具有不等差錯保護(hù)特性的噴泉碼設(shè)計研究
發(fā)布時間：2018-11-04 12:39
【摘要】：隨著移動通信和Internet網(wǎng)絡(luò)等技術(shù)的發(fā)展,多媒體傳輸已日漸成為未來通信的主要業(yè)務(wù)。然而,在通信過程中,高丟包率、信道的時變特性以及終端的異構(gòu)性嚴(yán)重限制了多媒體的傳輸,降低了通信的可靠性。因此,在傳輸過程中,如何降低圖像、音頻和視頻等數(shù)據(jù)的誤碼率,減少對用戶接收性能的影響,已成為多媒體通信研究的關(guān)鍵問題之一。數(shù)字噴泉碼(Digital Fountain Codes)作為一種新的前向糾錯編碼(Forward Error Correction, FEC)技術(shù),因為具有很多優(yōu)越特性(如無碼率特性、低編譯碼復(fù)雜度以及不需要反饋信息),已引起了編碼界科研人員的廣泛關(guān)注和深入研究。本文首先介紹了普通數(shù)字噴泉碼(LT碼和Raptor碼)和其他具有不等差錯保護(hù)(Unequal Error Protect on, UEP)特性的噴泉碼的研究現(xiàn)狀及特點(diǎn),然后分別從漸進(jìn)分析和實際仿真角度研究影響數(shù)字噴泉碼的主要因素,并比較分析了現(xiàn)有幾種常見的UEP噴泉碼的優(yōu)缺點(diǎn)。針對重復(fù)UEP LT碼編譯碼復(fù)雜度高且UEP特性不明顯等問題,本文提出了一種新穎的UEP噴泉碼,基本思想是：采用低密度奇偶校驗(Low-density Parity-check, LDPC)碼代替重復(fù)UEP方案中的重復(fù)(Repeat)過程,并用具有高中間符號恢復(fù)率(Intermediate Symbol Recovery Rate, ISRR)的度分布取代高復(fù)雜度的魯棒孤波分布(Robust Soliton Distribution, RSD)。首先,本文分別從漸近分析和實際仿真角度驗證了：在重復(fù)UEP方案以及本文提出的UEP方案中,當(dāng)采用具有常數(shù)平均度的度分布時,不能通過增大擴(kuò)展因子(Expanding Factor)來改善性能。漸進(jìn)分析和實際仿真進(jìn)一步顯示：在譯碼性能相同的條件下,相比于其他UEP方案,本文提出的UEP方案具有較低的復(fù)雜度；此外,本文提出的UEP方案能夠獲得較好的抗誤碼性能,在較小的輸入信息長度下性能改善更加明顯。峰值信噪比(Peak Signal-Noise Ratio, PSNR)性能仿真結(jié)果顯示,在中等輸入信息長度下,本文提出的UEP方案僅需要較小的譯碼開銷就能獲得很好的基本視頻質(zhì)量。數(shù)字噴泉碼因為具有無碼率特性,不需要反饋也能獲得很好的性能。但在互聯(lián)網(wǎng)以及移動通信網(wǎng)等網(wǎng)絡(luò)中,因為雙工通信的設(shè)計特點(diǎn),反饋信道很容易獲取,且傳輸少量的反饋信息不會對通信造成很大的影響。因此,本文通過單次引入單比特反饋信息,提出一種基于反饋的擴(kuò)展窗噴泉(Expanding Window Fountain, EWF)碼,分析研究了反饋對EWF碼譯碼性能的影響。其次,本文還提出了一種實用預(yù)測模型來分別計算在普通EWF碼以及本文提出的帶反饋EWF碼中成功恢復(fù)各重要等級數(shù)據(jù)符號需要的平均譯碼開銷。漸進(jìn)分析和仿真結(jié)果顯示,與普通EWF碼相比,本文提出的帶反饋EWF碼僅需要較小的譯碼開銷就能完全恢復(fù)LIB數(shù)據(jù)。同時,結(jié)果也驗證了本文提出的預(yù)測模型是有效的。
[Abstract]:With the development of mobile communication and Internet network, multimedia transmission has become the main service of future communication. However, in the process of communication, the high packet loss rate, the time-varying characteristics of the channel and the heterogeneity of the terminal seriously limit the transmission of multimedia and reduce the reliability of communication. Therefore, how to reduce the bit error rate (BER) of image, audio and video and how to reduce the impact on the performance of users has become one of the key problems in multimedia communication. Digital fountain code (Digital Fountain Codes) is a new forward error correction coding (Forward Error Correction, FEC) technology, because of its many advantages (such as no bit rate, low encoding and decoding complexity and no need for feedback information). It has aroused the extensive attention and in-depth research of the researchers in the field of coding. This paper first introduces the research status and characteristics of ordinary digital fountain codes (LT codes and Raptor codes) and other fountain codes with unequal error protection (Unequal Error Protect on, UEP) characteristics. Then the main factors affecting digital fountain codes are studied from the point of view of evolutionary analysis and actual simulation, and the advantages and disadvantages of several common UEP fountain codes are compared and analyzed. Aiming at the problems of high complexity and low UEP characteristics of repeated UEP LT codes, a novel UEP fountain code is proposed in this paper. The basic idea is to adopt low density parity check (Low-density Parity-check,). LDPC) code replaces the repeated (Repeat) process in the repetitive UEP scheme and replaces the robust solitary wave distribution (Robust Soliton Distribution, RSD). With high complexity with the degree distribution with high intermediate symbol recovery rate (Intermediate Symbol Recovery Rate, ISRR). Firstly, from the point of view of asymptotic analysis and actual simulation, it is verified that in the repeated UEP scheme and the UEP scheme proposed in this paper, when the degree distribution with constant average degree is adopted, the performance can not be improved by increasing the expansion factor (Expanding Factor). The asymptotic analysis and actual simulation show that the proposed UEP scheme has lower complexity compared with other UEP schemes under the same decoding performance; In addition, the proposed UEP scheme can achieve better error-resistant performance, and the performance improvement is more obvious when the input information length is smaller. The simulation results of peak signal-to-noise ratio (Peak Signal-Noise Ratio, PSNR) performance show that the proposed UEP scheme can achieve good basic video quality only with small decoding overhead under the medium input information length. Digital fountain code can get good performance without feedback because it has no bit rate characteristics. However, in the Internet and mobile communication networks, the feedback channel is easy to obtain because of the design characteristics of duplex communication, and the transmission of a small amount of feedback information will not have a great impact on the communication. Therefore, by introducing single bit feedback information, this paper presents an extended window fountain (Expanding Window Fountain, EWF) code based on feedback, and analyzes the effect of feedback on the decoding performance of EWF codes. Secondly, a practical prediction model is proposed to calculate the average decoding overhead required for the successful restoration of important data symbols in the ordinary EWF codes and the EWF codes with feedback proposed in this paper. The asymptotic analysis and simulation results show that compared with ordinary EWF codes, the proposed EWF codes with feedback can completely recover LIB data with less decoding overhead. At the same time, the results show that the proposed prediction model is effective.