多输入多输出被动时反水声通信技术研究

发布时间：2018-07-15 18:56

【摘要】：近年来,人们在浅水领域从事的海洋活动日益增多,愈来愈关注和重视水声通信技术,对水声通信的速率和性能提出了更高的要求。多输入多输出(Multiple-input multiple-output,MIMO)技术可以利用浅水环境中不同收发阵元间水声信道的空间弱相关性来取获取丰富的空间自由度,因此可以提高水声通信的速率和通信性能。时反技术(Time reversal,TR)计算复杂度低,并且其具有的良好的空时聚焦特性可以降低浅水信道的多途效应所导致的码间干扰(Inter-symbol interference,ISI)以及空间相关性所导致的同道干扰(Co-channel interference,CCI),因此可以使通信系统以较低的复杂度获得良好的通信性能。按空时聚焦实现过程的不同,TR技术分为主动时反(Active time reversal,ATR)和被动时反(Passive time reversal,PTR)。与ATR相比,PTR的实现过程中探测信号与信息信号之间的时间间隔更短,更能保证估计的信道和实际传输信道的一致性,因此PTR更适用于实际的浅水环境。面对高速、高性能水声通信的需求,对MIMO-PTR水声通信技术进行研究具有重要的理论和实际意义。本文基于MIMO-PTR水声通信的研究现状和发展趋势,并结合MIMO技术和PTR技术的特点,重点对MIMO-PTR水声通信中PTR处理后残余的ISI和CCI抑制方法进行了详细的研究。通过理论推导、仿真分析和试验验证来证明所研究方法的有效性。论文主要围绕以下几个方面展开研究。1、研究水声通信中PTR的干扰抑制性能。PTR的空时聚焦性能可以压缩水声信道的多途效应,降低不同发射阵元所发射的信息信号对应的传输信道的空间相关性,进而达到降低ISI和CCI并且提高通信性能效果。PTR的干扰抑制性能直接决定了残余的ISI和CCI多少,进而决定了用于后处理的其他技术的复杂度。现有的PTR水声通信的研究主要分为两个方面:单输入多输出(Single-input multiple-output,SIMO)PTR水声通信和同时利用空间分集和空分复用的MIMO-PTR水声通信。因此,基于PTR水声通信的研究现状,对PTR的干扰抑制性能进行分析。首先通过理论推导,得出衡量PTR的干扰抑制性能的技术指标——信号干扰噪声比的一般表达式,然后基于射线声学理论和信道的几何结构建立了浅海信道模型,并以此为基础分析了接收阵元数、发射阵元数以及符号信噪比等因素对PTR的干扰抑制性能的影响。结果表明,无论是在SIMO-PTR水声通信还是同时利用空间分集和空分复用的MIMO-PTR水声通信中,PTR处理后都会存在残余的干扰。此时,要进一步提高通信性能,需要使用自适应均衡以及自适应干扰抵消等技术进行后处理。2、研究基于时反空时分组编码(Time-reversal space-time block coding,TR-STBC)的MIMO-PTR水声通信方法。PTR水声通信中,PTR的干扰抑制性能与空间分集增益有关。当接收阵元数较少时,现有的SIMO-PTR水声通信方法仅通过接收分集,获得的空间分集增益低,因此PTR的抑制性能较差并且PTR后处理的自适应均衡的复杂度较高。为了利用发射分集进一步提高PTR的干扰抑制性能,论文提出了基于TR-STBC的MIMO-PTR水声通信方法。所提方法基于适用于频率选择性信道的2元发射的TR-STBC方案的原理以及适用于任何发射阵元的1/2码率的STBC方案的原理,设计了适用于任何发射阵元的1/2码率的TR-STBC方案,并将该TR-STBC方案与PTR相结合应用于水声通信中。论文分析了所提方法的原理,并对所提方法的有效性进行了仿真分析和试验验证。结果表明,所提方法额外利用发射分集提高了 PTR的干扰抑制性能,因此与SIMO-PTR水声通信方法相比,所提方法后处理所用的自适应均衡的复杂度更低并且PTR处理后的性能更优。3、研究连续ISI和CCI抵消的MIMO-PTR水声通信方法同时利用空间分集和空分复用的MIMO-PTR水声通信虽然可以通过PTR的空时聚焦有效地抑制水声通信中的ISI和CCI,但是PTR处理后的信号中仍然存在残余的ISI和CCI,这会影响通信的性能。为了以更低的运算复杂度抑制PTR处理后残余的ISI和CCI,基于连续干扰抵消(Successive interference cancellation,SIC)技术的设计原理和PTR处理后的组合信道响应的特点,提出了连续ISI和CCI抵消的MIMO-PTR水声通信方法。首先分析了所提方法的原理,然后利用信道水池和吉林省松花湖试验获得的试验数据,对所提方法在实际水下环境中的有效性进行了验证。理论分析和试验结果表明,所提方法可以有效抑制PTR处理后的残余干扰,因此与未使用任何技术进行后处理的MIMO-PTR水声通信相比,所提方法的通信性能更优;与现有的基于SIC的MIMO-PTR水声通信方法相比,在通信性能相近的情况下,所提方法的运算复杂度更低。4、研究滤波多音(Filtered multitone,FMT)调制的MIMO-PTR水声通信方法。当通信带宽较宽时,同时利用空间分集和空分复用的MIMO-PTR水声通信若使用单载波调制(Single-carrier,SC)技术,则PTR处理后的残余干扰影响的码元范围会比较大,这会导致PTR处理后的性能较差并且后处理所用的干扰抑制技术较为复杂。针对这一问题,基于FMT技术的特点,提出了 FMT调制的MIMO-PTR水声通信方法。所提方法利用FMT技术将通信频带划分成频带较宽互不重叠的若干子载波,相邻子载波间并不设置保护频带,并将信息码元经过串并转换后调制到不同的子载波上进行传输。阐述了所提方法的原理,并设计了相应的试验对所提方法的有效性进行了验证。理论分析和试验结果表明,由于所提方法利用FMT技术降低了 PTR处理后残余干扰影响的码元范围,因此与现有的SC调制的MIMO-PTR水声通信方法相比,所提方法的信道估计、PTR处理以及干扰抑制的运算复杂更低,并且通信性能更优。
[Abstract]:In recent years, more and more marine activities have been engaged in shallow water. More and more attention and attention are paid to underwater acoustic communication technology. The rate and performance of underwater acoustic communication are higher. The Multiple-input multiple-output (MIMO) technology can make use of the weak space of underwater acoustic channel in shallow water environment. Correlation is used to gain a rich spatial degree of freedom, so it can improve the rate and communication performance of underwater acoustic communication. Time reversal (TR) has low computational complexity, and its good space-time focusing characteristics can reduce Intercode interference (Inter-symbol interference, ISI) and space caused by the multipath effect of shallow water channels. Co-channel interference (CCI) resulting from the inter correlation, so the communication system can achieve good communication performance with a lower complexity. According to the different implementation process of the space-time focus, the TR technology is divided into active time inverse (Active time reversal, ATR) and the active time reversal (Passive time reversal, PTR). In the process, the time interval between the detection signal