發(fā)布時間：2018-02-15 01:06

  本文關鍵詞： 連續(xù)相位調制 DVB-RCS2 小波脊線 符號速率估計 Laurent分解 定時同步 非對稱非正交指數分解 軟輸入軟輸出　出處：《解放軍信息工程大學》2014年碩士論文　論文類型：學位論文

【摘要】：連續(xù)相位調制(Continuous Phase Modulation,CPM)由于具有很高的頻譜利用率和功率利用率,在衛(wèi)星通信系統(tǒng)中的應用十分廣泛。2011年公布的DVB-RCS2協(xié)議將CPM引入其回傳鏈路傳輸模式中,調制參數更加靈活多樣,對CPM信號接收技術提出了更高的要求。本文基于DVB-RCS2協(xié)議,研究實現(xiàn)了協(xié)議規(guī)定下CPM信號的符號速率估計、定時同步和解調譯碼算法。論文工作為作者所在實驗室承擔的某重點項目的一部分。本文的主要工作和創(chuàng)新點概括如下:1、分析了DVB-RCS2協(xié)議中回傳鏈路的CPM傳輸模式,通過解析信令和突發(fā)波形生成過程,明確了協(xié)議規(guī)定下CPM信號的調制參數特點和接收關鍵步驟。2、提出了一種基于小波脊線的CPM信號符號速率估計算法。通過研究CPM信號的小波脊線特征,對基帶CPM信號的小波脊線進行濾波處理,再做FFT運算得到離散譜線,根據離散譜線與符號速率的關系,實現(xiàn)CPM信號符號速率的估計。針對DVB-RCS2協(xié)議規(guī)定信號進行仿真實驗,結果表明,該算法適用于回傳鏈路的短突發(fā)和低信噪比環(huán)境,與現(xiàn)有算法相比,受載波頻偏、相偏和調制指數影響更小。3、提出了一種低復雜度的CPM信號聯(lián)合定時和序列檢測算法。在基于最大似然的判決反饋結構基礎上,首先通過Laurent分解簡化前端匹配濾波器組,降低Viterbi算法所需分支度量的計算復雜度,進一步利用減少狀態(tài)序列檢測算法簡化后端狀態(tài)轉移網格,改進判決反饋結構,實現(xiàn)了CPM信號的定時同步和序列檢測的聯(lián)合優(yōu)化。針對DVB-RCS2協(xié)議信號進行仿真實驗,表明該算法相較現(xiàn)有算法更適用于多進制部分響應CPM信號,收斂速度更快,精度更高。4、提出了一種低復雜度的串行級聯(lián)CPM信號解調譯碼算法。在傳統(tǒng)的軟輸入軟輸出迭代譯碼算法基礎上,利用非對稱非正交指數分解近似表達參考信號,修正串行級聯(lián)結構中CPM內碼分支度量的計算,在保證提供充分統(tǒng)計信息的基礎上降低運算復雜度。針對DVB-RCS2協(xié)議信號進行仿真實驗,表明該算法與現(xiàn)有算法相比,在解調性能損失更小的基礎上運算復雜度更低。5、實現(xiàn)了CPM信號參數估計和解調譯碼的系統(tǒng)功能模塊。依托硬件平臺,完成了所研算法的軟件實現(xiàn),并利用實驗信號進行性能測試,結果表明本文算法能夠達到預期效果,為DVB-RCS2信號接收系統(tǒng)的實現(xiàn)打下基礎。
[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.
【學位授予單位】：解放軍信息工程大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN911.25

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