit concurrently on different channels. This has been shown by previous work. Some multi-channel MAC protocols use one control channel for exchanging control messages in order to assign concurrently different data channels to different pairs of nodes. On one hand, this previous work does not discuss how to use the control channel, and assumes that the IEEE 802.11 MAC mechanism is used for control packets transmission. Furthermore, no previous multiple channel related study has discussed the fairness performance. In this paper, based on a simple example, we show that deafness and unfairness problems can take place when using multiple data channels. We propose a new medium access control algorithm for control packets to better use the wireless medium. On the other hand, given a large number of available channels, using only one control channel limits the number of useful data channels since only a few nodes succeed in negotiating data channels. This is called control channel saturation in J. So et al. (2004). We therefore propose a new multi-control channels medium access control (MCMAC) protocol, characterized by the following features: (1) the number of control channels used concurrently is a function of the total number of available channels and the data packet size; (2) these control channels are used concurrently to negotiate different subsets of data channels, and each subset of data channels is attributed to each control channel.