BIAWGN信道下的扩展窗喷泉码设计研究
发布时间：2019-01-10 12:56
【摘要】：随着无线通讯技术的迅猛发展和网络带宽的不断提高,多媒体传输正日渐成为通信行业的主干业务。然而,在实际通信过程中,高丢包率以及信道的非理想性等严重降低了信息传输的可靠性。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,不同于具有固定码率的传统的纠错方案,其凭借无码率,无需反馈重传,编译码复杂度低等优点,在恶劣的信道中都能保证数据的高质量传输,因此成为了编码界的研究热点。针对多媒体应用中重要等级不同的数据需要不等水平保护的情景,本论文以具有不等差错保护(Unequal Error Protection, UEP )特性的扩展窗喷泉(Expanding Window Fountain, EWF)码的编码和调制算法为研究核心,提出了一种新颖的可适用于BIAWGN信道的UEP喷泉码。基本思想是:EWF码的错误平层主要是由度值很小的输入节点影响的,为了改善其性能,将EWF码编码过程进行了修改,最终使输入符号度值由泊松分布变成了具有两到三个度值的均匀分布。此外,由于EWF码的不同窗输出的符号经过编码之后具有不同的重要等级,因此可以加入不等功率分配(Unequal Power Allocation, UPA),进一步改善EWF码的UEP性能。为了验证提出方案的渐进性能,本文推导出了完整的外部信息转移(Extrinsic Information Transfer,EXIT)函数渐进分析公式,从渐进分析和实际仿真两个角度验证了规则的度分布可以很好的降低EWF码的错误平层,加入不等功率分配,在很大程度上进一步改善了更高等级比特的性能。基于Raptor码的思想,为了进一步消除错误平层,本文将高码率的LDPC码与新提出的EWF码结合构建了一种新的预编码EWF码。渐进分析和仿真结果显示,与传统预编码EWF码相比,本文新提出的EWF码译码性能有明显改善,并且具有更大灵活性。此外,通过联合优化新提出的预编码EWF码的编码参数和功率分配比例系数,可以使译码性能达到最佳。
[Abstract]:With the rapid development of wireless communication technology and the continuous improvement of network bandwidth, multimedia transmission is becoming the backbone of the communication industry. However, in the actual communication process, the high packet loss rate and channel non-ideal seriously reduce the reliability of information transmission. Digital fountain code (Digital Fountain Codes), as a new forward error correction coding (Forward Error Correction, FEC) technique, is different from the traditional error correction scheme with fixed bit rate. It has the advantages of no code rate, no need of feedback retransmission, and low coding and decoding complexity. In bad channels, high quality data transmission can be guaranteed, so it has become a research hotspot in coding field. In view of the situation that different important levels of data need unequal level protection in multimedia applications, this paper uses the extended window fountain (Expanding Window Fountain, with unequal error protection (Unequal Error Protection, UEP) characteristics. Based on the coding and modulation algorithms of EWF codes, a novel UEP fountain code for BIAWGN channels is proposed. The basic idea is: the error level of EWF code is mainly affected by the input node with very small degree. In order to improve its performance, the coding process of EWF code is modified. Finally, the input symbolic degree value is changed from Poisson distribution to uniform distribution with two to three degrees. In addition, because the symbols output from different windows of EWF codes have different important grades after encoding, (Unequal Power Allocation, UPA), with unequal power distribution can be added to further improve the UEP performance of EWF codes. In order to verify the asymptotic performance of the proposed scheme, a complete asymptotic analysis formula of the external information transfer (Extrinsic Information Transfer,EXIT) function is derived in this paper. From the point of view of asymptotic analysis and actual simulation, it is proved that the regular degree distribution can reduce the error level layer of EWF code and add unequal power allocation to further improve the performance of higher level bits. Based on the idea of Raptor code, in order to further eliminate the error level, this paper combines the high bit-rate LDPC code with the newly proposed EWF code to construct a new pre-coded EWF code. The asymptotic analysis and simulation results show that compared with the traditional precoded EWF codes, the new EWF codes proposed in this paper have better decoding performance and more flexibility. In addition, the decoding performance can be optimized by jointly optimizing the coding parameters and the power allocation ratio coefficients of the proposed precoded EWF codes.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN911.22
本文编号：2406340
[Abstract]:With the rapid development of wireless communication technology and the continuous improvement of network bandwidth, multimedia transmission is becoming the backbone of the communication industry. However, in the actual communication process, the high packet loss rate and channel non-ideal seriously reduce the reliability of information transmission. Digital fountain code (Digital Fountain Codes), as a new forward error correction coding (Forward Error Correction, FEC) technique, is different from the traditional error correction scheme with fixed bit rate. It has the advantages of no code rate, no need of feedback retransmission, and low coding and decoding complexity. In bad channels, high quality data transmission can be guaranteed, so it has become a research hotspot in coding field. In view of the situation that different important levels of data need unequal level protection in multimedia applications, this paper uses the extended window fountain (Expanding Window Fountain, with unequal error protection (Unequal Error Protection, UEP) characteristics. Based on the coding and modulation algorithms of EWF codes, a novel UEP fountain code for BIAWGN channels is proposed. The basic idea is: the error level of EWF code is mainly affected by the input node with very small degree. In order to improve its performance, the coding process of EWF code is modified. Finally, the input symbolic degree value is changed from Poisson distribution to uniform distribution with two to three degrees. In addition, because the symbols output from different windows of EWF codes have different important grades after encoding, (Unequal Power Allocation, UPA), with unequal power distribution can be added to further improve the UEP performance of EWF codes. In order to verify the asymptotic performance of the proposed scheme, a complete asymptotic analysis formula of the external information transfer (Extrinsic Information Transfer,EXIT) function is derived in this paper. From the point of view of asymptotic analysis and actual simulation, it is proved that the regular degree distribution can reduce the error level layer of EWF code and add unequal power allocation to further improve the performance of higher level bits. Based on the idea of Raptor code, in order to further eliminate the error level, this paper combines the high bit-rate LDPC code with the newly proposed EWF code to construct a new pre-coded EWF code. The asymptotic analysis and simulation results show that compared with the traditional precoded EWF codes, the new EWF codes proposed in this paper have better decoding performance and more flexibility. In addition, the decoding performance can be optimized by jointly optimizing the coding parameters and the power allocation ratio coefficients of the proposed precoded EWF codes.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN911.22
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