时变信道下的时反OFDM水声语音通信技术研究

发布时间：2018-05-01 15:34

本文选题：时变信道 + 语音通信　；参考：《厦门大学》2014年硕士论文

【摘要】：21世纪以来,人类开发利用海洋的步伐越来越快,人类对海洋信息传输的需求大大增加,水声语音通信研究也越来越受到人类的重视。然而陆上的无线电语音通信技术并不适于水声语音通信,因为声波是水下唯一能进行远距离传输的能量形式,而水声信道的随机时-空-频变、窄带高噪、多途效应及多普勒频移等特性给高速、稳健的水声语音通信带来了极大的挑战。正交频分复用(OFDM, Orthogonal Frequency Division Multiplexing)技术作为一种多载波调制技术,由于其高频谱利用率、强抗多径性能成为近年来人们研究的热点。然而,在多径时延大、多普勒频移严重的时变水声信道中,OFDM子载波间的正交性易遭到破坏,导致OFDM通信性能下降。时间反转技术(TRM,Time Reversal Mirror)具有空时聚焦特性,可在无环境先验知识的情况下实现信道匹配,提高信噪比。然而时反处理同样面临着时变信道下性能下降的问题。时频二维差分检测无需载波恢复,抗干扰能力强,能够抵抗数据块内的时变影响。考虑到以上几点,为了抵抗信道时变特性的影响,结合OFDM通信、时间反转及时频二维差分的优点,本文进行时反差分OFDM水声语音通信技术研究,并在DSP平台上进行该系统OFDM调制解调部分的设计实现。本文的主要工作如下： 1.介绍了OFDM及时间反转基本原理,分析了信道时变特性对OFDM通信及时间反转的影响,确定采用基于探针更新的时反处理应用于OFDM通信方案。 2.介绍了时频二维差分基本原理,研究了时频二维差分调制在OFDM水声语音通信中的应用,给出了时反差分OFDM水声语音通信基本模型,分析了其抗信道多径及时变性能。在时变信道下进行了仿真实验,实验表明,基于探针更新的时反差分OFDM方案能够较好地抵抗信道时变特性对水声语音通信的影响。 3.在上述工作的基础上,通过海试实验验证了时反差分OFDM水声语音通信在时变信道下的优越性,并基于DSP进行OFDM调制解调实时实现研究。
[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.
【学位授予单位】：厦门大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.3

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