隐蔽通信中的Turbo码并行译码

摘要

针对隐蔽通信的低信噪比应用背景,引入高效信道编码Turbo码提高系统可靠性,并提出一种基于尾比特插入的并行译码算法以减小译码时延并提高码字的保密性.该算法在编码过程中周期插入归零比特使编码器回归到确知状态,译码器根据尾比特的位置划分子块并确定各并行子译码块的初始化值.所插入尾比特可看作“伪信息”,具有随机性,增强了通信的保密性.仿真结果表明,相对于传统并行译码,所提译码方案在提高Turbo码译码速率减小译码延时的同时,不会因为边界条件模糊而产生性能损失,适用于极低信噪比的隐蔽通信环境.%In covert communication with low signal-to-noise ratio, Turbo codes are used as channel coding to improve system reliability. A parallel decoding algorithm is proposed by inserting tail bits to reduce decoding delay and improve confidentiality. The periodical tail bits make the encoder return to a known status. In the decoder, the initial values of sub-blocks can be obtained from the zero-tail bits. The random tail bits can be viewed as pseudo information. Thus, confidentiality of the communication is enhanced. Simulation results show that, compared with conventional parallel decoding methods, the proposed scheme can improve Turbo decoding rate and reduce time delay without performance loss due to unknown boundary. The algorithm is suitable for high-speed communications in a low SNR environment.