Improving MAC Performance in Wireless Ad Hoc Networks Using Enhanced Carrier Sensing (ECS)

In a mobile ad hoc network (MANET), how to maximize the utilization of the limited bandwidth while maintaining fairness among the contending nodes is one of the most challenging issues due to the hidden terminal problem in a multihop scenario. In CSMA/CA-based IEEE 802.11, Carrier Sensing (CS), Collision Avoidance (CA), and Contention Resolution (CR), the three main components of the protocol, affect its performance. While the effects of CA and CR on the performance have been emphasized in the literature, to the best of our knowledge there is no research-work taking into account CS’s effect. In this paper, we focus on the CS mechanism to improve the performance. In the current IEEE 802.11 standards, whenever a node detects an erroneous frame (e.g., a sensing range frame) on the medium, it defers the transmission by a fixed duration (represented by EIFS). We show that this duration is sometimes smaller and sometimes larger than the desired period by which the transmission should be deferred, and it leads to substantial unfairness and throughput degradation. We propose an enhanced carrier sensing (ECS) scheme, which distinguishes among the type of the erroneous frames based on their lengths and defers the transmission accordingly. Simulation results show that the ECS improves the fairness as well as the throughput substantially.