移动通信中基于Turbo码的混合ARQ方案

在移动环境中，由于信道的时变特性，单纯的FEC或ARQ机制往往无法提供所希望的系统性能。为了提高数据及图像的传输可靠性，需采用ARQ与FEC相结合的混合ARQ差错控制方案。首先介绍了几种常见的以Turbo码作为纠错码的混合ARQ方案，然后研究了基于Turbo码组合译码的有限次重传混合ARQ方案，给出了传输方案及组合译码算法。仿真结果表明，低Eb/No时，该方案对通过率有明显改善。     

RCPT码的性能分析及其在混合ARQ中的应用研究

该文研究基于速率兼容的删余Turbo(RCPT)码的混合ARQ系统性能分析问题,提出将删余卷积码的网格图看成时变的网格图,并利用紧致界分析RVPT码的误帧率性能,进而计算RCPT-ARQ系统通过效率下界。经比较,理论分析结果与仿真结果十分吻合。     

一种用于分组数据可靠传输的Ⅱ型混合ARQ方法

本文基于码率匹配截短Turbo码和“码字校验交替重传”方案，提出了一种新的Ⅱ型混合ARQ方法，并将其应用于移动通信系统的分组数据业务中。仿真结果和分析表明，综合系统性能和复杂性两方面考虑，该方法不失为一种实现分组数据可靠传输的最佳解决方案。     

基于RCPT编码的自适应选择合并混合ARQ算法

混合自动重传请求（ARQ）作为一种差错控制技术被采纳为3GPP长期演进项目（LTE）的关键技术。基于速率兼容截断Turbo（RCPT）编码的混合ARQ算法,因其性能优异、实现复杂度低而被广泛关注。传统混合ARQ算法主要包括Chase合并方式混合ARQ,其在高信噪比条件下提供较大的性能增益;以及增量冗余（IR）方式混合ARQ,其在低信噪比条件下提供了更精确的速率控制。本文结合现有方法提出了一种基于RCPT编码的自适应选择合并混合ARQ算法,它在不同信噪比条件下自适应地选择Chase合并方式混合ARQ与IR方式混合ARQ,并且在接收端自适应地选择合并可靠性较高的传输码块。本文对其在瑞利衰落信道中的性能作了理论分析,并且进行了仿真,同时与传统的Chase合并方式混合ARQ以及IR方式混合ARQ作了性能比较。比较结果显示本文的算法在瑞利信道中比传统算法具有更为优异的性能以及相似的复杂度。     

半速率可逆RS码在流星突发系统中的应用

在流星突发通信中,可以采用好的编码技术来提高系统的吞吐量性能.针对流星突发信道的特点,提出了一种基于半速率可逆RS码的混合Ⅱ型ARQ,并对其性能进行了分析,给出了吞吐量的性能公式.从仿真结果可以看出,同已有的基于传统RS码的混合Ⅱ型ARQ相比,这种应用半速率可逆码的混合Ⅱ型ARQ可以使吞吐量性能获得较大的提高.     

基于LDPC码的可变冗余混合ARQ研究

在数字通信系统中,可变冗余混合ARQ方案既能提供通信的吞吐率,又能提高通信的可靠性。根据可变冗余混合ARQ方案的特性,本文设计了一种适合于可变冗余混合ARQ方案的LDPC码。仿真结果证明了基于LDPC码的可变冗余混合ARQ方案的良好性能。     

一种基于递归系统卷积码校验重量下限的匹配交织器设计方法

针对短帧Turbo码中交织器优化设计问题,提出了一种基于递归系统卷积码(RSC)校验重量下限的匹配交织器设计方法.文中重新分析了Turbo码中"局部坏点"具体形式,然后提出并证明了一种估计RSC分量码校验序列重量下限的方法,并将其应用于交织器映射方式优选时局部坏点对应Turbo码字重量下限估计,只有能够保证所有局部坏点对应码字重量的交织方法才被认为合法.仿真表明,与几种现有交织器设计方法相比,本文提出的匹配交织器设计方法性能更加优良,可以有效改善Turbo码的误比特性能.     

基于节点选择的Turbo编码协同ARQ协议

文中给出了一种基于节点选择的Turbo编码协同ARQ(TC-ARQ)协议方案,并从理论上证明了采用基于节点选择的TC-ARQ协议相比传统的Turbo ARQ协议(T-ARQ)能获得更高的分集增益以及比非节点选择的协同ARQ协议更低的误帧率.仿真结果证实了该方案相对T-ARQ的优异性能,并仿真分析了节点数对节点选择性能增益的影响.     

无线光通信差错控制系统的时间参数特性

在无线光通信系统中,光强闪烁和大气衰减等因素将使通信系统产生长突发误码,结合Turbo码,建议并分析了两种差错控制方案中时间参数的特性.对于Turbo码 信道交织的差错控制方案,仿真分析了不同信道交织深度下的无线光通信系统性能,给出了特性曲线.对于Turbo码 反馈重发(ARQ)的方案,仿真结果表明反馈环路延迟时间的变化不影响系统的平均吞吐量,但是将影响平均数据传输延迟和重发次数的概率分布.     

基于译码可靠度的混合ARQ方案中一种有效的反馈包压缩策略

相比传统的混合ARQ方案,基于译码可靠度的混合ARQ方案可以提供更好的性能.然而,该方案的一个致命缺陷在于反向链路的负载过大,尤其是选择turbo码作为纠错码时.本文提出了一种有效的反馈包压缩策略,充分利用了重传比特间的相对位置信息,可以有效地减小采用turbo码时反馈包过大的问题.仿真结果表明,通过对反馈包作压缩编码,大大减小了反馈包的大小,从而使基于译码可靠度的混合ARQ的实用成为可能.     

