P-CSMA: A Priority-Based CSMA Protocol for Multi-Hop Linear Wireless Networks

In this paper we consider a multi-hop wireless network, where a source transmits data to a destination node, through a route composed of multiple relays which are randomly distributed over a line. Priority-based Carrier-Sense Multiple Access (P-CSMA), a novel Medium Access Control (MAC) protocol, is proposed. According to the protocol, when accessing the radio channel different levels of priority are assigned to nodes, depending on their positions in the route: nodes closer to the destination have higher priority with respect to those closer to the source. The priority in the access to the channel is managed by assigning to nodes different durations of the sensing phase. This mechanism speeds up the transmission of packets which are already in the route, making the transmission flow more efficient. Results show that P-CSMA outperforms existing contention-basedMAC protocols, like p-persistent CSMA and Slotted ALOHA. A mathematical model to derive the performance in terms of packet success probability and average throughput is also provided. The model represents an effective tool for the performance analysis of multi-hop CSMA-based wireless networks, when accounting for interference, due to the hidden terminal node problem.