Multi-Phased Carrier Sense Multiple Access with Collision Resolution and its Extension to Dynamic Multi-Phases

To improve the efficiency of carrier sense multiple access (CSMA)-based medium access control (MAC) protocol, CSMA with collision resolution (CSMA/CR) has been proposed. In the CSMA/CR protocol, a transmitting station can detect a collision by employing additional carrier sensing after the start of data transmission and resolve the next collision that might occur by broadcasting a jam signal during a collision detection (CD) period. By extending this original CSMA/CR protocol that uses a single CD phase, in this paper we propose a multi-phased CSMA/CR (MP-CSMA/CR) protocol that employs multiple CD phases. In the proposed MP-CSMA/CR protocol, colliding stations are filtered in each CD phase, and only surviving stations compete again in the next CD phase. Therefore, the collision resolution probability becomes higher as the CD phases proceed. Utilizing the multiple CD phases, we analyze the throughput numerically and find optimal operating parameters–such as the number of CD phases and the number of CD slots per phase–that maximize the throughput. Based on this result, we also propose a dynamic MP-CSMA/CR protocol in which the number of CD phases is dynamically changed to suit network conditions. Analysis and simulation results show that the proposed MP-CSMA/CR protocol significantly outperforms CSMA/CR with a single CD phase. The dynamic MP-CSMA/CR protocol achieves a slightly better throughput than MP-CSMA/CR, which uses a fixed optimal number of CD phases.