本文選題：水聲通信 + 信道估計�。� 參考：《浙江大學(xué)》2014年博士論文

【摘要】：水聲通信是水下環(huán)境中實現(xiàn)無線傳輸?shù)闹饕侄�。水中聲傳播受三個主要因素制約：隨信號頻率增大的衰減,時變的傳播多徑以及較慢的傳播速度。水聲傳播的物理特性造成水聲信道,特別是淺海聲信道可用帶寬窄,時延和多普勒擴展較大且隨環(huán)境變化而變化,使得水聲通信面臨許多陸地?zé)o線電通信中不曾遇到的技術(shù)難點。 論文針對淺海時變水聲信道下的可靠通信問題,開展水聲通信信道估計-信道均衡技術(shù)的聯(lián)合研究。論文挖掘信道的稀疏特性,采用壓縮傳感算法估計稀疏信道,提高信道估計性能的同時降低算法的復(fù)雜度。引入時反處理和頻域上與之對偶的頻反處理簡化信道均衡過程。此外,論文將對信道估計和均衡問題的研究由單入單出(Single-Input Single-Output-SISO)通信系統(tǒng)擴展到多入多出(Multiple-Input Multiple-Output-MIMO)通信系統(tǒng)。在理論算法研究的基礎(chǔ)上,還進行了通信實驗系統(tǒng)設(shè)計并在多次湖海試驗中得到使用；進而通過實驗數(shù)據(jù)處理分析,驗證了論文方案的有效性及實際性能。 信道特性的研究是分析和設(shè)計水聲通信系統(tǒng)的基礎(chǔ)。論文針對淺海水聲通信信道時延多普勒雙擴展的特性對信道進行建模。首先利用水聲信道的稀疏特性,用幾條主要的分離路徑近似表示信道,然后用多項式分別擬合各到達(dá)路徑的幅度時變和時延時變,并以這些參數(shù)化表示為基礎(chǔ),推導(dǎo)出描述通信信道輸入輸出關(guān)系的數(shù)學(xué)模型。與之前描述時延多普勒雙擴展特性的信道模型相比,本論文推導(dǎo)的路徑時變參數(shù)化模型考慮了路徑幅度的時變及由時延變化引起的成型脈沖上采樣點的偏移這些被其它模型忽視的問題,能夠更好地近似實際信道的時變特性。 路徑時變參數(shù)化模型用有限的參數(shù)描述通信信道輸入輸出關(guān)系,將高維的信道估計問題轉(zhuǎn)化為有限維度的信道參數(shù)估計問題,并可采用壓縮傳感算法求解。注意到重采樣和載波頻移補償后的等效信道時變慢的特點,論文提出了一種分步估計時延和多普勒的信道估計方法,該方法使參數(shù)的搜索范圍從二維時延-多普勒平面退化到一維時延／多普勒區(qū)間,減少了字典的維數(shù),從而可降低計算復(fù)雜度和存儲空間需求。同時,相比于時延和多普勒同步估計方法,將時延和多普勒分開估計又有效避免了參數(shù)間的耦合,可以得到更精確的信道估計結(jié)果。仿真和實驗數(shù)據(jù)處理結(jié)果驗證了時延多普勒分步估計方法的性能。 淺海水聲信道中時延擴展引起嚴(yán)重的碼間干擾(Inter-Symbol Interference-ISI),是限制淺海水聲通信性能的重要原因之一。針對這一問題,論文研究了水聲通信中的信道均衡技術(shù)。時間反轉(zhuǎn)處理利用環(huán)境本身壓縮時域上擴展的信號,是一種利用環(huán)境物理特性實現(xiàn)通信信號處理的方法。時反處理并無法完全消除ISI,但是將時反處理和信道均衡結(jié)合可以在很大程度上簡化均衡器的設(shè)計。論文將基于路徑時變參數(shù)化模型的時變信道響應(yīng)估計應(yīng)用于時反處理,把基于信道時不變假設(shè)的傳統(tǒng)時反通信推廣到時變信道。此外,論文還提出了頻域上與時間反轉(zhuǎn)對偶的頻率反轉(zhuǎn)概念。頻反處理可以壓縮多普勒效應(yīng)引起的信號頻率擴展以消除正交頻分復(fù)用(Orthogonal Frequency Division Multiplexing-OFDM)通信中的載波間干擾(Inter-Carrier Interference-ICI)。 論文進一步研究了MIMO水聲通信系統(tǒng)中的信道估計與均衡問題。論文將路徑時變參數(shù)化模型擴展到MIMO信道,然后由此模型推導(dǎo)出離散時間MIMO信道輸入輸出關(guān)系,并將時延多普勒分步估計方法推廣到對MIMO水聲通信信道的估計中。在對MIMO水聲通信信道均衡的研究中,論文將MIMO體制與時反技術(shù)結(jié)合,利用時反的空間聚焦特性實現(xiàn)與多個用戶的同時通信;將SISO水聲通信系統(tǒng)中的判決反饋均衡器(Decision Feedback Equalizer-DFE)擴展到MIMO系統(tǒng)中,在反饋部分引入其它路的發(fā)射符號在消除ISI的同時消除信道間干擾(Cochannel Interference-CCI)。論文還將頻反頻域均衡方法擴展到MIMO通信中,與時反處理一樣,頻反處理也能達(dá)到空間聚焦的效果,消除CCI,是MIMO-OFDM中一種潛在有效的頻域均衡手段。
[Abstract]:Underwater acoustic communication is the main means to realize wireless transmission in underwater environment. Acoustic propagation in water is restricted by three main factors: attenuation with signal frequency, time-varying propagation multipath and slower propagation speed. The physical characteristics of underwater acoustic propagation cause underwater acoustic channel, especially in shallow sea sound channel with narrow bandwidth, delay and Doppler expansion. Large and changing with the environment, underwater acoustic communication is faced with many technical difficulties that have not been encountered in terrestrial radio communications.
