本文選題：航空通信 + LTE��； 參考：《西安電子科技大學》2014年碩士論文

【摘要】：本文首先介紹了航空通信的研究背景和將LTE應(yīng)用到航空通信系統(tǒng)的意義,綜述了多載波通信的抗多普勒技術(shù)和信道估計技術(shù)的研究狀況。作為頻率同步和信道估計技術(shù)研究的前提,準確的信道模型至關(guān)重要,本文介紹了飛行器在巡航階段的信道基本特性,針對不同的飛行仰角,參閱相關(guān)文獻的統(tǒng)計數(shù)據(jù)建立數(shù)學模型。簡要介紹了LTE下行鏈路的物理層標準和相關(guān)協(xié)議,詳細介紹了OFDM技術(shù),并搭建了LTE下行鏈路基帶仿真系統(tǒng)模型,并闡述了將LTE應(yīng)用到航空通信的優(yōu)勢及面臨的問題。在OFDM系統(tǒng)的抗多普勒頻偏技術(shù)研究中,其主要思路是在接收端進行頻偏估計和補償。限于LTE下行可利用的資源有限,現(xiàn)有的算法大都基于循環(huán)前綴或?qū)ьl符號,利用其相關(guān)特征來進行頻偏估計。但是在航空情景下,由于終端移動速度更大,多普勒頻移更大,且受到散射徑的影響,傳統(tǒng)算法的估計性能并不理想。本文建立了受多普勒效應(yīng)影響的信號模型,分析了頻偏和多普勒擴展對系統(tǒng)的影響,仿真分析了現(xiàn)有的一些經(jīng)典估計方案,并針對傳統(tǒng)頻偏估計算法受散射徑影響嚴重的問題,分析了只利用LOS徑估計頻偏的技術(shù),該方案首先需進行時域的信道估計,將直射徑與散射徑分離,仿真表明該方案并不適用于航空場景。利用循環(huán)前綴和導頻進行聯(lián)合估計,由于實現(xiàn)簡單且性能良好被作為最終的方案。針對航空信道快時變的特點,首先分析了傳統(tǒng)LS在不同信道內(nèi)插方案下的系統(tǒng)性能,以及基于基擴展模型的信道估計算法,仿真表明其并不適用于航空場景下,尤其是散射徑延遲比較大時,本文聯(lián)合ICI消除及最強路徑信道估計方案,ICI消除通過求解ICI矩陣重構(gòu)信號,為降低計算復雜性,采用有限長濾波器來實現(xiàn)矩陣求逆運算,最強路徑信道估計方案即在時域抽取能量集中的路徑,其他路徑置零,然后再變換到頻域。該方案能有效地提升了兩徑信道下的系統(tǒng)性能。
[Abstract]:This paper first introduces the research background of aviation communication and the significance of applying LTE to aviation communication system, and summarizes the research status of anti-Doppler technique and channel estimation technology in multi-carrier communication. As the premise of the research of frequency synchronization and channel estimation, accurate channel model is very important. This paper introduces the basic characteristics of the channel in the cruising phase, aiming at different elevation angles. A mathematical model is established by referring to the statistical data in the relevant literature. This paper briefly introduces the physical layer standard and related protocols of LTE downlink, introduces the OFDM technology in detail, builds the simulation system model of LTE downlink baseband, and expounds the advantages and problems of applying LTE to aviation communication. In the research of anti-Doppler frequency offset in OFDM system, the main idea is to estimate and compensate the frequency offset at the receiver. Due to the limited resources available in the downlink of LTE, most of the existing algorithms are based on cyclic prefixes or pilot symbols to estimate the frequency offset. However, in aeronautical scenarios, the estimation performance of the traditional algorithms is not satisfactory because the terminal moves faster, the Doppler frequency shift is larger, and is affected by the scattering path. In this paper, a signal model affected by Doppler effect is established, the influence of frequency offset and Doppler spread on the system is analyzed, some classical estimation schemes are simulated and analyzed, and aiming at the problem that the traditional frequency offset estimation algorithm is seriously affected by scattering path, This paper analyzes the technique of estimating the frequency offset only by using Los path. Firstly, the channel estimation in time domain is carried out, and the direct and scattering paths are separated. The simulation results show that this scheme is not suitable for aviation scenarios. The joint estimation using cyclic prefix and pilot is considered as the final scheme because of its simple implementation and good performance. In view of the fast time-varying characteristics of aviation channel, the system performance of traditional LS under different channel interpolation schemes and the channel estimation algorithm based on base expansion model are analyzed. The simulation results show that the proposed algorithm is not suitable for aviation scenarios. Especially when the scattering path delay is large, the ICI elimination and the strongest path channel estimation scheme are combined in this paper. By solving the ICI matrix to reconstruct the signal, in order to reduce the computational complexity, the finite length filter is used to realize the matrix inversion operation. The strongest path channel estimation scheme is to decimate the energy-concentrated path in time domain, set the other paths to zero, and then transform to frequency domain. This scheme can effectively improve the system performance in two-path channels.
【學位授予單位】：西安電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN929.53

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