本文選題：噴泉碼 + LT碼��； 參考：《杭州電子科技大學(xué)》2017年碩士論文

【摘要】：噴泉碼作為一種較新穎的信道編碼技術(shù),憑借其無率和一致特性,以及無需反饋、編譯碼復(fù)雜度低、中斷可續(xù)傳的優(yōu)點(diǎn),近些年成為通信領(lǐng)域研究的熱點(diǎn)之一。低密度奇偶校驗(yàn)(LDPC)碼是一類基于稀疏校驗(yàn)矩陣結(jié)構(gòu)的線性分組碼,其檢糾錯(cuò)能力強(qiáng),性能可逼近Shannon限,譯碼復(fù)雜度較低,硬件實(shí)現(xiàn)簡(jiǎn)單,在第四代移動(dòng)通信(4G)中有應(yīng)用,且目前已被確定為第五代移動(dòng)通信(5G)的長(zhǎng)碼編碼方案。為了對(duì)抗信息傳輸過程中信道的干擾,確保通信的可靠性,尤其對(duì)于某些特殊環(huán)境,如深空通信、雷電等傳輸時(shí)延大、鏈路質(zhì)量不佳的狀況,本文提出一種噴泉碼與LDPC碼級(jí)聯(lián)的編碼方案,并探討分析其性能與優(yōu)勢(shì)。本文首先介紹了數(shù)字噴泉碼和LDPC碼的理論知識(shí),并對(duì)兩類實(shí)用性噴泉碼—LT碼以及Raptor碼展開了詳細(xì)的研究,仿真分析了度分布對(duì)噴泉碼的譯碼性能的影響以及幾種常用的譯碼算法的性能及優(yōu)缺點(diǎn)。此外對(duì)LDPC碼的編譯碼算法的性能也進(jìn)行了仿真比較。在基于LDPC碼和噴泉碼的研究的基礎(chǔ)上,提出了兩者的級(jí)聯(lián)方案,為了綜合評(píng)價(jià)該種級(jí)聯(lián)方案,除AWGN信道外又建立了兩種特殊的信道模型,一是在某段時(shí)間內(nèi)發(fā)生了深衰落,二是在一段時(shí)間內(nèi)隨機(jī)出現(xiàn)多次短時(shí)信號(hào)中斷,利用內(nèi)碼的檢錯(cuò)刪除機(jī)制將非刪除信道模型等效為刪除信道,使其適合噴泉碼應(yīng)用。對(duì)噴泉-LDPC級(jí)聯(lián)碼在不同的信道模型下進(jìn)行了性能仿真,并嘗試通過改變內(nèi)碼的碼長(zhǎng)、碼率并加入交織來提高級(jí)聯(lián)碼的性能,此外還比較分析了噴泉-LDPC碼級(jí)聯(lián)方案和其它編碼方案的表現(xiàn)。研究結(jié)果表明,Raptor碼作為一種改進(jìn)的LT碼,在編譯碼復(fù)雜度和成功譯碼率方面均占據(jù)優(yōu)勢(shì),作為級(jí)聯(lián)碼的外碼更為合適;基于系統(tǒng)Raptor碼和LDPC碼的級(jí)聯(lián)編碼方案在AWGN信道以及構(gòu)造的信道上均有不錯(cuò)的性能,相比單純的LDPC碼而言,編碼增益有極大提高,其為信息的可靠傳輸提供了一種解決思路。最后闡述了Raptor-LDPC碼在DSP上實(shí)現(xiàn)的具體過程,涉及到定點(diǎn)量化、矩陣存儲(chǔ)、矩陣運(yùn)算等,并探討了不同量化方案和量化級(jí)數(shù)對(duì)Raptor-LDPC碼誤碼性能的影響,并發(fā)現(xiàn)選擇合適的量化方案可以將量化所造成的損失降到很低,減小對(duì)級(jí)聯(lián)碼性能的影響。通過理論研究和實(shí)際仿真可以發(fā)現(xiàn),LDPC碼和噴泉碼級(jí)聯(lián)不僅具有優(yōu)異的碼字性能,而且能保持較低的編譯碼復(fù)雜度,更為重要的是其拋棄了傳統(tǒng)的自動(dòng)反饋重傳(ARQ)機(jī)制,可極大地縮短文件的傳輸延時(shí),同時(shí)又確保成功譯碼率。它可用于深空通信、深海遠(yuǎn)程水聲通信等環(huán)境,有效應(yīng)對(duì)信道時(shí)變、傳輸時(shí)延長(zhǎng)、誤碼率高及通信鏈路易中斷的狀況。
[Abstract]:Fountain code, as a novel channel coding technology, has become one of the hotspots in the field of communication in recent years because of its advantages of low coding and decoding complexity and low complexity of coding and decoding without feedback. Low density parity check (LDPC) codes are a class of linear block codes based on sparse parity check matrix structure. They have strong error-correcting ability, approximate Shannon limit, low decoding complexity, simple hardware implementation, and are used in the fourth generation mobile communication system (4G). And has been identified as the fifth generation mobile communication 5 G long code coding scheme. In order to counteract the interference of the channel in the process of information transmission and ensure the reliability of the communication, especially in some special environment, such as deep space communication, lightning and other transmission delay, the link quality is not good. This paper presents a concatenation scheme of fountain code and LDPC code, and discusses its performance and advantages. In this paper, the theoretical knowledge of digital fountain codes and LDPC codes is introduced, and two kinds of practical fountain codes-LT codes and Raptor codes are studied in