and the information signal is shorter, and it can ensure the consistency of the estimated channel and the actual transmission channel. Therefore, PTR is more suitable for the actual shallow water environment. In the face of high speed and high performance underwater acoustic communication, it is of great theoretical and practical significance to study MIMO-PTR underwater acoustic communication technology. The current research status and development trend of MIMO-PTR underwater acoustic communication, combined with the characteristics of MIMO technology and PTR technology, focuses on the detailed study of the residual ISI and CCI suppression methods after PTR processing in MIMO-PTR underwater acoustic communication. The validity of the method is proved by theoretical deduction, simulation analysis and test verification. In the next few aspects, the study of.1 is carried out to study the interference suppression performance of PTR in underwater acoustic communication. The space-time focusing performance of.PTR can compress the multipath effect of the underwater acoustic channel, reduce the spatial correlation of the transmission channel corresponding to the information signals transmitted by different emitter elements, and then achieve the interference of reducing the ISI and CCI and improving the communication performance effect of.PTR. The suppression performance directly determines the residual ISI and CCI, and then determines the complexity of other technologies used for post-processing. The existing research on PTR underwater acoustic communication is divided into two aspects: single input and multiple output (Single-input multiple-output, SIMO) PTR underwater acoustic communication and MIMO-PTR underwater acoustic communication using spatial diversity and space division multiplexing simultaneously. Therefore, based on the research status of PTR underwater acoustic communication, the interference suppression performance of PTR is analyzed. First, through theoretical deduction, the technical index to measure the interference suppression performance of PTR, the general expression of the signal interference noise ratio, is obtained, and then the shallow sea channel model is established based on the ray acoustic theory and the geometric structure of the channel. This is based on the analysis of the influence of the number of receiving array elements, the number of emitter elements and the signal-to-noise ratio on the interference suppression performance of PTR. The results show that there will be residual interference after PTR processing, whether in SIMO-PTR underwater communication or at the same time using space diversity and space division multiplexing in MIMO-PTR underwater communication. High communication performance requires the use of adaptive equalization and adaptive interference cancellation for post-processing.2, and the study of MIMO-PTR underwater acoustic communications based on Time-reversal space-time block coding (TR-STBC) based on.PTR underwater communication.PTR underwater communication, the interference suppression performance of PTR is related to the spatial diversity gain. In less time, the existing SIMO-PTR underwater acoustic communication method is only by receiving diversity, the gain of spatial diversity is low, so the performance of PTR is poor and the complexity of adaptive equalization for PTR post-processing is high. In order to further improve the interference suppression performance of PTR by using transmit diversity, a MIMO-PTR underwater communication based on TR-STBC is proposed in this paper. Method. The proposed method is based on the principle of the 2 element TR-STBC scheme suitable for the frequency selective channel and the principle of the STBC scheme suitable for any emitter element 1/2 bit rate, and designs a TR-STBC