本文關(guān)鍵詞： 單載波頻域均衡 短波 特殊字 判決反饋 迭代塊判決反饋均衡　出處：《中國艦船研究院》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：短波通信在軍事通信領(lǐng)域有著重要地位，是軍事通信的主要方式之一。但是由于受到傳輸信道的影響，信號在接收端會產(chǎn)生嚴(yán)重的符號間干擾（Inter-Symbol Interference，ISI），從而影響系統(tǒng)性能。為了減小ISI的影響，通常采用正交頻分復(fù)用（OrthogonalFrequency Division Multiplexing，OFDM）技術(shù)和單載波時域均衡（Single Carrier TimeDomain Equalization，SC-TDE）技術(shù)。但OFDM技術(shù)存在很高的峰均比（Peak-to-AveragePower Ratio，PAPR），并且對頻率偏移和相位噪聲十分敏感，SC-TDE的復(fù)雜度又隨著時延擴(kuò)展長度的增加變得難以接受。鑒于此，論文將單載波頻域均衡（Single CarrierFrequency Domain Equalization，SC-FDE）技術(shù)作為研究對象。 論文首先對短波通信及其寬帶化作了簡要介紹，，分析了短波信道的傳輸特性和兩種常用的建模方法：窄帶Watterson模型和寬帶ITS模型。 其次，論文分析了單載波頻域均衡的基本原理，包括其系統(tǒng)框圖和數(shù)學(xué)模型。同時介紹了單載波頻域均衡系統(tǒng)中一種常用的幀格式和用作循環(huán)前綴的特殊字（UniqueWord，UW）序列。詳細(xì)分析了特殊字序列的類型和產(chǎn)生方式，并對特殊字序列的包絡(luò)、自相關(guān)函數(shù)和幅頻特性進(jìn)行了證明。 然后，論文從理論上對單載波頻域均衡系統(tǒng)和正交頻分復(fù)用系統(tǒng)的峰均比、信道容量、誤碼性能以及對頻率偏移和相位噪聲的敏感度進(jìn)行了詳細(xì)分析和比較。 接下來，論文重點分析了單載波頻域均衡系統(tǒng)中的頻域均衡算法，并分別進(jìn)行了推導(dǎo)和仿真。常用的線性均衡算法有迫零（Zero Forcing，ZF）均衡和最小均方誤差（Minimum Mean Square Error，MMSE）均衡。另外還有最小二乘（Least Square，LS）均衡，其缺點是需要多個訓(xùn)練序列，這大大降低了數(shù)據(jù)傳輸效率，因此并不常用。針對頻域存在零點的信道，存在一類特殊字輔助的線性均衡算法，通過將特殊字序列和數(shù)據(jù)序列分開處理，能夠有效緩解由此帶來的性能惡化。 為了進(jìn)一步抑制噪聲干擾和符號間干擾，混合判決反饋均衡（Hybrid DecisionFeedback Equalization，H-DFE）被提出。與之等價的還有一種被稱為噪聲預(yù)測判決反饋均衡（Noise Prediction Decision Feedback Equalization，NP-DFE）的結(jié)構(gòu)，所不同的是噪聲預(yù)測判決反饋均衡的前饋與反饋部分互相獨立。殘留符號間干擾消除（ResidualInter-Symbol Interference Cancellation，RISIC）算法也是一種判決反饋算法，它避免了矩陣求逆運算。 最后，論文詳細(xì)闡述了單載波頻域均衡系統(tǒng)中的迭代塊判決反饋均衡（IterativeBlock Decision Feedback Equalization, IBDFE）算法。這種算法的前饋和反饋部分均在頻域進(jìn)行，采用反饋加迭代的方式大幅提升了系統(tǒng)性能，但是其復(fù)雜度很高。雖然通過參數(shù)近似可以適當(dāng)降低其復(fù)雜度，但這種近似存在參數(shù)模糊性，其性能很不穩(wěn)定。為此，論文在IBDFE結(jié)構(gòu)的基礎(chǔ)上，利用最小均方誤差準(zhǔn)則，通過推導(dǎo)提出了一種新的簡化算法，并進(jìn)一步推導(dǎo)出了其噪聲預(yù)測結(jié)構(gòu)的等價形式。之后對現(xiàn)有低復(fù)雜度算法和所提出簡化算法的均方誤差（Mean Square Error，MSE）性能進(jìn)行了理論分析，并對IBDFE結(jié)構(gòu)下各種均衡算法的計算復(fù)雜度進(jìn)行了比較。結(jié)果顯示，所提出的簡化算法大大降低了計算復(fù)雜度，同時，誤碼性能的仿真表明，所提出的簡化算法在誤碼率方面相比傳統(tǒng)算法有一定減損。
[Abstract]:Shortwave communication plays an important role in the field of military communication, is one of the main ways of military communication. But due to the impact of the transmission channel, the signal generated serious inter symbol interference at the receiving end will (Inter-Symbol Interference, ISI), which affects the performance of the system. In order to reduce the influence of ISI, usually using orthogonal frequency division multiplexing (OrthogonalFrequency Division Multiplexing, OFDM) technology and single carrier time domain equalization (Single Carrier TimeDomain Equalization, SC-TDE). But OFDM technology has very high peak to average ratio (Peak-to-AveragePower, Ratio, PAPR), and is very sensitive to frequency offset and phase noise, the complexity of the SC-TDE and with the increase of the length of delay spread is not accepted in view. In this paper, the single carrier frequency domain equalization (Single CarrierFrequency Domain Equalization, SC-FDE) technology as the research object.
