Cluster-Based Spatial–Temporal MAC Scheduling Protocol for Underwater Sensor Networks

Underwater wireless sensor networks (UWSNs) have long propagation delays that cause the problem of spatial–temporal (ST) uncertainty, which is a great challenge to transmission scheduling. To solve the scheduling problem, this article proposes a cluster-based ST medium access control (MAC) scheduling protocol (CSS-MAC). First, the cluster head coefficient is defined according to the number of cluster heads in the node propagation range. Then, with the basic idea that a node with a larger cluster head coefficient transmits at an earlier time, an algorithm to determine the interference nodes is proposed. Second, a new algorithm to create the ST conflict graph (ST-CG) is proposed according to the collision relationship among the nodes. The proposed algorithm avoids the restriction of multiple prohibition times for a single node and greatly simplifies the ST-CG. Finally, a distributed transmission moment allocation algorithm is proposed by interacting with the sending priority and sending time information of the nodes within the two-hop range. In the initialization, this article proposes a clustering algorithm, which ensures that each cluster head node is not within the propagation range of another node for the proposed MAC protocol. The simulation results show that compared with ST-MAC and concurrent scheduling based on ST uncertainty MAC (CSSTU-MAC), the throughput of CSS-MAC increases by approximately 45% and 38% on average, respectively.