面向隐蔽双站反向散射网络的性能优化

Performance Optimization of Covert Bistatic Backscatter Communication

针对双站反向散射通信(Backscatter Communication,BackCom)网络易遭受恶意窃听的问题,提出了隐蔽双站BackCom网络。推导了窃听者检测错误概率和BackCom传输中断概率来刻画其信息传输的隐蔽性与可靠性,并提出一种方法在满足隐蔽性约束下来进一步提高系统的传输性能。利用统计信道状态信息,在高信噪比条件下依次推导窃听者检测错误概率BackCom中断概率的闭合表达式。通过联合优化窃听者的检测阈值和BackCom发射机的反射系数,构建一个BackCom传输中断概率最小化的非凸多维资源分配问题。为了解决该非凸问题,采用块坐标下降法(Block Coordinate Descent,BCD)将其分解为两个子问题。在此基础上,深入分析子问题的结构特性并利用目标函数关于反射系数的单调递减特性设计一种基于BCD的迭代算法,以此求解转换问题。仿真结果验证了分析结果的正确性并且所提方案能够提升基准方案的性能,当传输速率为0.1 Mb/s时,系统的中断概率能够降低至10^(-2);对于较大传输速率,系统的中断概率仍保持在10^(-1)以下。

In order to solve the problem that bistatic backscatter communication(BackCom)networks are vulnerable to wiretapped threats from eavesdroppers,a covert bistatic BackCom network is proposed.To characterize the covertness and reliability of the information transmission,the probability of eavesdropper’s detection error probability and the outage probability of the BackCom are derived,and a method is proposed to further improve the transmission performance of the system,subject to the covertness constraints.Firstly,the closed-form expressions of eavesdropper’s detection error probability and BackCom’s outage probability are derived under the condition of high signal-to-noise ratio by exploiting the statistical channel state information.Secondly,a non-convex multi-dimensional resource allocation problem is formulated to minimize the BackCom transmission outage probability by jointly optimizing the detection threshold of the eavesdropper and the reflection coefficient of the BackCom transmitter.To solve the non-convex problem,the block coordinated descent(BCD)method is used to decompose it into two sub-problems.On this basis,after carefully inspecting the structure of the simplified sub-problems and using the characteristic that the objective function is a monotone decreasing function of the reflection coefficient,an iterative algorithm based on BCD is proposed to solve the conversion problem.The simulation results verify the correctness of the analysis results,and show that the proposed resource allocation scheme can improve the performance of the benchmark scheme.Specifically,the system outage probability degrades to less than 10^(-2) when the transmission rate is 0.1 Mb/s.For the larger transmission rate,the system outage probability remains below 10^(-1).