Transmission rate control through MAC layer acknowledgements feedback

Ad hoc networks suffer from unfairness when multiple flows exist in the same interference region. The unfair channel distribution among competing flows is due to the random exponential back off algorithm used by the IEEE 802.11 Medium Access Control (MAC) protocol. The protocol can lead to unfair channel utilization among different flows, as some of the nodes may capture the channel for a long period leaving the competing nodes to starve. This paper introduces a novel algorithm named Transmission Rate Control through Acknowledgements Feedback (TRCAF), which controls the channel resources distribution through feedback, included in MAC layer acknowledgements, about the status of the network. The signaling determines whether the intermediate nodes carry on transmitting or stop in order to help the starving nodes to gain access to the channel. In addition, the TRCAF algorithm integrates a scheme that improves fairness in situations where there is no information about the status of the network through monitoring the severity of packet collisions that nodes experience. Simulation results show that the TRCAF algorithm achieves 99% fairness, in contrast to the standard MAC protocol that achieves only 33% under comparable overall utilization of the channel resources.