A Reservation-based MAC Protocol For Underwater Acoustic Sensor Network

With the deepening of people's understanding of the ocean,underwater wireless sensor networks have attracted more and more attention in recent years.They can improve ocean exploration and meet the needs of various appli cations.However,due to the late start of underwater sensor networks in my country,the development level of underwater sensor networks is still relatively backward compared with developed countries.As one of the underlying foundations of underwater wireless sensor networks,the Medium Access Control Layer(MAC)coordinates the access of network nodes to the shared wireless media to prevent conflicts caused by data transmission between nodes in the network,and to achieve higher network throughput,higher energy efficiency,lower channel access delay and fairness of communication channel occupation among network nodes.Due to the characteristics of underwater acoustic channel,such as long propagation delay,limited available bandwidth and serious noise,t he MAC protocol of land sensor network cannot be well applied in underwater sensor network.Therefore,it is essential to design a new MAC protocol according to the application scenarios of underwater sensor networks and the characteristics of underwater acoustic channels.At present,the main idea of MAC protocol research in underwater sensor network is to overcome the adverse effect of long propagation delay and improve energy efficiency.To make full use of the full bandwidth of the underwater acoustic channel and avoid data frame collisions,many competing MAC protocols based on reservation ideas have been studied.However,the large number of control frame transmissions and long-time monitoring of the channel lead to high energy consumption in these p rotocols.Due to factors such as the long propagation delay of the underwater acoustic channel and the difficulty of battery replacement in the harsh underwater environment,the research on the MAC protocol of the underwater sensor network needs to overcome the adverse effects of the long propagation delay of the underwater acoustic channel on the data link and improve energy efficiency.This paper proposes a reservation-based on-demand assignment MAC protocol for Underwater Acoustic Sensor Networks(RDA-MAC).Firstly,the base station node maps the events of the terminal node to its timeline,and converts the physically long propagation delay network into a virtual wireless network in cyberspace.Secondly,the protocol makes nodes go to sleep at an appropriate time and reduces the transmission of control frames to achieve better energy efficiency.Finally,the protocol can completely avoid the collision of MAC frames,which achieves higher network throughput.Compared with the Aloha and the Slotted-FAMA,the experimental results show that the protocol has higher network throughput,lower end-to-end latency and better energy efficiency.With the rapid development of underwater vehicles,this paper proposes a reservation-based on-demand assignment MAC protocol for mobile nodes in Underwater Acoustic Sensor Networks(RDA-M-MAC),which allows a potential mobile node to reserve a channel by setting aside a period time during the channel reservation phase.Compared with Aloha and Slotted-FAMA,the experimental results show that RDA-M-MAC still has better network performance in the scenario with multiple mobile nodes.The two protocols designed in this paper fully demonstrate that the conflict of data frames and control frames has a great impact on the performance of underwater sensor networks,which provides directions for future research on MAC protocols of underwater sensor networks.