本文選題：時變信道 + 語音通信��； 參考：《廈門大學》2014年碩士論文

【摘要】：21世紀以來,人類開發(fā)利用海洋的步伐越來越快,人類對海洋信息傳輸?shù)男枨蟠蟠笤黾?水聲語音通信研究也越來越受到人類的重視。然而陸上的無線電語音通信技術并不適于水聲語音通信,因為聲波是水下唯一能進行遠距離傳輸?shù)哪芰啃问?而水聲信道的隨機時-空-頻變、窄帶高噪、多途效應及多普勒頻移等特性給高速、穩(wěn)健的水聲語音通信帶來了極大的挑戰(zhàn)。 正交頻分復用(OFDM, Orthogonal Frequency Division Multiplexing)技術作為一種多載波調(diào)制技術,由于其高頻譜利用率、強抗多徑性能成為近年來人們研究的熱點。然而,在多徑時延大、多普勒頻移嚴重的時變水聲信道中,OFDM子載波間的正交性易遭到破壞,導致OFDM通信性能下降。時間反轉技術(TRM,Time Reversal Mirror)具有空時聚焦特性,可在無環(huán)境先驗知識的情況下實現(xiàn)信道匹配,提高信噪比。然而時反處理同樣面臨著時變信道下性能下降的問題。時頻二維差分檢測無需載波恢復,抗干擾能力強,能夠抵抗數(shù)據(jù)塊內(nèi)的時變影響。 考慮到以上幾點,為了抵抗信道時變特性的影響,結合OFDM通信、時間反轉及時頻二維差分的優(yōu)點,本文進行時反差分OFDM水聲語音通信技術研究,并在DSP平臺上進行該系統(tǒng)OFDM調(diào)制解調(diào)部分的設計實現(xiàn)。 本文的主要工作如下： 1.介紹了OFDM及時間反轉基本原理,分析了信道時變特性對OFDM通信及時間反轉的影響,確定采用基于探針更新的時反處理應用于OFDM通信方案。 2.介紹了時頻二維差分基本原理,研究了時頻二維差分調(diào)制在OFDM水聲語音通信中的應用,給出了時反差分OFDM水聲語音通信基本模型,分析了其抗信道多徑及時變性能。在時變信道下進行了仿真實驗,實驗表明,基于探針更新的時反差分OFDM方案能夠較好地抵抗信道時變特性對水聲語音通信的影響。 3.在上述工作的基礎上,通過海試實驗驗證了時反差分OFDM水聲語音通信在時變信道下的優(yōu)越性,并基于DSP進行OFDM調(diào)制解調(diào)實時實現(xiàn)研究。
[Abstract]:Since the 21st century, the pace of human exploitation and utilization of the ocean has become more and more rapid, the demand for ocean information transmission has increased greatly, and the research of underwater acoustic voice communication has been paid more and more attention by human beings. However, land-based radio voice communication technology is not suitable for underwater acoustic communication, because acoustic wave is the only form of energy that can be transmitted remotely under water, and the random time-space-frequency variation of underwater acoustic channel, narrow band high noise, The characteristics of multipath effect and Doppler shift bring great challenges to the high speed and robust underwater acoustic communication. As a kind of multicarrier modulation technology, Orthogonal Frequency Division Multiplexing (OFDM) technology has become a hot topic in recent years because of its high spectral efficiency. However, in time-varying underwater acoustic channels with large multipath delay and severe Doppler frequency shift, the orthogonality between subcarriers is easily destroyed, which leads to the deterioration of OFDM communication performance. The time reversal technique (TRM / time Reversal mirror) has the property of space-time focusing, which can realize channel matching and improve signal-to-noise ratio (SNR) without prior knowledge of environment. However, time-back processing also faces the problem of performance degradation in time-varying channels. Time-frequency 2-D differential detection does not need carrier recovery and has strong anti-interference ability and can resist the time-varying influence in the data block. Considering the above points, in order to resist the influence of the time-varying characteristics of the channel, combined with the advantages of OFDM communication and time-reversal time-frequency two-dimensional difference, this paper studies the time-contrast division OFDM underwater acoustic communication technology. The OFDM modulation and demodulation part of the system is designed and implemented on the DSP platform. The main work of this paper is as follows: 1. This paper introduces the basic principle of OFDM and time reversal, analyzes the influence of channel time-varying characteristics on OFDM communication and time reversal, and determines that the time-back processing based on probe updating is applied to OFDM communication scheme. 2. This paper introduces the basic principle of time-frequency two-dimensional difference, studies the application of time-frequency two-dimensional differential modulation in OFDM underwater acoustic speech communication, presents the basic model of time-contrast-division OFDM underwater acoustic communication, and analyzes its anti-channel multipath and time-varying performance. Simulation experiments in time-varying channels show that the time-varying OFDM scheme based on probe updating can better resist the influence of time-varying channel characteristics on underwater acoustic speech communication. 3. On the basis of the above work, the superiority of time-contrast OFDM underwater acoustic communication in time-varying channel is verified by sea trial experiment, and the real-time realization of OFDM modulation and demodulation based on DSP is studied.
【學位授予單位】：廈門大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN929.3

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