基于DVB-RCS2的CPM信号接收关键技术研究

发布时间：2018-02-15 01:06

本文关键词： 连续相位调制 DVB-RCS2 小波脊线符号速率估计 Laurent分解定时同步非对称非正交指数分解软输入软输出　出处：《解放军信息工程大学》2014年硕士论文　论文类型：学位论文

【摘要】：连续相位调制(Continuous Phase Modulation,CPM)由于具有很高的频谱利用率和功率利用率,在卫星通信系统中的应用十分广泛。2011年公布的DVB-RCS2协议将CPM引入其回传链路传输模式中,调制参数更加灵活多样,对CPM信号接收技术提出了更高的要求。本文基于DVB-RCS2协议,研究实现了协议规定下CPM信号的符号速率估计、定时同步和解调译码算法。论文工作为作者所在实验室承担的某重点项目的一部分。本文的主要工作和创新点概括如下:1、分析了DVB-RCS2协议中回传链路的CPM传输模式,通过解析信令和突发波形生成过程,明确了协议规定下CPM信号的调制参数特点和接收关键步骤。2、提出了一种基于小波脊线的CPM信号符号速率估计算法。通过研究CPM信号的小波脊线特征,对基带CPM信号的小波脊线进行滤波处理,再做FFT运算得到离散谱线,根据离散谱线与符号速率的关系,实现CPM信号符号速率的估计。针对DVB-RCS2协议规定信号进行仿真实验,结果表明,该算法适用于回传链路的短突发和低信噪比环境,与现有算法相比,受载波频偏、相偏和调制指数影响更小。3、提出了一种低复杂度的CPM信号联合定时和序列检测算法。在基于最大似然的判决反馈结构基础上,首先通过Laurent分解简化前端匹配滤波器组,降低Viterbi算法所需分支度量的计算复杂度,进一步利用减少状态序列检测算法简化后端状态转移网格,改进判决反馈结构,实现了CPM信号的定时同步和序列检测的联合优化。针对DVB-RCS2协议信号进行仿真实验,表明该算法相较现有算法更适用于多进制部分响应CPM信号,收敛速度更快,精度更高。4、提出了一种低复杂度的串行级联CPM信号解调译码算法。在传统的软输入软输出迭代译码算法基础上,利用非对称非正交指数分解近似表达参考信号,修正串行级联结构中CPM内码分支度量的计算,在保证提供充分统计信息的基础上降低运算复杂度。针对DVB-RCS2协议信号进行仿真实验,表明该算法与现有算法相比,在解调性能损失更小的基础上运算复杂度更低。5、实现了CPM信号参数估计和解调译码的系统功能模块。依托硬件平台,完成了所研算法的软件实现,并利用实验信号进行性能测试,结果表明本文算法能够达到预期效果,为DVB-RCS2信号接收系统的实现打下基础。
[Abstract]:Continuous Phase Modulation (CPM) is widely used in satellite communication systems because of its high spectral efficiency and power efficiency. The DVB-RCS2 protocol published in 2011 introduces CPM into its return link transmission mode, and the modulation parameters are more flexible. In this paper, based on the DVB-RCS2 protocol, the symbol rate estimation of the CPM signal under the protocol is studied and realized. Timing synchronization and demodulation decoding algorithms. This paper is a part of a key project in the laboratory. The main work and innovation of this paper are summarized as follows: 1. The CPM transmission mode of the return link in DVB-RCS2 protocol is analyzed. By analyzing signaling and burst waveform generation, The characteristics of modulation parameters and the key steps of receiving CPM signal under protocol are defined. A symbol rate estimation algorithm for CPM signal based on wavelet ridge is proposed. The wavelet ridge feature of CPM signal is studied. The wavelet ridge of baseband CPM signal is filtered, then the discrete spectral line is obtained by FFT operation. According to the relation between discrete spectral line and symbol rate, the symbol rate of CPM signal is estimated. The simulation experiment is carried out for the signal specified in DVB-RCS2 protocol. The results show that the proposed algorithm is suitable for short burst and low signal-to-noise ratio (SNR) environments of the return link. The phase offset and modulation exponent are less affected. 3. A low complexity joint timing and sequence detection algorithm for CPM signals is proposed. Based on the decision feedback structure based on maximum likelihood, the front-end matched filter banks are simplified by Laurent decomposition. The computational complexity of the branch metric required by Viterbi algorithm is reduced, and the reduced state sequence detection algorithm is further used to simplify the back-end state transition grid, and the decision feedback structure is improved. The timing synchronization of CPM signal and the joint optimization of sequence detection are realized. The simulation results of DVB-RCS2 protocol signal show that the proposed algorithm is more suitable than the existing algorithms for multi-ary partial response to CPM signal, and the convergence speed is faster. A low complexity serial concatenated CPM signal demodulation and decoding algorithm is proposed. Based on the traditional soft-input soft-output iterative decoding algorithm, the asymmetric nonorthogonal exponential decomposition is used to approximate express the reference signal. The computation of CPM internal code branch metric in serial concatenated structure is modified, and the computational complexity is reduced on the basis of guaranteeing sufficient statistical information. The simulation experiments on DVB-RCS2 protocol signal show that the proposed algorithm is compared with the existing algorithms. On the basis of less performance loss of demodulation, the computational complexity is lower. 5. The system function module of parameter estimation and demodulation and decoding of CPM signal is realized. Based on hardware platform, the software implementation of the algorithm is completed. The experimental results show that the proposed algorithm can achieve the desired results and lay the foundation for the realization of the DVB-RCS2 signal receiving system.
【学位授予单位】：解放军信息工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.25

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