本文關(guān)鍵詞： 相干光正交頻分復(fù)用 IQ(in phase and quadrature)失衡 載波間干擾(ICI Inter-carrier Interference) 載波頻率偏差　出處：《吉林大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：相干光正交頻分復(fù)用(CO-OFDM)技術(shù)作為光通信的重要技術(shù)之一,憑借其在高速率、長距離通信環(huán)境下仍能取得良好性能的優(yōu)勢,成為近幾年來被廣泛研究和關(guān)注的熱點(diǎn)技術(shù)。傳統(tǒng)的光通信易受色散影響,而OFDM技術(shù)具有較強(qiáng)的抗色散能力,將光通信與OFDM技術(shù)相結(jié)合的CO-OFDM技術(shù)兼?zhèn)淞诉@兩種技術(shù)的優(yōu)勢。隨著通信網(wǎng)絡(luò)的迅速發(fā)展以及通信系統(tǒng)的不斷升級,將CO-OFDM系統(tǒng)廣泛應(yīng)用到實(shí)際中是未來光通信發(fā)展的趨勢,現(xiàn)有許多研究者已經(jīng)通過成果證明這種模式的可行性,但仍有部分問題解決方法仍待完善。CO-OFDM系統(tǒng)采用直接上變頻和直接下變頻結(jié)構(gòu)時(shí),由于發(fā)送端和接收端的硬件器件不理想等因素會引起IQ(in phase and quadrature)失衡問題,IQ失衡指的是I路和Q路的兩路傳輸數(shù)據(jù)無法做到幅度嚴(yán)格相等,相位嚴(yán)格正交。IQ失衡導(dǎo)致在接收端接收到的信號存在載波間干擾,同時(shí),CO-OFDM系統(tǒng)由于收發(fā)端激光器中心頻率偏差也會導(dǎo)致載波頻率偏差,即載波頻偏,而IQ失衡問題與載波頻偏問題又會相互影響,嚴(yán)重影響系統(tǒng)性能,造成信號星座點(diǎn)的發(fā)散、旋轉(zhuǎn)等問題,致使接收到的數(shù)據(jù)在解調(diào)過程中不能準(zhǔn)確的對源信號進(jìn)行恢復(fù),嚴(yán)重劣化系統(tǒng)的性能。本文對CO-OFDM系統(tǒng)中僅存在IQ失衡問題,以及系統(tǒng)存在載波頻偏干擾時(shí)的IQ失衡問題建立解決方案模型,分別提出了相應(yīng)的改進(jìn)算法,并通過Matlab和Optisystem聯(lián)合搭建仿真平臺,對算法進(jìn)行了仿真驗(yàn)證。具體分為以下兩點(diǎn)內(nèi)容:(1)為解決IQ失衡對CO-OFDM系統(tǒng)帶來的載波間干擾問題,并針對Wonzoo Chung*等人提出的基于三個(gè)子集的數(shù)據(jù)輔助類法(本文簡稱W算法)有系統(tǒng)額外開銷的問題,通過數(shù)學(xué)推導(dǎo),在滿足IQ失衡估計(jì)模型所必要的結(jié)構(gòu)基礎(chǔ)上,對傳統(tǒng)數(shù)據(jù)輔助類算法的導(dǎo)頻結(jié)構(gòu)進(jìn)行改進(jìn),將W算法三個(gè)子集的訓(xùn)練序列結(jié)構(gòu)改為兩個(gè)子集(TS,Two Subsets)的改進(jìn)算法,在不增加系統(tǒng)額外開銷的情況下,提高了對IQ失衡因子估計(jì)的準(zhǔn)確性,并通過改進(jìn)算法進(jìn)行IQ失衡補(bǔ)償工作。所提出的TS算法與W算法在使用相同OFDM符號作為訓(xùn)練序列,系統(tǒng)信噪比相同時(shí),TS算法較W算法降低了系統(tǒng)的誤碼率,提高了系統(tǒng)的可靠性。本文通過對W算法和TS算法補(bǔ)償后系統(tǒng)誤碼率隨信噪比變化的仿真驗(yàn)證,在系統(tǒng)發(fā)送端IQ幅度失衡0.7d B,相位失衡25度,傳輸距離240km,且保證誤碼率相同的情況下,TS算法所需要的信噪比值要低于W算法所需要的信噪比值,如在誤碼率為-410時(shí),TS算法所需的信噪比要比W算法低約1d B。(2)為解決CO-OFDM系統(tǒng)中存在載波頻偏干擾時(shí)的IQ失衡問題,借鑒現(xiàn)有經(jīng)典的利用重復(fù)序列結(jié)構(gòu)來進(jìn)行載波同步的方法,把無線OFDM系統(tǒng)中IQ失衡與載波頻偏聯(lián)合補(bǔ)償算法與本文第4章所提出的TS補(bǔ)償算法相結(jié)合,針對CO-OFDM系統(tǒng)提出了改進(jìn)的TS算法,改進(jìn)的TS算法把無線OFDM系統(tǒng)中IQ失衡與載波頻偏聯(lián)合補(bǔ)償算法的三層結(jié)構(gòu)化為兩層結(jié)構(gòu),延續(xù)了TS算法較高的有效性,雖然較TS算法增加了一些系統(tǒng)的額外開銷,但能有效的對載波頻偏與IQ失衡同時(shí)存在的情況對系統(tǒng)進(jìn)行均衡工作。本文通過對W算法和TS算法與改進(jìn)的TS算法補(bǔ)償后系統(tǒng)誤碼率隨信噪比變化的仿真驗(yàn)證,在系統(tǒng)發(fā)送端IQ幅度失衡0.7d B,相位失衡25度,其中歸一化頻偏值fre=0.05,且保證誤碼率相同的情況下,改進(jìn)的TS算法所需要的信噪比值要低于W算法和TS算法所需要的信噪比值,在誤碼率為-410時(shí),改進(jìn)的TS算法所需的信噪比要比TS算法低約5d B,系統(tǒng)的可靠性得到了大幅度的提升,這是由于W算法和TS算法都只考慮系統(tǒng)的IQ失衡,并沒有對系統(tǒng)的載波頻偏進(jìn)行均衡�？梢�,改進(jìn)的TS算法不僅延續(xù)了TS算法可以有效降低系統(tǒng)IQ失衡影響的優(yōu)點(diǎn),又可以降低載波頻偏對系統(tǒng)性能的影響,對IQ失衡和載波頻偏都有較大的容忍度。
[Abstract]:Coherent optical orthogonal frequency division multiplexing (CO-OFDM) technology is one of the most important technology in optical communication, by virtue of its high rate, still has good performance in long distance communication environment advantages, in recent years become hot research and technology is widely concerned. The traditional optical dispersion effect by Xinyi, while OFDM technology has the strong anti dispersion capability, CO-OFDM technology and optical communication and OFDM technology combining the advantages of the two technologies. With the continuous upgrading of the fast development of communication network and communication system, the CO-OFDM system is widely applied to practical optical communication is the future trend of development, the existing achievements by many researchers have proved the feasibility this kind of mode, but there are still some method to solve the problem is to be perfected.CO-OFDM system using the direct conversion and direct conversion structure, the hardware device of the sender and the receiver to ignore To cause (IQ in phase and quadrature) imbalances, imbalance of IQ refers to the transmission data of two I and Q roads do not strictly equal amplitude, phase imbalance strictly orthogonal.IQ signal received at the receiving end the existence of inter carrier interference, at the same time, the CO-OFDM system for laser transmitter and receiver center frequency the deviation will lead to carrier frequency offset, the carrier frequency offset and carrier frequency offset and IQ imbalance problem will