新型LT码编译码方法及其在认知无线电中的应用

Luby变换(LT)码作为一种抗干扰编码技术，应用于认知无线电系统，可提高次用户数据传输的可靠性。编译码是影响LT码抗干扰性能的关键因素。为提高数据传输的可靠性和速度，该文提出一种适用于认知无线电系统的LT码联合泊松鲁棒孤子分布-叠层(CPRSD-H)编译码算法。编码过程中，编码器首先采用CPRSD进行编码产生编码分组和编码矩阵，随后通过编码矩阵中度数为1和度数为2对应的列向量携带双层信息：度数为1和度数为2的编码分组和与其相连接的输入分组的连接关系；部分原始数据信息。译码过程中，译码器首先通过第1层存储信息采用置信传播(BP)算法译码完成，随后一些未被成功译出的信息再通过第2层存储信息进行填补。仿真结果表明，将CPRSD-H编译码算法应用于认知无线电系统中，能够显著降低LT码的误比特率(BER)，提高次用户有效吞吐量以及加快LT码编译码速度。

A Novel Encoding and Decoding Method of LT Codes and Application to Cognitive Radio

As an efficient anti-interference technique, Luby Transform (LT) codes are applied to cognitive radio systems for reliable data transmission of secondary users. Encoding and decoding are critical issue for the anti-interference performance of LT codes. To improve the reliability and speed of data transmission, a novel encoding and decoding method Combined Poisson Robust Soliton Distribution-Hierarchical (CPRSD-H) for LT codes is proposed to apply to cognitive radio systems. In the process of encoding, the encoder first produces encoded symbols and generator matrix based on CPRSD, and then uses column vectors corresponding to degree–1 and degree–2 in the generator matrix to carry dual information: the relationship between the degree–1 and degree–2 encoded symbols and their connected input symbols; and part of the original data. Contrarily, in the decoding process, the decoder first uses the Belief Propagation (BP) algorithm to decode by the first information, and then correct some unrecovered bits by the second information. Simulation results show that the proposed method CPRSD-H and application to cognitive radio systems can significantly reduce the Bit Error Rate (BER) of LT codes, the goodput performance of secondary users and the encoding and decoding speed of LT codes.