發(fā)布時間：2018-07-01 19:49

  本文選題：水聲通信 + 正交頻分復用　； 參考：《集美大學》2015年碩士論文

【摘要】：實現(xiàn)水下信息傳輸與探測的主要手段是水聲通信。水下唯一可以進行遠距離信息傳輸?shù)奈锢砻劫|(zhì)是水聲信道,不同于無線電信道,水聲信道是一個十分復雜的時空頻變信道,它的主要特征是多變、帶寬有限以及多途效應,因此,水聲通信技術(shù)發(fā)展緩慢。正交頻分復用(Orthogonal Frequency Division Multiplexing,OFDM)由于傳輸速率高、抗多徑能力強、頻譜利用率高等優(yōu)點而在高速無線電通信中得到廣泛應用。但將其應用于水聲通信系統(tǒng)中,OFDM會受到水聲信道的窄頻帶寬和梳狀的幅頻響應特性的影響,不僅沒發(fā)揮其優(yōu)勢,反而對頻偏和相位噪聲非常敏感,使得OFDM的同步問題異常突出。針對這些問題,本文提出了采用對稱三角線性調(diào)頻(Symmetrical Triangular Linear Frequency Modulation,STLFM)信號作為同步碼,基于分數(shù)階Fourier變換(Fractional Fourier Transform,FRFT)的正交多載波水聲通信系統(tǒng)的同步檢測整體方案。通過對STLFM信號在分數(shù)階傅里葉域能量匯聚性的分析發(fā)現(xiàn),一個周期的STLFM信號分別在1p階、2p階處作FRFT,各能產(chǎn)生一次能量尖峰,這大大提高了目標分辨率,為實現(xiàn)同步提供了良好的條件。然后對STLFM信號作為同步碼的系統(tǒng)模型進行了研究,推導了以STLFM信號作為同步碼的聯(lián)合同步算法,以及估計1p階和2p階處的采樣頻差s?f、載波頻差c?f和符號定時0k算法。為了驗證算法的正確性,對基于FRFT-OFDM水聲通信系統(tǒng)進行了仿真實驗和性能分析,以同步誤碼率(Bit Error Rate,BER)作為評價指標,在有噪聲、多徑傳輸和多普勒效應三種環(huán)境組合場景下與傳統(tǒng)OFDM系統(tǒng)采用線性調(diào)頻(Linear Frequency Modulation,LFM)信號作為同步碼進行分析比較;并通過水池實驗驗證了基于FRFT-OFDM水聲通信方案的有效性和可行性,具有一定的應用價值。
[Abstract]:Underwater acoustic communication is the main means of underwater information transmission and detection. The only physical medium that can transmit long-distance information under water is the underwater acoustic channel, which is different from the radio channel. The underwater acoustic channel is a very complex spatio-temporal and frequency-varying channel, which is characterized by variability, limited bandwidth and multipath effect. Therefore, the development of underwater acoustic communication technology is slow. Orthogonal Frequency Division Multiplexing OFDM (OFDM) is widely used in high-speed radio communication due to its high transmission rate, strong anti-multipath ability and high spectral efficiency. However, the application of OFDM in underwater acoustic communication system will be influenced by the narrow bandwidth of underwater acoustic channel and the characteristic of comb-like amplitude-frequency response. It not only does not give full play to its advantages, but also is very sensitive to frequency offset and phase noise, which makes the synchronization problem of OFDM extremely prominent. In order to solve these problems, this paper presents an overall scheme of synchronization detection for orthogonal multi-carrier underwater acoustic communication systems based on Fractional Fourier transform (Fractional Fourier transform) using symmetric triangular Linear Frequency Modulation (STLFM) signals as synchronization codes. By analyzing the energy convergence of STLFM signal in fractional Fourier domain, it is found that a periodic STLFM signal with FRFT at order 1p / 2p can produce a peak of energy, which greatly improves the resolution of the target. It provides a good condition for realizing synchronization. Then, the system model of STLFM signal as synchronization code is studied, and the joint synchronization algorithm using STLFM signal as synchronization code is derived, and the algorithm of estimating sampling frequency difference sf, carrier frequency difference cf and symbol timing 0k at order 1p and 2p are derived. In order to verify the correctness of the algorithm, the simulation experiment and performance analysis of the underwater acoustic communication system based on FRFT-OFDM are carried out. The bit error rate (bit error rate) is used as the evaluation index. Compared with the traditional OFDM system using linear frequency modulation (LFM) signal as synchronization code in the environment of multipath transmission and Doppler effect, the effectiveness and feasibility of the scheme based on FRFT-OFDM underwater acoustic communication are verified by pool experiment. It has certain application value.
【學位授予單位】：集美大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN929.3

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本文編號：2088958