Abstract: EBF algorithm is one of the best known methods for constructing LDPC codes at short and intermediate block lengths, however, the codewords directly designed by such algorithm have high encoding complexity, which hinders the development of LDPC codes in the practical process. The paper presents an improved EBF algorithm based on iterative encoding method with the linear coding complexity, the aim is to make the coding complexity lower through the improvement of coding scheme and the structure of parity-check matrix. The simulation results indicate that, in the condition of BPSK、QPSK and 16QAM modulations, though there are the same error correct performance between the codewords constructed by improved EBF algorithm proposed in this paper and codewords constructed by EBF algorithm, the powerful advantage lies in the lower hardware complexity.

Key words: communication and information system, Extended Bit-Filling（EBF） algorithm, iterative encoding, lower triangular form, Low Density Parity Check（LDPC）, bit error rate

摘要： 扩展比特填充（EBF）构造算法是迄今为止构造性能优异的中短码长LDPC码的一种有效的构造方法，然而直接采用该算法构造的LDPC码的编码复杂度正比于码长的平方，使其成为实用化过程中的一个瓶颈。基于具有线性编码复杂度的迭代编码算法提出了一种改进的EBF构造算法，通过对编码方案的改进和校验矩阵的构造两个方面降低其复杂度。仿真结果表明，在BPSK、QPSK及16QAM调制方式下，虽然改进的EBF构造算法构造的LDPC码码字与EBF构造算法构造的码字的纠错性能基本一致，但是其最大的优势在于具有更低的硬件实现复杂度。

关键词: 通信与信息系统, 扩展比特填充算法, 迭代编码, 下三角结构, 低密度奇偶校验码, 误码率