无线地下传感网中基于LDPC码的磁感应通信信号传输研究

The original electro magnetic (EM) communication technology can not operate well when it is used in mine monitor, underground pipeline network monitor and soil monitor for its limited underground propagation. Magnetic induction (MI) based wireless underground sensor networks have great potential to be deployed in underground signal propagation. It has high bit error rate, short communication distance for an existing magnetic induction communication system. However, the performance of a magnetic induction communication system can be improved effectively if the optimizing LDPC (Low Density Parity Check) codes are used in the system. We will analyze the effect of underground environment, and consider the target bit error rate, coding rate and energy consumption in this project. Then, we will focus on optimizing LDPC codes toward low energy consumption, high reliability and high frequency efficiency. There are four aspects will be discussed including direct magnetic induction communication, magnetic induction waveguide communication, signal compression and analyzing model for signal transmission. Firstly, we will analyze the influence mechanism of minimum distance and code weight distribution for LDPC codes on coding performance which are used in direct magnetic induction communication and magnetic waveguide communication. Next, we will study QC-LDPC (Quasi-Cyclic LDPC) codes design methods based on the channel model for direct magnetic induction communication system and magnetic induction waveguide communication system respectively. Secondly, we aim to extend the LDPC codes design method to compressed sensing. Furthermore, we will sample the signal using compressed sensing which can decrease the transmission data and reduce the energy consumption of the node. Finally, we will construct a corresponding graph of the sensor networks, and then give a globally analysis model based on the graph signal processing. It is very important for implementation of this project to construct a magnetic induction communication system for the wireless underground sensor networks with low energy consumption and high reliability.

基于磁感应通信的无线地下传感网在矿井监测、土壤监测等传统通信受限场合有重要应用潜力，现有磁感应通信误比特率高、传播距离短，而采用优化设计LDPC码可有效改善通信性能。本课题拟深入分析地下环境中各种因素对信号传输性能的影响，综合考虑目标误码率、编码码率与能耗等因素，围绕低能耗、高可靠性和高频谱利用率，以LDPC码优化设计为核心，分别从直接磁感应信号传输、磁感应波导信号传输、采样信号的压缩及信号传输全局分析模型四个方面开展研究。结合地下环境信道特点，分别在直接磁感应通信、磁感应波导通信方式下，探讨LDPC码的最小距离、码重分布等参数对信号传输性能的影响机制，研究LDPC码优化设计策略；探讨基于LDPC码设计方法的压缩感知信号采样，降低节点能耗，减小传输数据量；构建传感网的图模型，研究基于图信号处理的信号传输全局分析模型。本课题将为无线地下传感网建立低能耗、高可靠性磁感应通信系统打下良好基础。

针对矿井监测、土壤监测、应急救援以及水下环境监测等相关应用，基于LDPC码的磁感应通信系统具有重要应用潜力，结合无线地下传感网的低功耗需求和地下信道环境，解决了磁感应通信系统中QC-LDPC码优化设计、无线双向信息功率传输及功耗优化、无线地下传感网的性能评价以及联合资源分配等关键技术问题，主要工作总结如下，(1)研究了磁感应通信的天线模型及信号传播规律，分析了无线地下（水下）传感网环境中，磁感应通信信号的路径损耗，提出了一种用于磁感应通信的QC-LDPC码优化设计方法，探讨了线圈参数、码参数等和通信距离之间的关系，在得到优化QC-LDPC码同时，还获得了磁感应通信信号传输的最大距离门限值，为无线地下传感网中磁感应通信系统的设计提供了重要指导。(2)面向无线传感网的低功耗信号采集需求，研究了水下无线传感网中，基于磁感应通信辅助的协同MIMO技术信号采样，显著提高了网络覆盖空间和网络吞吐量；在分析信道状态信息统计规律(SCSI)的基础上，提出了一种新的SWIFT NOMA系统中的功耗优化算法，有效延长了传感网中通信节点使用寿命。(3)面向井下安全监测需求，研究了基于IEEE 802.11ah协议的无线地下传感网，随着传感网中节点数量增加，IEEE 802.11ah协议与传统的802.11协议相比，在吞吐量、时延和能耗方面具有明显优势；为提升无线地下传感网的网络整体效率，课题组提出了一种无人机辅助的，全双工-非正交多址无线通信网络的上下行联合资源分配方法，保证用户QoS要求的同时，降低了用户的功耗。仿真结果表明，提出方法在频谱效率和能量效率方面均优于其他方法。(4)在原有地下磁感应通信实验平台基础上，还搭建了水下无线磁感应通信平台，研究了线圈参数、天线角度等与信号传输性能之间的关系，并进行了相关实验验证。课题组共发表论文40篇，其中SCI检索论文25篇；已授权中国发明专利3项，授权国外专利1项，已申请发明专利1项；培养青年教师3名，培养博士研究生1名，硕士研究生3名；依托本课题成果，获得盐城市自然科学优秀学术成果奖二等奖1项。