具有不等差错保护特性的喷泉码设计研究
发布时间：2018-11-04 12:39
【摘要】：随着移动通信和Internet网络等技术的发展,多媒体传输已日渐成为未来通信的主要业务。然而,在通信过程中,高丢包率、信道的时变特性以及终端的异构性严重限制了多媒体的传输,降低了通信的可靠性。因此,在传输过程中,如何降低图像、音频和视频等数据的误码率,减少对用户接收性能的影响,已成为多媒体通信研究的关键问题之一。数字喷泉码(Digital Fountain Codes)作为一种新的前向纠错编码(Forward Error Correction, FEC)技术,因为具有很多优越特性(如无码率特性、低编译码复杂度以及不需要反馈信息),已引起了编码界科研人员的广泛关注和深入研究。本文首先介绍了普通数字喷泉码(LT码和Raptor码)和其他具有不等差错保护(Unequal Error Protect on, UEP)特性的喷泉码的研究现状及特点,然后分别从渐进分析和实际仿真角度研究影响数字喷泉码的主要因素,并比较分析了现有几种常见的UEP喷泉码的优缺点。针对重复UEP LT码编译码复杂度高且UEP特性不明显等问题,本文提出了一种新颖的UEP喷泉码,基本思想是：采用低密度奇偶校验(Low-density Parity-check, LDPC)码代替重复UEP方案中的重复(Repeat)过程,并用具有高中间符号恢复率(Intermediate Symbol Recovery Rate, ISRR)的度分布取代高复杂度的鲁棒孤波分布(Robust Soliton Distribution, RSD)。首先,本文分别从渐近分析和实际仿真角度验证了：在重复UEP方案以及本文提出的UEP方案中,当采用具有常数平均度的度分布时,不能通过增大扩展因子(Expanding Factor)来改善性能。渐进分析和实际仿真进一步显示：在译码性能相同的条件下,相比于其他UEP方案,本文提出的UEP方案具有较低的复杂度；此外,本文提出的UEP方案能够获得较好的抗误码性能,在较小的输入信息长度下性能改善更加明显。峰值信噪比(Peak Signal-Noise Ratio, PSNR)性能仿真结果显示,在中等输入信息长度下,本文提出的UEP方案仅需要较小的译码开销就能获得很好的基本视频质量。数字喷泉码因为具有无码率特性,不需要反馈也能获得很好的性能。但在互联网以及移动通信网等网络中,因为双工通信的设计特点,反馈信道很容易获取,且传输少量的反馈信息不会对通信造成很大的影响。因此,本文通过单次引入单比特反馈信息,提出一种基于反馈的扩展窗喷泉(Expanding Window Fountain, EWF)码,分析研究了反馈对EWF码译码性能的影响。其次,本文还提出了一种实用预测模型来分别计算在普通EWF码以及本文提出的带反馈EWF码中成功恢复各重要等级数据符号需要的平均译码开销。渐进分析和仿真结果显示,与普通EWF码相比,本文提出的带反馈EWF码仅需要较小的译码开销就能完全恢复LIB数据。同时,结果也验证了本文提出的预测模型是有效的。
[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.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：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.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN911.2
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