scheme for the rate of 1/2 code for any emitter element, and combines the TR-STBC scheme with PTR in underwater acoustic communication. The principle of the proposed method is analyzed, and the effectiveness of the proposed method is simulated and tested. The results show that the proposed method uses the transmit diversity to improve the interference suppression performance of PTR. Therefore, compared with the SIMO-PTR underwater acoustic communication method, the proposed method has a lower complexity of adaptive equalization and PTR processing. The later performance is better.3, and the study of MIMO-PTR underwater acoustic communication based on continuous ISI and CCI, while using space diversity and space division multiplexing MIMO-PTR underwater acoustic communication, can effectively suppress ISI and CCI in underwater acoustic communication through the space time focusing of PTR, but the residual ISI and CCI still exist in the signal after PTR processing, which will affect the communication. In order to reduce the residual ISI and CCI after PTR processing with lower computational complexity, based on the design principle of continuous interference cancellation (Successive interference cancellation, SIC) technology and the characteristics of the combined channel response after PTR processing, a MIMO-PTR underwater acoustic communication method is proposed for continuous ISI and CCI cancellation. First, the proposed formula is analyzed. The principle of the method is then used to verify the effectiveness of the proposed method in the actual underwater environment by using the channel pool and the test data obtained from the Pine Lake test in Jilin province. The theoretical analysis and experimental results show that the proposed method can effectively suppress the residual interference after the PTR treatment, so that the MIMO-P has not been treated with any technology. Compared with the TR underwater acoustic communication, the communication performance of the proposed method is better. Compared with the existing SIC based MIMO-PTR underwater acoustic communication method, the proposed method has a lower computational complexity under the similar communication performance, and the MIMO-PTR underwater acoustic communication method based on the Filtered multitone, FMT modulation is studied. When the communication bandwidth is wide, the method is also beneficial. If single carrier modulation (Single-carrier, SC) technology is used for MIMO-PTR underwater communication with space diversity and space division multiplexing, the bit range of residual interference after PTR processing will be larger. This will result in poor performance after PTR processing and the interference suppression techniques used in post-processing are more complex. Based on this problem, FMT technology is used. In this paper, a FMT modulated MIMO-PTR underwater acoustic communication method is proposed. The proposed method uses FMT technology to divide the communication band into several subcarriers with wide bandwidth and no overlap. The adjacent subcarriers do not set the protection band, and the information symbols are modulated to different subcarriers after the conversion. The proposed method is described. The theoretical analysis and test results show that, as the proposed method uses FMT technology to reduce the symbol range of the residual interference after PTR processing, the proposed method is compared with the existing SC modulation MIMO-PTR underwater acoustic communication method, the proposed method of channel estimation, PTR processing. As well as interference suppression, the computation complexity is lower, and the communication performance is better.
【学位授予单位】：哈尔滨工程大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN929.3

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