A Load-Based Hybrid MAC Protocol for Underwater Wireless Sensor Networks

Ziwei Zhang,Wei Shi,Ying Guo,Qiuna Niu,Hanjiang Luo,Jingjing Wang

doi:10.1109/access.2019.2926158

Abstract

In underwater wireless sensor networks (UWSNs), media access control (MAC) is important because it may have a significant impact on network performance; however, the complex and changeable underwater communication environment is a great challenge for the MAC protocol. In flowing water, the network nodes are constantly moving, and the number of competitors in the network also varies. The existing hybrid MAC protocol neither can adapt to the dynamic network load nor can switch the access control protocols with changing network loads, which may result in poor network performance. In order to solve the above problems, this paper proposes a load-based time slot allocation (LBTSA) protocol. The LBTSA selects the slot allocation scheme, from a set of possible schemes, according to the instantaneous network load. Then, based on the relative priority of the nodes and the optimal number of backoff stages, the host node selects the optimal access control protocol. This not only adapts well to changing network loads but also maximizes network throughput. By assuming that the number of competitors obeys a universal Poisson distribution, the LBSTA protocol and the HCR (a hybrid MAC protocol using channel reservation) protocol are compared. As the results show, the throughput of the LBTSA is higher than that of the HCR protocol, and the end-to-end delay of the LBTSA is lower than that of the HCR protocol.

Highlights

Human underwater activities in oceans have grown rapidly in recent years; a huge number of sensors, actuators and various types of vehicles have already been deployed underwater
The network model and frame structure are presented; in the third section, the design method of a hybrid media access control (MAC) protocol based on load slot allocation for underwater wireless sensor networks is given; the fourth section introduces the underwater acoustic channel propagation loss model and the setting of simulation parameters used in the simulation; the fifth section discusses the simulation results; and the sixth section summarizes the full text
Due to the collision caused by the carrier sense multiple access with collision avoidance (CSMA/CA) protocol, when the number of backoff stages is greater than the optimal number of backoff stages, time division multiple access (TDMA) protocol is chosen by the host node to realize the self-adaptation to the network load The key goal of the protocol is the method by which network load size is evaluated so as to efficiently and dynamically switch the access mode, that is to say, the determination of the critical value is the critical point to be solved