基于协作干扰的不可信中继网络安全传输优化理论与方法研究

With the urgent requirement of improving the security in wireless communications, physical-layer security has attracted a lot of attention both in theoretical study and practical applications. In this project, to increase the secrecy rate with physical layer security, we study the optimized secure transmission in a cooperative jamming-based untrusted relay network. For multi-antenna scenario with more degrees of freedom, we propose a novel precoder design based on signal alignment technology and a joint optimization of precoder and power allocation. For single-user-pair and multi-relay scenario, we study the relay selection strategies and propose the simplified modeling and solution in transformation domain. Then for multi-user-pair and multi-relay scenario, we devise an optimized matching strategy based on bipartite graph, and study its optimal matching solution based on modified Hungarian method. For multi-hop and multi-relay scenario, we design a reliable communication protocol, develop a demodulation method based on Viterbi algorithm, and propose heuristic strategies for route selection. Further extending the previous work to practical applications, there exists residual interference after self-interference cancellation due to imperfect channel state information (CSI). Therefore, we further evaluate the performance loss and study the robust precoder design with the statistical characteristics of imperfect CSI. The key issues needed to be addressed include equivalent modeling for joint optimization of multiple parameters and its efficient solution, robust design considering imperfect CSI, and algorithm design trading off performance, complexity and robustness for complicated optimization problems. We aim to achieve some innovative fruits on physical layer security and establish a set of theory and method for optimized secure transmission in an untrusted relay network. All the products are expected to provide fundamental basis for secure transmission in future wireless communication systems.

改善无线通信安全需求十分迫切，物理层安全得到广泛重视。围绕物理层安全速率提升问题，开展基于协作干扰的不可信中继网络安全传输优化理论和方法研究。针对多天线配置，研究基于信号对齐的预编码和功率分配联合优化；针对单用户对-多中继场景，研究中继选择策略，探索基于变换域的中继选择优化建模和求解方法；针对多用户对-多中继场景，研究基于二部图的匹配优化，探索基于匈牙利算法的最优匹配求解；针对多跳-多中继场景，设计可靠通信协议，探索基于Viterbi算法的解调方法，研究启发式路由选择策略；考虑实际应用，评估非理想CSI造成的性能损失，开展CSI误差统计特性已知的稳健设计。拟解决的关键问题包括多参数联合优化等价建模及其高效求解方法、稳健设计、以及求解复杂优化问题时性能、复杂度和稳健性折中的算法设计。力求取得创新性成果，建立一套不可信中继网络安全传输优化设计的理论与方法，为解决未来无线安全通信积累理论基础。

针对本项目所有研究工作，团队制定了详细的研究计划，完成了预定的研究任务，并取得了预期的目标，具体如下：.(1)多天线不可信中继网络的预编码与功率分配优化设计.针对单向、多天线不可信中继传输网络，以最大化系统安全速率为目标，建立了波束形成和功率分配联合优化模型，基于GSVD设计了有用信号发送预编码，给出了迭代方案实现多参数联合优化。进一步研究双向、多天线不可信中继网络的联合优化问题，提出了二层迭代优化算法。.(2)单用户对、多中继不可信网络的最优中继选择策略的研究.针对单用户对、多不可信中继、双向传输网络，研究了基于安全速率最大化和基于最小单向安全速率最大化的两种中继选择策略；为进一步降低复杂度，提出了一种基于广义奇异值分解的中继选择策略。对研究的三种中继选择策略的复杂度进行了对比分析。.(3)多用户对多中继不可信网络的最优匹配算法的研究.将多用户对与多中继的最优匹配问题抽象为二部图问题，提出了两种权重设计方案。基于权重设计和KM算法，研究了三种用户对-中继匹配算法。评估了不同权重设计方案的复杂度。在此基础上，考虑多辅助干扰节点网络，继续研究了多用户对与多不可信中继的匹配问题。.(4)多跳、多中继不可信网络的路由选择算法.考虑安全性，设计了通信协议，对信号传输模型进行了分析，基于Viterbi算法提出了两种路由选择算法：基于信道增益最大化的路由选择算法和兼顾信道增益和中继簇内干扰的路由选择算法。进一步，评估了两种路由选择算法的复杂度差异，并分析了滑动窗长度对实现复杂度的影响。.(5)非理想CSI不可信中继网络稳健优化设计.对于信道估计误差有界和服从高斯分布两种条件，推导了遍历安全速率，并基于这一指标最优化功率分配方案，实现稳健设计。针对PSK调制下具有多个窃听者的单用户多输入单输出(MISO)窃听信道，设计了一种针对不完美信道状态信息的鲁棒符号级预编码安全方法。.在本项目的支持下，已发表学术论文33篇；申请专利11项；出版专著1部；培养学生14名。