For satellite communication with bi-directional channels, we investigate the application of Low-Density Parity-Check (LDPC) coding by incorporating channel state information (CSI) to enhance its security performance. Specifically, the scheme includes two main steps: CSI measurement and the design of LDPC security coding. Based on its reciprocity and uniqueness, CSI is first obtained by estimating bidirectional channels followed with quantization and reconciliation, which results in the binary sequence of the CSI. In this work, based on the characteristics of satellite communication, the extended irregular repeat-accumulate (eIRA) of LDPC codes were adapted in order to reduce the storage capacity and computational complexity. Finally, LPDC secure coding scheme utilizes a scrambling matrix that is converted from the CSI’s binary sequence to complete the LDPC coding process. Based on NI USRP 2920, a simulation platform was developed to study the performance of the proposed scheme. The evaluation results show that our proposed scheme can improve the reliability of received information for the legitimate receivers, while leading to increased bit error rates for the eavesdroppers, and thus enhance the communication security.

对于双向信道的卫星通信，我们通过结合信道状态信息（CSI）来增强其安全性能，研究低密度奇偶校验（LDPC）编码的应用。具体而言，该方案包括两个主要步骤：CSI测量和LDPC安全编码的设计。基于其互惠性和唯一性，首先通过估计双向信道，然后进行量化和协调，获得CSI的二进制序列，从而获得CSI。在这项工作中，根据卫星通信的特性，对LDPC码的扩展不规则重复累加（eIRA）进行了调整，以减少存储容量和计算复杂性。最后，LPDC安全编码方案利用从CSI的二进制序列转换而来的加扰矩阵来完成LDPC编码过程。基于NI USRP 2920，开发了一个仿真平台来研究所提出方案的性能。评估结果表明，本文提出的方案可以提高合法接收者接收信息的可靠性，同时提高窃听者的误码率，从而提高通信安全性。