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TN911.2
[Abstract]:With the development of mobile communication and Internet network, multimedia transmission has become the main service of future communication. However, in the process of communication, the high packet loss rate, the time-varying characteristics of the channel and the heterogeneity of the terminal seriously limit the transmission of multimedia and reduce the reliability of communication. Therefore, how to reduce the bit error rate (BER) of image, audio and video and how to reduce the impact on the performance of users has become one of the key problems in multimedia communication. Digital fountain code (Digital Fountain Codes) is a new forward error correction coding (Forward Error Correction, FEC) technology, because of its many advantages (such as no bit rate, low encoding and decoding complexity and no need for feedback information). It has aroused the extensive attention and in-depth research of the researchers in the field of coding. This paper first introduces the research status and characteristics of ordinary digital fountain codes (LT codes and Raptor codes) and other fountain codes with unequal error protection (Unequal Error Protect on, UEP) characteristics. Then the main factors affecting digital fountain codes are studied from the point of view of evolutionary analysis and actual simulation, and the advantages and disadvantages of several common UEP fountain codes are compared and analyzed. Aiming at the problems of high complexity and low UEP characteristics of repeated UEP LT codes, a novel UEP fountain code is proposed in this paper. The basic idea is to adopt low density parity check (Low-density Parity-check,). LDPC) code replaces the repeated (Repeat) process in the repetitive UEP scheme and replaces the robust solitary wave distribution (Robust Soliton Distribution, RSD). With high complexity with the degree distribution with high intermediate symbol recovery rate (Intermediate Symbol Recovery Rate, ISRR). Firstly, from the point of view of asymptotic analysis and actual simulation, it is verified that in the repeated UEP scheme and the UEP scheme proposed in this paper, when the degree distribution with constant average degree is adopted, the performance can not be improved by increasing the expansion factor (Expanding Factor). The asymptotic analysis and actual simulation show that the proposed UEP scheme has lower complexity compared with other UEP schemes under the same decoding performance; In addition, the proposed UEP scheme can achieve better error-resistant performance, and the performance improvement is more obvious when the input information length is smaller. The simulation results of peak signal-to-noise ratio (Peak Signal-Noise Ratio, PSNR) performance show that the proposed UEP scheme can achieve good basic video quality only with small decoding overhead under the medium input information length. Digital fountain code can get good performance without feedback because it has no bit rate characteristics. However, in the Internet and mobile communication networks, the feedback channel is easy to obtain because of the design characteristics of duplex communication, and the transmission of a small amount of feedback information will not have a great impact on the communication. Therefore, by introducing single bit feedback information, this paper presents an extended window fountain (Expanding Window Fountain, EWF) code based on feedback, and analyzes the effect of feedback on the decoding performance of EWF codes. Secondly, a practical prediction model is proposed to calculate the average decoding overhead required for the successful restoration of important data symbols in the ordinary EWF codes and the EWF codes with feedback proposed in this paper. The asymptotic analysis and simulation results show that compared with ordinary EWF codes, the proposed EWF codes with feedback can completely recover LIB data with less decoding overhead. At the same time, the results show that the proposed prediction model is effective.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TN911.2
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