influence each other, seriously affect the performance of the system, causing divergence signal constellation, rotation and other issues, resulting in the received data in the demodulation process can not accurately the source signal recovery, serious performance the deterioration of the system. The IQ imbalance exists only in the CO-OFDM system, there is solution model of IQ imbalance of carrier frequency offset interference and system respectively, puts forward the improved algorithm, and through Matlab and Optisystem co simulation platform, the algorithm is verified by simulation. The specific content is divided into the following two points: (1) to solve the interference problem of carrier IQ imbalances on the CO-OFDM system, and based on the Wonzoo proposed by Chung* et al three subset of data based on auxiliary class method (the W algorithm) are the additional system overhead, through mathematical derivation, to meet the IQ imbalance estimation structure basis necessary to model, the pilot structure of traditional data aided algorithm is improved, the training sequence structure W algorithm three subset changed into two subsets (TS, Two, Subsets) of the improved algorithm, without increasing the additional system overhead, improve the accuracy of the estimation of IQ imbalance factor, and IQ imbalance compensation by the improved algorithm. TS algorithm and W algorithm proposed in OFDM using the same symbols as the training sequence, system The signal-to-noise ratio at the same time, the TS algorithm reduces the bit error rate of the system is W algorithm, improve the reliability of the system. Based on the W algorithm and the TS algorithm after the compensation of BER versus SNR changes in system simulation, the sender IQ 0.7d B amplitude imbalance, phase imbalance of 25 degrees, transmission distance 240km, and the error rate under the same signal-to-noise ratio TS algorithm need to signal-to-noise ratio is lower than W algorithm is needed, such as when the bit error rate is -410, the TS algorithm required signal-to-noise ratio is about 1D lower than W algorithm, B. (2) for the partial interference when the imbalance of IQ to solve the problems of carrier frequency in CO-OFDM system, using the existing classic use structure repeat method for carrier synchronization, combining TS compensation algorithm proposed by IQ is imbalance and carrier frequency offset compensation algorithm and the fourth chapter in wireless OFDM system, the CO-OFDM system is proposed. The improved TS The algorithm, the improved TS algorithm to the three layer structure of wireless OFDM system IQ imbalance and carrier frequency offset compensation algorithm of two layer structure, the continuation of the validity of TS is high, although the increase in some additional overhead system than TS algorithm, but can be effective in the carrier frequency offset and IQ imbalance exist at the same time. The situation of equilibrium for the system. The TS algorithm for W compensation algorithm and TS algorithm and improved the BER versus SNR changes in system simulation, the sender IQ 0.7d B amplitude imbalance, phase imbalance of 25 degrees, the normalized frequency offset value fre=0.05, and the error rate under the same circumstances the signal-to-noise ratio, the improved TS algorithm need to signal-to-noise ratio is lower than W algorithm and TS algorithm are needed, in the error rate of -410, TS algorithm improved the SNR required to be lower than the TS algorithm about 5D B, the reliability of the system to a The degree of improvement, this is because the W algorithm and the TS algorithm only considers the system IQ imbalance, and no carrier frequency of the system is balanced. Therefore, the improved TS algorithm is not only the continuation of the TS algorithm can effectively reduce the system advantages of IQ imbalance, but also can reduce the effect of carrier frequency offset on system performance IQ, of imbalance and carrier frequency offset have greater tolerance.

【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】：2017
【分類號】：TN929.1

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