Research On MAC Protocol For Underwater Acoustic Networks Based On Concurrent Scheduling

Underwater acoustic networks have extensive application prospects,such as marine resource exploration,marine ecological monitoring,marine electronic information industry,marine military and other fields.Due to the absorption of water,radio waves and light waves attenuate heavily in the process of underwater communication and cannot achieve long-distance communication,therefore,underwater sensor networks employ acoustic signals for communication.The communications of underwater acoustic networks have the characteristics of long latency and high energy consumption,the underwater acoustic channels have the characteristics of low available bandwidth and high bit error rate,these factors make the traditional terrestrial wireless sensor networks protocol unable to be applied to the underwater acoustic networks.Therefore,the underwater acoustic networks need tailored network protocols.The protocols of the underwater acoustic networks include underwater routing protocols,medium access control(MAC),and reliable transmission mechanisms.A MAC protocol is mainly responsible for coordinating and controlling the channel resources of the underwater acoustic networks.Thus,it has an important impact on the performance of the underwater acoustic networks with limited bandwidth sharing channel.In this thesis we deeply analyze the characteristics of underwater acoustic networks,such as long delay,low channel utilization,low throughput,and the challenge problems of underwater acoustic networks,such as temporal-spatial uncertainty,hidden terminals.Then we propose a new Concurrent Scheduling MAC(CS-MAC)protocol for underwater acoustic networks.The specific implementation of CS-MAC protocol is divided into three stages: network initialization stage,handshaking stage and transmission stage.The main works are as following.1.The protocol breaks the the mode of traditional one sender-one receiver transmission with handshaking mechanism and realizes concurrent transmission from multiple sending nodes to one receiving node,consequently improves the channel utilization,network throughput and other performance metrics.2.To ensure that the receiving times of packets from different senders does not overlap at the same receiving node,the distances between the receiving node and multiple sending nodes are fully considered,and the temporal-spatial uncertainty of the underwater acoustic networks is effectively used to schedule the sending time of the sending nodes.Further,the information such as the ID,location,level and scheduling time is exchanged between the receiving node and the sending nodes through the handshaking frame,which avoids collision at the receiving node to a great extent and reduces packet retransmission while solving the hidden terminal problem of underwater acoustic networks.3.Based on the Markov-chain model,the thesis analyzes the states of the nodes in handshaking stage,deduces the transmission probability,and analyzes the throughput performance of the CS-MAC protocol through mathematical theory.4.The performance of CS-MAC protocol is comprehensively tested and verified by NS3 simulation platform,and the performance of CS-MAC protocol is compared with classical underwater MAC protocols such as ALOHA,R-MAC,and Slotted-FAMA,etc.The simulation results shows that the network throughput of CS-MAC protocol is better than that of ALOHA,R-MAC,and Slotted-FAMA,etc.CS-MAC protocol outperforms ALOHA and LSPB-MAC protocols in terms of packet delivery rate and end-to-end delay.