Research On Clustering And Cross-layer Protocol For Fishery Ad Hoc System

China has a vast sea area,numerous ports,and abundant marine resources.Fisheries have always been an important industry in China.With the development of China’s fisheries and Internet of Things technology,we need to develop and update the existing fishery communications equipment to meet the growing demand for maritime communications.The Ad hoc network has the characteristics of no center and self-organization,and can be quickly built without relying on fixed network equipment to adapt to the dynamic change of the network topology.This is consistent with the needs of fishery communications,so Ad hoc networks can be applied to marine communications systems to update outdated fishery communications equipment.This thesis first introduces the concept and characteristics of Ad hoc network,as well as the research status of Ad hoc network by domestic and foreign research scholars.The hot research problems of Ad hoc etworks at home and abroad are mainly concentrated on the network layer routing algorithm and MAC layer channel access algorithm,and these two algorithms determine the performance of the entire network.Therefore,based on the analysis of classic protocols and algorithms in other networks,this thesis proposes two different clustering cross-layer protocols for different scenarios at sea,and performs performance simulation verification with the NS-2 network simulation platform.The main content and results are as follows:1.Aiming at the characteristics of high density of vessels and slow change of network topology when fishing vessels stop at the port or start fishing offshore,a clustered and cross-layer HCHMA protocol is proposed.In the HCHMA protocol,the TDMA mechanism is adopted,and each cycle is divided into two periods of neighbor node discovery and data transmission.During the neighbor discovery period,each node in the cluster performs cellular clustering and the division of 6 smaller time slots according to its own geographic location information.The nodes in the same small time slot randomly compete to transmit HELLO packets to achieve the discovery of neighbor nodes.After the neighbor node discovery period ends,each node calculates to the nearest node to the local cell center based on the acquired geographic location information of the neighbor node and selects it as the cluster head.The node running for the cluster head generates an inter-cluster HELLO packet.Two times the communication range of nodes is used for communication between cluster heads,so that two neighbor cluster heads can be reached in one hop.HELLO packets between clusters are not forwarded,but only propagate to the cluster heads of neighboring clusters.During the data transmission period,the channel access mechanism based on 802.11 is used.When there is a need for data transmission,the cluster head uses the backbone formed by cluster heads and the information of the members in the cluster previously obtained to complete the route search and establishment,and the cluster head is not responsible for data forwarding.Simulation results show that the proposed HCHMA protocol has higher throughput,lower delay and packet loss rate,and better network performance.2.Aiming at the characteristics of different densitys of vessels in different areas when fishing vessels sail from the port to the distant sea,a clustering cross-layer protocol with variable communication radius is proposed.First,the relationship between network density at different node densities and communication radii is studied by simulation,and the optimal communication radius at different densities which makes the network have the highest throughput is given.Using the conclusions obtained by simulation,a clustering cross-layer protocol with variable communication radius is further designed.We set the variable communication radius from small to large as R1,R2,R3 and R4.When detecting the density of neighbor nodes,we still use the TDMA time slot frame in HCHMA protocol and the neighboring node discovery mechanism of cellular clustering,and the radius of the cell is the maximum communication radius of the node R4.After the neighbor node discovery is completed,each node selects one of the four communication radii which can reach the highest throughput according to the node density of the area.In the data transmission phase,a route discovery and establishment mechanism based on AODV is used,and RREQ packets and RREP packets are added with geographic location information and the communication radius the node uses.Simulation results show that the proposed HCVCR protocol has higher throughput than the fixed radius AODV,can withstand greater network load,and has better network performance.3.Designed a routing layer protocol that can run on Zynq and Ad9361 fishing Ad hoc network communication platform,and completed the transplantation.In the PS part of Zynq,the Ad hoc routing protocol is implemented based on the Linux network architecture,which completes the processing of data packets and the operation of the kernel routing table in the Linux operating system.It is verified that the communication platform can operate normally and realize the required functions.