一种改进的不限重传次数的HARQ重传方案

为了保证数据在无线衰落信道条件下的可靠传输,产生了联合前向纠错编码(FEC)与自动请求重传(ARQ)的混合ARQ(HARQ)技术。HARQ有多种重传方案,本文针对HARQ的无限次重传方案进行了研究,提出了一种改进的基于RCPT码的HARQ重传方案,并分别与传统RCPT-HARQ方案在瑞利快衰落、慢衰落信道下进行仿真比较,仿真结果显示出改进方案在慢衰落信道条件下获得了更高的通过率。     

移动通信中基于Turbo码的H-ARQ技术

重点介绍了两种最近在3GPP和3GPP2中得到一定应用的H-ARQ技术:基于速率匹配短截Turbo码的H-ARQ技术,基于准互补Turbo码的H-ARQ技术等,主要分析了它们的基本原理和准则及实施方案;概述了基于其他编码的H-ARQ技术的研究情况.     

Separate codes on type-II hybrid ARQ systems

A hybrid automatic repeat request (ARQ) system (HARQ-II) with parity retransmission for error correction, which combines ARQ and forward error correction is discussed, and the successful application of these codes to HARG-II is illustrated. A method of constructing the codes whereby conventional BCH codes can be changed into separable codes is proposed. A scheme is presented that has the advantages that, the code lengths are always made equal and that even in parity retransmission new information symbols can be sent along with the necessary parity-check symbols. The performance of the proposed schemes on the binary symmetric channel is discussed. The numerical results show that they outperform conventional schemes     

MBC中的Ⅰ型HARQ改进方案

在流星突发通信中,为确保数据有效可靠地传输,通常采用前向纠错与自动重传请求相结合的方法,即HARQ。传统I型HARQ效率较低,难以满足大数据量通信。为了有效利用流星信道,建立了流星突发通信模型,提出了一种基于分集合并的Ⅰ型HARQ方案,推导出了有效信噪比公式,讨论了信噪比改善系数和最大重传次数,并进行了仿真。仿真结果表明,该方案可有效提高可靠性,增加吞吐量。     

基于校正子的第一类混合ARQ及其性能分析

基于校正子的计算提出了一种第一类混合ARQ (HARQ) 方案,该HARQ采用Reed-Solomon (RS)码作为纠错子系统,将检错功能巧妙融于译码过程中。对系统误比特率和吞吐量的分析与仿真表明,短码宜采用前向校正子结构,长码宜采用后向校正子结构,而系统的吞吐量与可靠性之间的最佳折衷,可以通过选择恰当的最大重传次数实现。     

Hybrid-ARQ scheme using different TCM for retransmission

A new hybrid automatic repeat-request (ARQ) scheme that uses supplementary trellis codes for retransmission is described. In this scheme, supplementary codes are designed to compensate for the squared free distance (d/sub free//sup 2/) of the trellis code used for the previous transmission. Differently encoded codewords are combined and decoded by the same Viterbi decoder at the receiver. This scheme provides improved (d/sub free//sup 2/) upon retransmission compared with that provided by the conventional trellis coded hybrid-ARQ scheme where the same coding scheme is used for all transmissions.     

Cross-layered retransmission schemes for TCP-based services

Various retransmission schemes for wireless communication systems have been used to improve performance such as reliability and throughput. Each retransmission scheme is designed to improve the performance according to characteristics of each layer of protocol stacks, such as delay components and error control. Especially, a cross-layered retransmission scheme has been proposed to maximize the spectral efficiency by combining a retransmission scheme and adaptive modulation and coding (AMC). However, the cross-layered retransmission scheme is designed for performance improvement at the wireless access networks. The end-to-end performance is not taken into account for modeling of the cross-layered retransmission schemes. It is difficult to design retransmission schemes for the end-to-end performance improvement. In this paper, we analyze the delay and the throughput at the transport layer for the end-to-end performance when a system uses a cross-layered retransmission scheme and the transmission control protocol as the reliable transmission protocols. We also propose a cross-layered retransmission strategy, AMC combined with automatic repeat request (ARQ) and hybrid ARQ (HARQ), to improve end-to-end throughput. From the evaluation results, it is shown that the proposed cross-layered retransmission strategy is suitable for delay insensitive services that require high throughput.     

Performance Modeling of the Fast and Reliable Two-Layer Retransmission for CDMA Systems

1　Introduction　With the proliferation of the World Wide Web (WWW)in our daily life, a number of wireless data services[1] suchas voice, audio, video streaming, file and web downloadingalso need to be supported in the wireless access networks.To bring the WWW traffic to the wireless mobile devices, itis important that a suitable protocol or standard is chosen tocater to the growing demands of data services over wirelesschannels which could handle a wide variety of multimediatraffic with …     

Parity retransmission hybrid ARQ using rate 1/2 convolutional codeson a nonstationary channel

A parity retransmission hybrid automatic repeat request (ARQ) scheme is proposed which uses rate 1/2 convolutional codes and Viterbi decoding. A protocol is described which is capable of achieving higher throughputs than previously proposed parity retransmission schemes. The performance analysis is based on a two-state Markov model of a nonstationary channel. This model constitutes a first approximation to a nonstationary channel. The two-state channel model is used to analyze the throughput and undetected error probability of the protocol presented when the receiver has both an infinite and a finite buffer size. It is shown that the throughput improves as the channel becomes more bursty