【摘要】：低軌衛(wèi)星通信系統(tǒng)可以實(shí)現(xiàn)全球無縫覆蓋,解決地面通信網(wǎng)的盲區(qū)覆蓋問題或稀有用戶密度區(qū)域的基本通信問題,同時(shí)在出現(xiàn)自然災(zāi)害或熱點(diǎn)地區(qū),作為地面通信網(wǎng)的備份和補(bǔ)充。以蜂窩技術(shù)為起點(diǎn),地面移動(dòng)通信近年來得到了快速的發(fā)展,為實(shí)現(xiàn)更高的數(shù)據(jù)通信速率,3GPP提出OFDMA技術(shù)和MIMO技術(shù),經(jīng)過多年研究最終提出了LTE通信協(xié)議。近幾年來LTE應(yīng)用技術(shù)的快速發(fā)展,將LTE技術(shù)應(yīng)用于低軌衛(wèi)星的通信系統(tǒng)成為了一個(gè)全新的研究熱點(diǎn)。本文研究了LTE協(xié)議在低軌衛(wèi)星場景中的應(yīng)用,分析衛(wèi)星信道的特點(diǎn),提出了低軌衛(wèi)星信道模型,采用LTE通信協(xié)議中的關(guān)鍵技術(shù)搭建并改進(jìn)適應(yīng)低軌衛(wèi)星的上行鏈路系統(tǒng)。同時(shí)本文的仿真分析大都基于該衛(wèi)星上行鏈路系統(tǒng)。本論文首先分析研究了LTE上行隨機(jī)接入與同步的過程,分析并提出了LTE標(biāo)準(zhǔn)應(yīng)用于低軌衛(wèi)星場景會(huì)產(chǎn)生的問題。設(shè)計(jì)新的前導(dǎo)序列結(jié)構(gòu)以適應(yīng)長時(shí)延的低軌衛(wèi)星環(huán)境,并仿真驗(yàn)證在衛(wèi)星鏈路中新前導(dǎo)序列結(jié)構(gòu)的檢測性能。針對(duì)LTE系統(tǒng)應(yīng)用到低軌衛(wèi)星上時(shí)由于大多普勒頻移帶來的頻率不同步問題,本文分析研究了頻率偏移的估計(jì)算法,并根據(jù)低軌衛(wèi)星的應(yīng)用場景對(duì)整數(shù)頻偏的估計(jì)算法加以改進(jìn),并進(jìn)行仿真驗(yàn)證其估計(jì)性能。最后分析研究傳統(tǒng)的地面LTE系統(tǒng)中的定時(shí)提前量TA問題,提出了適應(yīng)于低軌衛(wèi)星大時(shí)延場景下的定時(shí)提前量策略。同時(shí)針對(duì)衛(wèi)星鏈路下發(fā)射端與接收端存在定時(shí)誤差的問題,采用現(xiàn)有的定時(shí)偏移估計(jì)算法進(jìn)行補(bǔ)償,并對(duì)現(xiàn)有的時(shí)偏估計(jì)算法進(jìn)行改進(jìn),通過仿真驗(yàn)證算法的估計(jì)性能,實(shí)現(xiàn)了低軌衛(wèi)星定時(shí)偏移的估計(jì)與補(bǔ)償,提升了鏈路系統(tǒng)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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN927.23

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