detail. The effect of degree distribution on the decoding performance of fountain code is analyzed by simulation, and the performance, advantages and disadvantages of several common decoding algorithms are also analyzed. In addition, the performance of LDPC encoding and decoding algorithm is also simulated and compared. Based on the research of LDPC code and fountain code, the concatenation scheme of LDPC code and fountain code is proposed. In order to evaluate the concatenation scheme, two special channel models are established in addition to the AWGN channel. Secondly, several short time signal interruptions occur at random for a period of time. The non-deleted channel model is equivalent to the deleted channel by the error detection and deletion mechanism of the inner code, which makes it suitable for the application of fountain code. The performance of fountain LDPC concatenated code is simulated under different channel models, and the performance of concatenated code is improved by changing the code length, code rate and interleaving. In addition, the concatenation scheme of fountain-LDPC code and other coding schemes are compared and analyzed. The results show that Raptor code, as an improved LT code, is more suitable as a concatenated code in terms of complexity and rate of successful decoding. The concatenated coding scheme based on system Raptor code and LDPC code has good performance in AWGN channel and constructed channel. Compared with the simple LDPC code, the coding gain is greatly improved, which provides a solution for the reliable transmission of information. Finally, the realization process of Raptor-LDPC code on DSP is described, which involves fixed-point quantization, matrix storage, matrix operation, etc. The effects of different quantization schemes and quantization stages on the performance of Raptor-LDPC code are discussed. It is found that the loss caused by quantization can be reduced to a very low level and the effect on the performance of concatenated codes can be reduced by choosing the appropriate quantization scheme. Through theoretical research and practical simulation, it can be found that the concatenation of LDPC codes and fountain codes not only has excellent codeword performance, but also keeps low encoding and decoding complexity. More importantly, it abandons the traditional automatic feedback retransmission (ARQ) mechanism. It can greatly shorten the transmission delay of the file and ensure the successful decoding rate at the same time. It can be used in the environment of deep space communication, deep-sea long-distance underwater acoustic communication and so on. It can effectively deal with the condition that the channel is time-varying, the transmission time is prolonged, the bit error rate is high, and the communication link is easy to be interrupted.
【學(xué)位授予單位】：杭州電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN911.22

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本文編號(hào)：2040698