本文選題：衛(wèi)星通信 + OFDM技術(shù)��； 參考：《吉林大學(xué)》2014年碩士論文

【摘要】：寬帶衛(wèi)星通信己成為當(dāng)前通信的新熱點(diǎn)之一，未來的通信是建立在寬帶基礎(chǔ)上的多媒體通信。寬帶衛(wèi)星通信易受下雨等大氣干擾影響，信道特性較差，且頻譜資源緊張。正交頻分復(fù)用(Orthogonal Frequency Division Multiplexing，OFDM)技術(shù)具有抗干擾能力強(qiáng)和頻帶利用率高等特點(diǎn)可以解決上述問題，因而適合應(yīng)用于衛(wèi)星通信系統(tǒng)實(shí)現(xiàn)高速傳輸。但是，OFDM的技術(shù)優(yōu)勢是建立在各子載波正交的基礎(chǔ)上的，對同步誤差極為敏感，衛(wèi)星信道中的多徑效應(yīng)和多普勒頻移都會引起同步偏差，因此本文主要研究衛(wèi)星移動通信系統(tǒng)中OFDM的同步技術(shù)。 本文首先介紹了寬帶衛(wèi)星移動通信信道特點(diǎn)，并提出本文仿真的信道模型。重點(diǎn)分析了多徑效應(yīng)和多普勒頻移，選取郊區(qū)環(huán)境下寬帶衛(wèi)星移動通信信道模型作為本文仿真環(huán)境。而后從OFDM系統(tǒng)的實(shí)現(xiàn)過程出發(fā)，結(jié)合衛(wèi)星信道特性，重點(diǎn)闡述了OFDM系統(tǒng)中同步偏差產(chǎn)生的原因，理論分析并仿真驗(yàn)證了定時偏差和頻率偏差對OFDM系統(tǒng)的影響。采用基于訓(xùn)練序列的方法研究OFDM同步技術(shù)，首先進(jìn)行定時同步，分析并在郊區(qū)環(huán)境衛(wèi)星信道下仿真了SchmidlCox方法和Minn方法的原理和性能，在此基礎(chǔ)上改進(jìn)訓(xùn)練序列結(jié)構(gòu)，利用其共軛對稱性質(zhì)實(shí)現(xiàn)定時估計(jì)，定時峰值尖銳，使定時同步精度有了很大提高。頻率同步分為小數(shù)頻偏估計(jì)和整數(shù)頻偏估計(jì)兩個過程，一般先進(jìn)行小數(shù)頻偏估計(jì)，，而后進(jìn)行校正消除ICI，再進(jìn)行整數(shù)頻偏估計(jì)。 本文深入研究了SchmidlCox的頻率同步算法，并基于該算法提出了一種進(jìn)行多次估值取平均的小數(shù)頻偏校正方法，其估計(jì)性能更準(zhǔn)確。對Minn算法進(jìn)行了研究和性能仿真。對Moose算法和基于導(dǎo)頻序列的算法中參數(shù)對同步性能的影響進(jìn)行分析和仿真，基于SchmidlCox整數(shù)頻偏估計(jì)算法的改進(jìn)思想，給出由Moose算法而來的一種整數(shù)頻偏估計(jì)的改進(jìn)算法。最后，根據(jù)定時同步所采用的訓(xùn)練符號結(jié)構(gòu)，提出了基于共軛關(guān)系的小數(shù)頻偏估計(jì)方法和新的整數(shù)頻偏估計(jì)方法，對接收端解調(diào)信號誤碼率進(jìn)行仿真，該算法頻率同步性能與Minn算法基本一致。
[Abstract]:Broadband satellite communication has become one of the new hotspots in current communication. The future communication is multimedia communication based on broadband. Wideband satellite communications are vulnerable to atmospheric interference such as rain, so the channel characteristics are poor, and the spectrum resources are scarce. The orthogonal Frequency Division Multiplexing OFDM (OFDM) technology can solve the above problems because of its strong anti-jamming ability and high frequency band efficiency, so it is suitable for high speed transmission in satellite communication systems. However, the advantages of OFDM are based on the orthogonal subcarriers, which are sensitive to synchronization errors. The multipath effect and Doppler frequency shift in satellite channels will cause synchronization errors. Therefore, this paper mainly studies the synchronization technology of OFDM in satellite mobile communication system. In this paper, the characteristics of wideband satellite mobile communication channel are introduced, and the channel model simulated in this paper is presented. The multipath effect and Doppler shift are analyzed, and the channel model of wideband satellite mobile communication in suburban environment is selected as the simulation environment. Based on the realization process of OFDM system and the characteristics of satellite channel, the causes of synchronization bias in OFDM system are discussed, and the effects of timing error and frequency deviation on OFDM system are analyzed and verified by simulation. The OFDM synchronization technology is studied based on training sequence. Firstly, timing synchronization is carried out. The principle and performance of SchmidlCox method and Minn method are analyzed and simulated in suburban environment satellite channel, and the structure of training sequence is improved. The timing estimation is realized by using its conjugate symmetry property, and the timing peak is sharp, so the precision of timing synchronization is greatly improved. Frequency synchronization is divided into two processes: fractional frequency offset estimation and integer frequency offset estimation. Generally, the fractional frequency offset estimation is carried out first, then the ICI is corrected and the integer frequency offset estimation is carried out. In this paper, SchmidlCox's frequency synchronization algorithm is studied in depth, and based on this algorithm, a new method of decimal frequency offset correction based on multiple estimations is proposed. The estimation performance is more accurate. Minn algorithm is studied and simulated. The effect of parameters on synchronization performance in Moose algorithm and pilot sequence based algorithm is analyzed and simulated. Based on the improved SchmidlCox integer frequency offset estimation algorithm, an improved integer frequency offset estimation algorithm based on Moose algorithm is presented. Finally, according to the training symbol structure used in timing synchronization, a new integer frequency offset estimation method and a new integer frequency offset estimation method based on conjugate relation are proposed, and the bit error rate of demodulated signal at the receiver is simulated. The frequency synchronization performance of this algorithm is basically consistent with that of Minn algorithm.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN927.2

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