Media Access Control Protocols For Underwater Wireless Sensor Networks

Underwater wireless sensor network(UWSNs)have gained tremendous attention in the field of ocean development and communication in recent years.using the sound as the communica-tion medium,UWSNs are characterized by low available bandwidth,long propagation delays and high channel dynamics,which pose grand challenges to the design and analysis of almost every core networking problem.For ocean resource exploration and environmental protection,it is very important to develop the UWSNs.Medium access control(MAC)is a core module of UWSN systems.It is critical to provide valid and efficient MAC solutions for UWSNs.This dissertation focus on the media access control(MAC)protocols in the UWSNs.Based on the channel competition,time scheduling,channel reservation,data train and power control,some MAC protocols are proposed for UWSNs.The main contributions of this dissertation are summarized as follows:(1)In order to solve the multiple RTS attempts problem in slotted-FAMA,a underwater MAC protocol with RTS competition,called RC-SFAMA,is proposed.RC-SFAMA introduces an RTS competition mechanism to choose a winning node when the multiple RTS attempts occur,and then makes the winning node continue completing its data transmission,which improves the throughput.On the basis of RC-SFAMA,a underwater MAC protocol with data train,called SFAMA-DT,is proposed.SFAMA-DT improves the channel utilization by forming a train of data packets of multiple transmission pairs during each round of simultaneously handshakes,which greatly reduces the relative proportion of time wasted due to the propagation delays of control packets and improves the throughput.(2)In order to exploit the long propagation delay and the spatial-temporal uncertainty of acoustic channel,a time scheduled underwater MAC protocol with data train for single-sender multiple-receiver(SM-TMAC-DT)and a time scheduled underwater MAC protocol with data train for multiple-sender single-receiver(MS-TM AC-DT)are proposed.Via the time scheduled scheme,all the nodes in both SM-TMAC-DT and MS-TMAC-DT successfully transmit the data packets in an arranged order without collision.(3)In order to reduce the cost of competition and improve the utilization of underwater acous-tic channel,a reservation based MAC protocol with data train is proposed for the UWSNs,called RMAC-DT.In the RMAC-DT,a reservation period and a reservation confirmation period are in-troduced before the data transmission.Utilizing the RTS-CTS,the channel is reserved and the data packets are sorted in these periods.After the reservation period and the reservation confirmation period,all the data packets are transmitted in an arranged order.These schemes reduce the node's average reservation time,and effectively improve the network throughput(4)In order to improve the energy efficiency of the UWSNs,a underwater MAC protocol with power control is proposed,called MACA-PC.Similar to the basic power control scheme,MACA-PC uses lower transmission power to send data packets.Differently,MACA-PC periodi-cally adds Notification Signal(NS)with the maximum transmission power during the data packets transmission to inform other nodes to avoid collisions.