Research On Marine-Environment-Oriented Heterogeneous Wireless Network System

Marine-environment-oriented heterogeneous wireless network system is the key approach to implement the transmission function of marine information.The research field includes het-erogeneous wireless network software system,MAC layer protocol,routing layer protocol,hard-ware system,and attached subsystems.Compared with traditional wireless communication tech-nologies and networks,the system has a complex system structure and involves a wide range of technologies,including a low-speed underwater acoustic sensor network which consisting of beacons and underwater robots for collecting underwater information;and a high-speed water surface wireless mesh network;and various resources for connecting heterogeneous networks.The various parts of the system are relatively independent and interrelated.To this end,this the-sis starts with the characteristics of heterogeneous networks in the marine environment,deeply analyzes the problems faced by each part,and proposes network optimization schemes to achieve efficient data transmission.It is also a research hotspot of heterogeneous wireless network sys-tems for the marine environment and has received extensive attention from scholars.Through the systematic study of the existing system and work,some deficiencies can be found in the existing marine-environment-oriented heterogeneous wireless network system:poor adaptability of the MAC layer protocol in the underwater acoustic sensor network,which is difficult to dynamically adapt to the network load changes in the high-latency link,resulting in excessive node overhead;and the link scheduling mechanism of the water surface wireless mesh network fails to fully consider the physical layer information of different antennas in the network,as well as the routing protocol,especially the congestion control method in the multi-path routing protocol,which cannot effectively deal with the problem of network fluctuation.Therefore,this paper commences with the heterogeneous network protocols and functions and proposes relevant protocols and solutions:(1)In order to solve the problems of high propagation delay and low communication band-width in the underwater acoustic sensor network communication process,a MAC layer protocol based on network load optimization for the underwater acoustic sensor network is proposed.The protocol starts by reducing the amount of control frames used in the network and takes the load of the network into consideration,i.e.,the receiving node controls the transmission protocol and transmission method of the transmitting node in accordance with the amount of data it receives.This paper compares UPMAC with existing MAC protocols in terms of data throughput,end-to-end delay,and energy consumption under different network topologies through theoretical analysis and simulation experiments demonstrating that the high and low load modes of the pro-tocol can effectively adapt to the network status,reduce node energy consumption and improve network performance.(2)For the optimization of wireless mesh network capacity,this paper commences with the basic features of the physical layer antenna and adds the problems of different types of di-rectional antennas such as interference angle and antenna gain to the link scheduling problem.It proposes an approximate algorithm for solving the MLS problem to schedule the maximum link set for transmission in the same time slot and improve the throughput of the wireless mesh net-work.Based on theoretical analysis and simulation experiments,this paper demonstrates that the directional antenna is more effective than the omnidirectional antenna in suppressing inter-link interference.The proposed directional antenna-based link scheduling algorithm achieves good performance.(3)For the optimization of wireless mesh network capacity,this paper introduced Multi-path Transmission Control Protocol(MPTCP)and thoroughly discussed its congestion control mechanism with the analysis of the inappropriate distribution of congestion windows caused by the lack of analysis of the reasons for packet loss on the path implemented by existing congestion control algorithm.A joint analysis of multiple sub-flows in MPTCP is demonstrated in this pa-per and a method to select the optimal path to improve the throughput of MPTCP and implement the equalization of congestion according to the congestion and bandwidth conditions on the path of each sub-flow is proposed.Based on theoretical analysis and simulation experiments,this paper also proves that this congestion control method significantly improves the performance of MPTCP and the network throughput compared with traditional congestion control mechanisms such as TCP and OLIA.(4)The last section of this paper commences with the establishment of wireless mesh net-work equipment and experimental bed.It introduces the hardware design and software design of the wireless mesh router and carries out its features and performance.Tests were conducted on wireless mesh network related experiments,especially the proposed problems from the per-spective of experiments on directional antennas and link scheduling.This platform provides the indispensable support for the research on Marine-environment-oriented heterogeneous wireless network.