本文選題：水聲通信 + 濾波多音調(diào)制��； 參考：《浙江大學》2017年碩士論文

【摘要】：水聲通信作為主要的水下遠距離無線通信方式,在很多領(lǐng)域有著重要的應用。然而水聲通信的研究面臨著很多方面的困難,如:水聲信號隨著信號頻率的增加而衰減;水聲信號在傳播過程中存在著時變的多徑效應;水聲傳播速度較低等。本文針對水聲通信面臨的困難,結(jié)合多載波調(diào)制技術(shù)的特點,描述了一種在無線通信中應用比較廣泛的基于濾波器組的多載波調(diào)制技術(shù),即濾波多音調(diào)制技術(shù)(Filtered-Multitone Modulation,FMT),并且在該調(diào)制技術(shù)下,結(jié)合水聲信道的特性進行水聲信道的估計和均衡。本文首先從理論上推導了 FMT調(diào)制技術(shù)在水聲通信中的可行性,通過仿真分析FMT調(diào)制技術(shù)的特點,其相對于正交頻分復用調(diào)制技術(shù)(Orthogonal Frequency Division Multiplexing,OFDM)技術(shù)的特點是其載波之間不是嚴格的“正交性”,然而其子載波之間有著間隔,子載波之間的干擾幾乎可以忽略,這樣對于抗Doppler有著一定的優(yōu)勢。研究水聲信道的特性是設(shè)計水聲通信系統(tǒng)的基礎(chǔ)。本文從水聲信道的特性出發(fā),介紹了水聲信道中典型的時延Doppler雙擴展特性和稀疏特性,并在此基礎(chǔ)上對水聲信道進行建模分析。通過將幾條主要的到達徑分離來近似表達水聲信道,此外信道的幅度時變和時延時變通過多項式進行擬合的方法來進行表示。本文在此基礎(chǔ)上對水聲信道進行參數(shù)化建模,并將此與FMT調(diào)制技術(shù)進行結(jié)合,進行后續(xù)的信道估計。在得到水聲信道的參數(shù)化模型之后,本文通過該模型下的輸入輸出關(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,并且采用壓縮感知的算法進行簡便求解。本文通過信道的幅度時變和時延時變的特點,提出一種分步估計的方法,該方法結(jié)合信號的前后導頻來估計相應時刻的信道,然后結(jié)合信道建模特性擬合信道的相應參數(shù)來進行信道估計。通過仿真進行對上述方法的驗證。水聲通信中時延擴展引起嚴重的符號間干擾(Inter-SymbolInterference,ISI),特別是在FMT調(diào)制技術(shù)背景下,ISI是不可忽略的,是限制淺海水聲通信性能的一個重要原因。針對這個問題,FMT調(diào)制需要在接收端進行相應的均衡處理。本文主要描述了在FMT調(diào)制技術(shù)下的基于遞歸最小二乘(Recursive Least Squares,RLS)算法的自適應判決反饋(Decision Feedback Equalization,DFE)均衡,并在此基礎(chǔ)上結(jié)合分數(shù)間隔采樣以及基于鎖相環(huán)的Doppler補償方法進行優(yōu)化。此外,本文還提出了一種基于信道估計的均衡,根據(jù)理論推導FMT調(diào)制技術(shù)載波間干擾可忽略的特點,將每一個子載波上符號進行獨立均衡。本文將以上兩種方法進行了仿真分析,驗證其性能的可靠性。最后論文通過海試數(shù)據(jù)進行了 FMT調(diào)制系統(tǒng)的可靠性分析。
[Abstract]:Underwater acoustic communication, as the main underwater long-range wireless communication, has important applications in many fields. However, the research of underwater acoustic communication is faced with many difficulties, such as the attenuation of underwater acoustic signal with the increase of signal frequency, the existence of time-varying multipath effect in the process of underwater acoustic signal propagation, the low speed of underwater acoustic propagation, and so on. In view of the difficulties faced by underwater acoustic communication and the characteristics of multicarrier modulation technology, this paper describes a multi-carrier modulation technology based on filter banks, which is widely used in wireless communication. Filtered-Multitone Modulation / FMT (Filtered-Multitone Modulation / FMT) technique is used to estimate and equalize underwater acoustic channels in combination with the characteristics of underwater acoustic channels. In this paper, the feasibility of FMT modulation technology in underwater acoustic communication is deduced theoretically, and the characteristics of FMT modulation technology are analyzed by simulation. Compared with orthogonal Frequency Division Multiplexing OFDM (OFDM), its characteristic is that its carrier is not strictly orthogonal. However, there is a gap between its subcarriers, and the interference between subcarriers can be almost ignored. In this way, it has a certain advantage in anti-Doppler. Studying the characteristics of underwater acoustic channel is the basis of designing underwater acoustic communication system. Based on the characteristics of underwater acoustic channel, this paper introduces the typical delay Doppler double spread and sparse characteristics in underwater acoustic channel. Based on this, the underwater acoustic channel is modeled and analyzed. Several major paths of arrival are separated to approximate the underwater acoustic channel, in addition, the channel amplitude time-varying and time-delay time-varying are represented by polynomial fitting method. Based on this, the parametric modeling of underwater acoustic channel is carried out, which is combined with FMT modulation technology to carry out subsequent channel estimation. After the parameterized model of underwater acoustic channel is obtained, the high-dimensional channel estimation problem is transformed into a finite dimensional channel parameter estimation problem through the input and output relationship under the model, and the compressed sensing algorithm is used to solve the problem. Based on the characteristics of time-varying amplitude and time-delay, a step by step method is proposed to estimate the channel at the corresponding time by combining the pilot frequency of the signal. Then the channel estimation is carried out by fitting the corresponding parameters of the channel with the channel modeling characteristics. The method is verified by simulation. Inter-Symbol-Interference- ISI (Inter-Symbol-Interference- ISI) caused by delay spread in underwater acoustic communication, especially in the context of FMT modulation technology, can not be ignored and is an important reason for limiting the performance of shallow water acoustic communication. To solve this problem, FMT modulation needs to be equalized at the receiver. This paper mainly describes the adaptive decision feedback (DFE) equalization based on the recursive least squares (RLS) algorithm under FMT modulation, and optimizes the algorithm based on the fractional interval sampling and Doppler compensation based on phase-locked loop (PLL). In addition, an equalization based on channel estimation is proposed. Based on the theoretical derivation of the negligible characteristics of inter-carrier interference (ISI) in FMT modulation technology, the symbols on each subcarrier are equalized independently. In this paper, the two methods are simulated and analyzed to verify the reliability of the performance. Finally, the reliability of FMT modulation system is analyzed by sea test data.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.3

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本文編號：2110588