This paper briefly introduces shortwave communication and broadband technology, analyzes the transmission characteristics of HF channel and two commonly used modeling methods: narrow band Watterson model and broadband ITS model.
Secondly, this paper analyzes the basic principle of the single carrier frequency domain equalization, including its system diagram and mathematical model. At the same time introduces a common frame format in single carrier frequency domain equalization system and used as a special word cyclic prefix (UniqueWord, UW) sequence. A detailed analysis of the special type of word sequence and generating, and envelope the special word sequence, autocorrelation function and amplitude frequency characteristic are proved.
Then, the paper theoretically analyzes and compares the peak to average power ratio, channel capacity, BER performance and sensitivity to frequency offset and phase noise of single carrier frequency domain equalization system and orthogonal frequency division multiplexing system.
Next, this paper focuses on the analysis of frequency domain equalization in single carrier frequency domain equalization system, and respectively are deduced and simulated. The linear equalization algorithm commonly used with zero forcing (Zero Forcing, ZF) equilibrium and minimum mean square error (Minimum Mean Square Error, MMSE). In addition to the least squares equalization (Least Square, LS) equilibrium, the disadvantages of the requirement of a training sequence, which greatly reduces the data transmission efficiency, so it is not commonly used. Based on frequency domain channel are zero, there is a linear equalization algorithm for a class of special auxiliary word, the special word sequences and data sequences separately, can effectively alleviate the performance degradation of the resulting.
In order to suppress the noise interference and intersymbol interference further, hybrid decision feedback equalization (Hybrid DecisionFeedback Equalization, H-DFE) is proposed. The equivalent one is known as the noise prediction decision feedback equalization (Noise Prediction Decision Feedback Equalization, NP-DFE) structure, which is different in the noise prediction decision feedback equalization of feedforward and feedback some are independent of each other. The residual inter symbol interference cancellation (ResidualInter-Symbol Interference Cancellation RISIC) algorithm is a kind of decision feedback algorithm, it avoids the computation of matrix inversion.
Finally, the paper elaborates on the iterative block decision in SC-FDE system (IterativeBlock Decision Feedback Equalization feedback equalization, IBDFE) algorithm. This algorithm feedforward and feedback part in the frequency domain, using feedback and iterative way greatly improves the system performance, but its complexity is very high. Although the parameter approximation may be appropriate to reduce its complexity, but the approximate parameters are fuzzy, the performance is very unstable. Therefore, based on the IBDFE structure, using the minimum mean square error criterion is proposed by a new simplified algorithm is deduced to predict the structure of equivalent form of noise. The mean square error of the existing low complexity of the proposed algorithm and simplified algorithm (Mean Square Error, MSE) performance of the theoretical analysis and calculation of various equalization algorithm under IBDFE structure The complexity is compared. The results show that the proposed algorithm greatly reduces the computational complexity. Meanwhile, the simulation of BER performance shows that the simplified algorithm has a certain reduction in bit error rate compared with the traditional algorithm.

【學(xué)位授予單位】：中國艦船研究院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN925

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