In this paper, a joint study of channel estimation - channel equalization in underwater acoustic channel is carried out in light of the time-varying underwater acoustic channel. The paper excavate the sparse characteristics of the channel and estimate the sparse channel using the compression sensing algorithm to improve the performance of the channel estimation while reducing the complexity of the algorithm. The dual frequency inverse processing simplifies the channel equalization process. In addition, this paper extends the study of channel estimation and equalization from single out single out (Single-Input Single-Output-SISO) communication system to multiple entry and multiple (Multiple-Input Multiple-Output-MIMO) communication system. Based on the study of theoretical calculation, the communication experiment system is also set up. It has been used in many experiments of lake and sea. The validity and practical performance of the scheme are verified by experimental data processing and analysis.
The research of channel characteristics is the basis of analysis and design of underwater acoustic communication system. In this paper, the channel is modeled by the characteristics of channel delay Doppler double extension in shallow sea acoustic communication channel. Firstly, the sparse characteristic of underwater acoustic channel is used to approximate the channel with several main separation paths, and then the amplitude of each arrival path is fitted by polynomial respectively. On the basis of these parameterized representations, the mathematical model describing the input and output relations of communication channels is derived. Compared with the channel model describing the doubly extended characteristic of time delay Doppler, the time-varying parameterized model derived from this paper takes into account the time variation of the path amplitude and the formation caused by the change of time delay. The offset of the upper sampling points of the pulse, which is ignored by other models, can better approximate the time-varying characteristics of the actual channel.
The path time-varying parameterized model describes the input and output relation of communication channel with limited parameters, and transforms the high dimension channel estimation into the finite dimension channel parameter estimation problem, and can use the compression sensing algorithm to solve the problem. Step estimation time delay and Doppler's channel estimation method, which reduces the search range from two-dimensional delay to Doppler plane to one dimension time delay / Doppler interval, reduces the dimension of the dictionary and reduces the computational complexity and storage space. At the same time, the time delay and the Doppler synchronization method are compared. The split estimation can effectively avoid the coupling between parameters and obtain more accurate channel estimation results. The simulation and experimental data processing results verify the performance of the time-delay Doppler step estimation method.
Time delay expansion in shallow sea underwater acoustic channel causes serious inter code interference (Inter-Symbol Interference-ISI), which is one of the important reasons for limiting the performance of shallow sea acoustic communication. The communication signal processing method is realized by the environmental physical properties. The time inverse processing can not completely eliminate the ISI, but the combination of time reversal and channel equalization can simplify the design of equalizer to a large extent. In addition, the frequency reversal concept of frequency reversal in frequency domain with time reversal is also proposed. Frequency inverse processing can compress the signal frequency expansion caused by the Doppler effect to eliminate intercarrier interference in Orthogonal Frequency Division Multiplexing-OFDM communication (Int Er-Carrier Interference-ICI).
The paper further studies the channel estimation and equalization in MIMO underwater acoustic communication system. This paper extends the path time-varying parameterized model to the MIMO channel, and then derives the input and output relation of the discrete time MIMO channel, and extends the time-delay Doppler step estimation method to the estimation of the MIMO underwater communication channel. In the MIM In the study of channel equalization for O underwater acoustic communication, the paper combines the MIMO system with the time inverse technology and uses the time inverse spatial focusing characteristics to realize the simultaneous communication with multiple users. The decision feedback equalizer (Decision Feedback Equalizer-DFE) in the SISO underwater acoustic communication system is extended to the MIMO system, and the other channel emitter is introduced in the feedback part. ISI eliminates inter channel interference (Cochannel Interference-CCI) at the same time. This paper also extends the frequency inverse frequency domain equalization method to MIMO communication. As with time reversal processing, frequency inverse processing can also achieve the effect of space focusing and eliminate CCI. It is a potentially effective frequency domain equalization method in MIMO-OFDM.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN929.3

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