【作者】 谷蓉婷；

【导师】 陈彦辉；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2008， 硕士

【摘要】 CPM调制是有记忆的恒包络调制方式,对功放的非线性特性不敏感;连续相位使带外辐射减小,具有较高的带宽效率;且CPM本身具有一定的编码增益,拥有较高的功率效率;采用高阶CPM调制可以提高传信率。码字很长的二进制LDPC码已被证明拥有逼近香农限的良好性能;而对于中等码长,可以通过设计定义在高阶GF(q)上的LDPC码来提高误码性能。本文研究了多进制LDPC码与高阶CPM调制相结合的串行级联系统。但是在具体实现时,高阶CPM调制的解调以及多进制LDPC码的构造和译码都面临复杂度上的挑战。针对这一问题,本文给出了相应的解决方案。在构造多进制LDPC码的校验矩阵时,使用一种新的方法来计算泰纳图的最小环长,有效的降低了计算复杂度,改进了二次置换多项式构造准循环LDPC码的算法。且多进制LDPC码的译码采用傅立叶快速算法。同时,为降低高阶CPM解调的复杂度,采用了最小均方误差下CPM的PAM分解模型;基于该模型简化了CPM的匹配滤波器,并给出似然概率的计算方法,及CPM的软输入软输出解调器,实现了CPM解调与LDPC之间的迭代译码。更多还原

【Abstract】 The serial concatenated system of non-binary LDPC codes over GF (q) and M-ary CPM modulation is studied in this paper. CPM is a memory modulation scheme with the advantages of constant signal envelope and excellent power and bandwidth efficiency.LDPC codes have been shown to approach Shannon limit performance for binary LDPC with long code length, on the other hand, for moderate code lengths, the error performance can be improved by increasing q, which Non-binary LDPC is designed over GF(q). Derived from such advantages, the serial concatenation, with joint iterative decoding between the CPM detector and LDPC decoder, is designed to achieve good performance over AWGN or fading channel.The construction, decoding of Nonbinary LDPC Codes and the detection of high-order CPM modulation face the challenge of complexity. In order to simplify, a fast algorithm, which is applied to quadratic permutation polynomials (QPP) construction, is proposed to compute the girth of Tanner graph of LDPC. Quasic-regular nonbinary LDPC construction, which can be implemented simply on hardware, is also investigated. The FFT BP algorithm is used to decoding the nonbinary LDPC. Huang and Li’s PAM approximate decomposition of CPM under MMSE is used to simplify the Match filter and detectior. A soft-in soft-out detection of CPM is designed in order to implement the iterative decoding, as well as an algorithm to approximate the likely probability.更多还原