Randomly Ranked Mini Slots for Fair and Efficient Medium Access Control in Ad Hoc Networks

Ad hoc networks offer infrastructure free operation, where no entity can provide reliable coordination among nodes. Medium Access Control (MAC) protocols in such a network must overcome the inherent unreliability of the network and provide high throughput and adequate fairness to the different flows of traffic. In this paper we propose a MAC protocol that can achieve an excellent balance between throughput and fairness. Our protocol has two versions. Randomly Ranked Mini Slots (RRMS) utilizes control-message handshakes similar to IEEE 802.11. Randomly Ranked Mini Slots with Busy Tone (RRMSBT) is the better performer of the two but requires a receiver busy tone. The protocol makes use of granule time slots and sequences of pseudo random numbers to maximize spatial reuse and divide the throughput fairly among nodes. We demonstrate the performance of this protocol using simulation with fixed and random topologies, and show that these results are robust to difficult network configurations and unsynchronized clocks. We further develop novel metrics of long-term and short-term fairness for rigorous performance evaluation. Our simulation results include detailed comparison between the proposed protocol and existing protocols that have been shown to excel in terms of throughput or fairness