低轨卫星LTE通信系统同步问题的研究

发布时间：2019-03-18 20:12

【摘要】：低轨卫星通信系统可以实现全球无缝覆盖,解决地面通信网的盲区覆盖问题或稀有用户密度区域的基本通信问题,同时在出现自然灾害或热点地区,作为地面通信网的备份和补充。以蜂窝技术为起点,地面移动通信近年来得到了快速的发展,为实现更高的数据通信速率,3GPP提出OFDMA技术和MIMO技术,经过多年研究最终提出了LTE通信协议。近几年来LTE应用技术的快速发展,将LTE技术应用于低轨卫星的通信系统成为了一个全新的研究热点。本文研究了LTE协议在低轨卫星场景中的应用,分析卫星信道的特点,提出了低轨卫星信道模型,采用LTE通信协议中的关键技术搭建并改进适应低轨卫星的上行链路系统。同时本文的仿真分析大都基于该卫星上行链路系统。本论文首先分析研究了LTE上行随机接入与同步的过程,分析并提出了LTE标准应用于低轨卫星场景会产生的问题。设计新的前导序列结构以适应长时延的低轨卫星环境,并仿真验证在卫星链路中新前导序列结构的检测性能。针对LTE系统应用到低轨卫星上时由于大多普勒频移带来的频率不同步问题,本文分析研究了频率偏移的估计算法,并根据低轨卫星的应用场景对整数频偏的估计算法加以改进,并进行仿真验证其估计性能。最后分析研究传统的地面LTE系统中的定时提前量TA问题,提出了适应于低轨卫星大时延场景下的定时提前量策略。同时针对卫星链路下发射端与接收端存在定时误差的问题,采用现有的定时偏移估计算法进行补偿,并对现有的时偏估计算法进行改进,通过仿真验证算法的估计性能,实现了低轨卫星定时偏移的估计与补偿,提升了链路系统的通信性能。
[Abstract]:Leo satellite communication system can achieve seamless global coverage, solve the problem of blind area coverage of terrestrial communication network or the basic communication problem of rare user density area, and at the same time, in areas of natural disasters or hot spots, As a backup and supplement of terrestrial communication network. Based on cellular technology, terrestrial mobile communication has been developed rapidly in recent years. In order to achieve higher data communication rate, 3GPP proposed OFDMA and MIMO technology, and finally proposed LTE communication protocol after many years of research. With the rapid development of LTE application technology in recent years, the application of LTE technology to Leo satellite communication system has become a new research hotspot. In this paper, the application of LTE protocol in Leo satellite scenario is studied, the characteristics of satellite channel are analyzed, the channel model of Leo satellite is proposed, and the key technology of LTE communication protocol is used to build and improve the uplink system adapted to Leo satellite. At the same time, the simulation analysis of this paper is mostly based on the satellite uplink system. In this paper, the process of LTE uplink random access and synchronization is analyzed and studied, and the problems arising from the application of LTE standard in Leo satellite scenarios are analyzed and proposed. A new preamble sequence structure is designed to adapt to the low-orbit satellite environment with long delay, and the detection performance of the new preamble sequence structure in satellite links is verified by simulation. In order to solve the problem of frequency unsynchronization caused by large Doppler frequency shift when LTE system is applied to Leo satellite, this paper analyzes and studies the estimation algorithm of frequency offset, and improves the estimation algorithm of integer frequency offset according to the application scene of Leo satellite. The estimation performance is verified by simulation. Finally, the problem of TA in the traditional ground LTE system is analyzed, and the strategy of timing advance is proposed, which is suitable for the low-orbit satellite with large time-delay. At the same time, aiming at the problem of timing error between transmitter and receiver under satellite link, the existing timing offset estimation algorithm is used to compensate, and the existing time offset estimation algorithm is improved, and the performance of the algorithm is verified by simulation. The timing offset estimation and compensation of Leo satellite is realized, and the communication performance of the link system is improved.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN927.23

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