时间反转多用户系统中保密和速率优化的预处理滤波器设计

Pre-filter Design for Sum Secrecy Rate Optimization in Time-reversal Multiuser Systems

利用无线信道的特征通过物理层技术实现信息的安全传输是保密通信的一种方式。时间反转传输特有的时空聚焦特性使其具有天然的抗干扰和抗窃听能力,在单发射天线条件下也能获得较好的保密传输性能。该文研究两用户时间反转下行多址安全传输系统中,发送滤波器脉冲响应的优化问题。根据互惠原则将两个发送滤波器的联合优化问题转换为各滤波器的独立优化问题,进一步将其转换为寻找最大特征值及其对应的特征向量的问题,并通过迭代算法进行求解。仿真结果表明,针对保密和速率优化预处理滤波器后,系统的可达保密速率明显优于采用常规时间反转预处理滤波器时的系统和直接传输系统。

Utilizing the characteristics of the wireless channel to achieve secure transmission of information through physical layer technology is a way to realize security communications. The time-reversed transmission has natural anti-jamming and anti-eavesdropping capability due to its unique spatial and temporal focusing property, so a good secrecy performance can be obtained even when the transmitter is equipped with single transmitting antenna. This paper studies the optimization of the transmit filter impulse response in a two-user time-reversed downlink multiple access secure transmission system. The joint optimization problem of two transmitting filters is transformed into the independent optimization problem of each filter based on reciprocity principles. This problem is further converted into the problem of finding the largest eigenvalue and its corresponding eigenvector which is solved by iterative algorithm. The simulation results show that by optimizing the pre-filter for sum secrecy rate, the system’s sum secrecy rate is promoted and is obviously higher than that of the conventional time-reversed pre-processing filter system and direct transmission system.