Per-Flow Fair Media Access Control in Wireless Ad-Hoc Networks

IEEE 802.11 [1] is the most widely used protocol in the WANETs. The basic media access control mechanism of IEEE 802.11 is the Distributed Coordination Function (DCF) with Carrier Sensing Multiple Access/Collision Avoidance (CSMA/CA). The DCF includes a backoff algorithm called Binary Exponential Backoff (BEB). The BEB prefers the last successful node because the Contention Window (CW) size of the last successful node is always smaller than those of the unsuccessful nodes. This preference yields unfair channel allocation among the nodes [2]–[4]. Hence, there have been many studies to solve this problem [5]–[7]. However, if all the nodes share the channel fairly, the per-flow throughput of the node transmitting the large number of the flows is lower than that of the node transmitting the small number of the flows. To achieve the per-flow fairness, the authors of [8] introduce a distinct backoff mechanism to all the flows in a node. However, they classify the flows by the service priority not by the source-destination pair. Thus, the algorithm of [8] cannot guarantee to allocate more channel capacity to the nodes having a number of flows. On the other hand, the algorithms of [9]–[11] consider the fairness with the number of flows of a node. However, they cannot guarantee to achieve the maximum throughput and the per-flow fairness simultaneously. In this letter, we propose the Per-flow Fair MAC (PFMAC) to guarantee the per-flow fairness and the maximum network throughput in the single-hop WANETs. In addition, we verify the performance of the PFMAC through the stability analysis and simulations.