本文關(guān)鍵詞： Turbo編譯碼 MAX-Log-MAP 線性擬合 比例因子 FPGA　出處：《武漢理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：Turbo碼以其具有良好的逼近香農(nóng)極限的譯碼性能,在無線通信領(lǐng)域中起到了舉足輕重的作用,并成了當(dāng)今信息時代研究糾錯編碼的重要課題之一。在人們生活質(zhì)量不斷提高的信息時代,通信系統(tǒng)中對工具的便捷性和技術(shù)的有效性要求也越來越嚴(yán)格,以促使人們對通信系統(tǒng)的關(guān)注越來越緊密�，F(xiàn)在隨著4G的推出,人們能夠享受4G帶來的更快的速度和更高的性能,而這一進步正是由于通信工程師們對通信協(xié)議、算法等不斷的研究和改進的成果,其中,Turbo碼作為通信系統(tǒng)中常用的編解碼算法之一,在算法的研究上也不斷的得到了改進和創(chuàng)新。通過研究Turbo碼編碼器和譯碼器結(jié)構(gòu),并詳細介紹了編解碼各個模塊的實現(xiàn)原理。其中,對于編碼模塊,詳細分析了分量編碼器和交織器兩個關(guān)鍵問題;對于譯碼模塊,對比了Turbo碼常用的兩種譯碼算法:SOVA和MAP,并詳細針對MAP算法進行了數(shù)據(jù)推導(dǎo)和分析,同時針對碼率、交織長度和迭代次數(shù)的不同分別研究了Turbo碼的譯碼性能。本文對MAX-Log-MAP算法主要從以下兩個方面做了改進,第一方面,對MAP算法兩路信號局限性進行了擴展分析,當(dāng)有多路信號時,對算法進行了優(yōu)化和近似分析;另一方面,針對MAX-Log-MAP算法中忽略的修正函數(shù)入手,考慮了修正函數(shù)的影響,并對修正函數(shù)進行了線性擬合,同時加入了外信息的比例因子,并且從性能和復(fù)雜度角度分析算法的有效性,通過MATLAB工具對算法的性能從不同的角度進行了驗證。得到了以下結(jié)論:在損失了一定復(fù)雜度的前提下,有效地提高了算法的譯碼性能。在FPGA的實現(xiàn)中,借助XILINX設(shè)計軟件ISE12.2,完成了對編碼碼率為1/3,量化寬度為7bits的Turbo碼編解碼結(jié)構(gòu)的方案設(shè)計,并通過ISE軟件仿真平臺使用硬件編程語言Verilog,完成了編解碼的FPGA實現(xiàn),在編碼實現(xiàn)結(jié)構(gòu)中,完成了分量碼、交織、并串和串并的轉(zhuǎn)換,借助了三分頻的思想。在信道端,由于信號在實際的傳輸過程中會受到噪聲的干擾,為了模擬真實的信號通信過程,所以本文中還借助MATLAB模擬了離散的AWGN信道。在譯碼實現(xiàn)結(jié)構(gòu)中,分別采用MAX-Log-MAP算法和新提出的改進算法的譯碼器完成譯碼功能,并對仿真結(jié)果進行驗證。根據(jù)對Turbo碼性能的分析,以及Turbo碼在各個領(lǐng)域的廣泛應(yīng)用,其算法和結(jié)構(gòu)會不斷的得到研究和改進,進而成為通信行業(yè)中最有效的編碼技術(shù)。
[Abstract]:Turbo codes play an important role in wireless communication field because of their good decoding performance of approaching Shannon limit. And it has become one of the important topics of error correction coding in the information age. In the information age where people's quality of life is improving, the convenience of tools and the effectiveness of technology are becoming more and more strict in communication system. Now with 4G, people can enjoy the faster speed and higher performance that 4G brings, and this progress is due to the communication protocols that communications engineers have. As one of the commonly used coding and decoding algorithms in communication systems, turbo codes have been continuously improved and innovated in the research of the algorithms. The realization principle of each module is introduced in detail. The key problems of component encoder and interleaver are analyzed in detail for the coding module, and for the decoding module, In this paper, two common decoding algorithms of Turbo codes, namely: SOVA and MAPP, are compared, and the data of MAP algorithm is deduced and analyzed in detail, and the code rate is also analyzed. In this paper, the decoding performance of Turbo codes is studied with different interleaving lengths and iterations. The MAX-Log-MAP algorithm is improved from the following two aspects. Firstly, the limitations of the two channels of MAP algorithm are extended and analyzed, when there are multichannel signals, The algorithm is optimized and approximate analyzed. On the other hand, the influence of the correction function is considered, and the correction function is fitted linearly, and the proportion factor of the external information is added to the modified function, which is ignored in the MAX-Log-MAP algorithm. The effectiveness of the algorithm is analyzed from the point of view of performance and complexity. The performance of the algorithm is verified from different angles through MATLAB tools. The following conclusions are obtained: under the premise of losing a certain complexity, In the implementation of FPGA, with the help of XILINX design software ISE12.2, the scheme of coding and decoding Turbo codes with 1 / 3 coding rate and 7 bits quantization width is completed. Through the ISE software simulation platform, using the hardware programming language Verilog, the FPGA implementation of coding and decoding is completed. In the coding implementation structure, the conversion of component code, interleaving, parallel string and series-parallel is completed, and the idea of three-frequency division is used. In order to simulate the real signal communication process, the discrete AWGN channel is simulated by MATLAB in order to simulate the real signal communication process because the signal will be disturbed by noise in the actual transmission process. The decoder of the MAX-Log-MAP algorithm and the new improved algorithm are used to complete the decoding function, and the simulation results are verified. According to the analysis of the performance of the Turbo code and the wide application of the Turbo code in various fields, Its algorithm and structure will be continuously studied and improved, and then become the most effective coding technology in the communication industry.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN791;TN911.22

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