Location And Time Slot Based Cross-layer Protocol Design For Fishery Ad Hoc System

With the rapid development of Chinese marine economy,the level of fishery communication equipment are needed to be further improved to meet the increasing demand of marine communication.The Ad Hoc network,which can change topology dynamically,can be quickly built without relying on fixed network equipment.And the Ad hoc network has the characteristics of centerless and self-organizing,which is consistent with the characteristics of the marine communication environment.Therefore,the performance of the fishing communication network can be improved by combining the marine fishing communication with the networking technology of the Ad Hoc network.First of all,this thesis introduces the basic concepts and characteristics of mobile Ad Hoc network.Based on an in-depth study of the current domestic and overseas research status of Ad Hoc network,we focuse on the research of hierarchical layered mode of Ad Hoc network.As the channel access protocol of the MAC layer and the routing algorithm of the network layer,which are the core technologies of Ad Hoc network,determine the overall performance of the network,we analyzed the classic MAC protocol and routing algorithm,too.Secondly,on the basis of learning from the classical protocol and analyzing the advantages of honeycomb clustering,this thesis designs a cross-layer protocol based on geographical location and time slot,and then some innovative research results are obtained.Finally,NS-2 network simulation platform is used for performance simulation verification.The main achievements are as follows:1.ND_HC algorithm is proposed to improve the performance of neighbor nodes discovery process.In the ND_HC algorithm,the node is firstly clustered by using geographic location information and honeycomb clustering algorithm.Secondly,the independent division of time complete the neighbor node discovery process.Each cell cluster is divided into six equilateral triangle and time frame is allocated to each triangle.Then the random backoff algorithm is performed for the nodes in each triangle area during its allocated frame to realize the process of neighbor node discovery.Simulation results show that compared the neighbor discovery performance of AODV protocol with 802.11 mechanism,the proposed ND_HC algorithm has higher success probability and shorter time of neighbor discovery.2.TCD_HC algorithm is proposed to improve the performance of network topology discovery process.In TCD_HC algorithm,the node first uses ND_HC algorithm to complete the process of neighbor node discovery.Then,according to the location information of neighbor nodes in the same cell cluster,the distance between each neighbor node and the center of the cell cluster is calculated in a distributed way to complete the race of the cluster head.Finally,the cluster head generates TC packets periodically,which contains the node information of the cluster and the specific geographical location of the cluster head node,so as to realize the information interaction of all nodes in the network.In TCD_HC algorithm,the cluster head will be reduced to a quarter of the original communication rate to get nearly 2 times the range of communication,which makes the TC packets are able to jump up between the adjacent cluster head.TC packets in the network can be forwarded by the cluster heads or the nodes appointed by cluster head,while nodes within the cluster only receive information and do not produce or forward the TC packets.This mechanism makes TCD_HC algorithm reduce the routing overhead and effectively complete the entire network topology discovery.Simulation results show that compared with the active routing protocol OLSR with 802.11 mechanism,the proposed TCD_HC algorithm has lower routing cost and shorter time in the whole network topology discovery.3.Cross-layer protocol HCPT based on position and time slot is developed,too.In the HCPT protocol,TDMA mechanism is adopted to divide the time into time slices.In each time slice,the time is divided into neighbor node discovery time and data transmission time.In the period of neighbor node discovery,ND_HC algorithm is used to complete the process of neighbor node discovery.In the data transmission period,TCD_HC algorithm is used to carry out TC packets interaction among cluster heads,so as to obtain node distribution information and specific geographical location of cluster heads in each cellular cluster in the network.In terms of channel access mechanism,by using RTS/CTS to control the reserved channel and DATA/ACK to comform the data reveiving,the DATA transmission process can be completed between nodes,which improves the reliability of the network.When there exists data transmission request,the node selects the relay node for data forwarding based on the geographical location of the cluster head of the destination node in the routing table and the greedy principle.The network performance of OLSR,AODV and HCPT under different network loads is simulated.Simulation results show that the proposed HCPT protocol has higher throughput,lower packet loss rate and delay,and can transmit data more efficiently.Therefore,the HCPT cross-layer protocol has better network performance and good adaptability for mobile Ad Hoc network topology changes,which provides a reference for the actual construction of marine wireless Ad Hoc network.