基于混合簇稀疏/散射信道建模的水声异步双向中继传输方法研究

We have proposed a asynchronous two-way relaying (TWR) scheme in underwater acoustic (UWA) channel with hybrid clustered sparse/diffuse modeling. The proposed scheme has the ability of improving the spectral efficiency and transmission rate and security, as well as saving the transmission power over traditional UWA one-way relaying scheme. Based on the UWA hybrid clustered sparse/diffuse modeling, a association model incorporating both the UWA channel model and the TWR model will be established. By constructing the new structure of UWA TWR cascaded channel and designing optimal pilot symbols and modes, an estimation method for UWA TWR cascaded channel will be proposed. The identifiability problems on the nonambiguous estimate of the channels will be solved by a precoding based method, after which the UWA TWR indiviual channel estimates will be recovered. The data detection in asynchronous UWA TWR with nonuniform Doppler shifts will be accomplished by an iterative method, which will incorporate the design of preamble and postamble of a packet and the truncation of the received signals, as well as the resampling of the received waveform and high-resolution compensation of the Doppler. Water tank and lake experiments will be conducted to test and improve the proposed theory and method. Infulence rules and mechanisms of UWA physical layer characteristics on TWR will be uncovered. The anticipated achievements have both theoretical significance and application value in enriching and extending the theory of TWR communication, as well as developing UWA communication technologies and UWA networks.

本项目针对水声双向数据交互提出一种基于混合簇稀疏/散射信道建模的水声异步双向中继传输方法，能够提高传统水声中继方法的频谱效率、传输速率、安全性并降低能源消耗。基于水声混合簇稀疏/散射信道建模，建立水声信道与双向中继网络的关联模型；通过构建水声双向中继级联信道的新结构，结合对最优导频符号及导频模式的设计、对直连信道非模糊可识别性的判别，对水声双向中继级联信道和水声双向中继直连信道进行有效估计；通过信号重采样及高分辨率多普勒补偿消除子载波间的干扰，结合对传输信号的设计及接收信号块的截断，构建迭代方法对非均匀多普勒扩展水声信道中的异步双向中继数据进行准确检测；通过水池/湖上实验验证并完善所提出的理论方法，揭示水声信道物理层传输特性对水声双向中继传输的影响规律和作用机理。该项目预期成果将丰富和拓展双向中继通信理论的内涵和外延，对水声通信技术的发展和水声通信网络的建立有着重要的理论意义和应用价值。

本项目针对水声双向数据交互提出一种水声异步双向中继传输方法。通过对水声信道与双向中继网络的关联模型、水声双向中继信道估计方法、水声异步双向中继数据检测方法以及实验研究等内容的探索，系统而深入地研究了水声异步双向中继传输方法。1、在丹江口水库进行了水声信道物理层传输特性试验。测试得到的声速曲线与典型声速曲线的结果一致；信道的最大多径时延很大，多径非常密集，且无明显的能量主径；多普勒频移相对较小，但信道结构在某个特定时刻会发生明显改变；当接收端位置改变时信道结构会发生明显改变。利用测试得到的水声信道特性对水声双向中继通信进行了分析。2、研究了基于放大转发中继的双向中继网络中的联合时-频同步与信道估计方法。建立了双向中继网络中的联合时-频同步与信道估计模型，提出了混合贝叶斯算法来对双向中继网络中的联合时-频同步于信道估计问题进行求解。提出了重新参数化模型，将自干扰信道的后验分布从非标准分布转化为均值和方差未知的正态分布，从而便于贝叶斯采样，且无需求解噪声功率，从而简化了问题的求解。分别采用均匀分布和共轭分布作为先验分布，并据此验证了算法的鲁棒性。3、研究了基于放大转发协议的水声双向中继网络中的数据盲检测方法。建立了存在不确定时间延迟、载波频率偏移和相位噪声的水声双向中继网络中的数据盲检测系统模型。提出了近似贝叶斯算法来对水声异步双向中继网络中的传输数据进行盲检测。该方法基于贝叶斯准则和泰勒级数截断近似，并对参数的限制条件信息采用先验概率的形式进行表征来进一步提高检测性能。分别基于隐式自干扰抵消和显式自干扰抵消策略，提出了三种数据检测方法，即隐式自干扰抵消盲数据检测、显式自干扰抵消盲数据检测和基于训练序列的显式自干扰抵消数据检测方法。4、开展了相关实验研究。该项目研究成果将丰富和拓展中继通信理论的内涵和外延，能够提高传统水声中继方法的频谱效率、传输速率、安全性并降低能源消耗。