无线ATM系统的混合纠错方案及其在突发信道上的性能分析

本文提出了一种适用于无线ＡＴＭ系统的混合纠错方案：用ＲＳ码保护语音信号,用截短ＲＳ／混合Ⅱ型ＡＲＱ保护图像和数据。文中分析和仿真了这一混合纠错方案在突发信道上的性能。结果表明,利用ＲＳ码强的纠错能力,通过有限次的重传就可获得低的信元丢失率和传输时延。     

二维RS乘积码的设计及FPGA实现

RS码具有很强的纠正突发错误的能力,因此广泛应用于无线通信。乘积码进行交织将错误分散,在内码中产生了大量随机错误,这使内码采用RS码纠错效果变得不明显。本文介绍了一种交织方案,极大提高了内码的纠错能力。并采用迭代译码构成了二维RS乘积码。当信道BER=2 99×10-3时, 经过FEC系统纠错译码后BER=0.838×10-7。     

RS码类的构建及在数据链模拟系统中的应用

Reed-Solomon码(RS码)具有强大的纠错能力,在数据通信中得到了广泛的应用,如RS(31,15)码已经成为美军数据链系统的标准码。为了实现应用于数据链模拟系统中的RS编译码类,从分析RS纠错编译码原理入手,在研究了RS编译码模型的基础上,重点对RS编译码的编程实现方法进行了详细分析。以VC++为编程实现平台,采用面向对象的程序设计方法,构建且封装了RS编译码类,最后对RS编译码类的纠错性能进行了验证,结果表明,设计的RS编译码类能够有效纠错且正确恢复发端发送的信息,满足模拟系统的设计要求。     

用于卫星链路的自适应级联码研究

在Ka频段卫星通信系统中,自适应纠错编码是一种很好的抗衰减措施。本文首先分析了抗衰减措施对自适应纠错编码的要求,提出了用RS码作外码、基于1／2卷积码的可变码率收缩码作内码加交织器构造自适应级联码,并对其原理和性能进行了详细分析。仿真表明该自适应级联码编码增益变化范围可达3～12dB以上,适用于卫星下行链路的自适应纠错编码抗衰减对策。     

基于无线光通信的增强型FEC研究

根据无线光通信信道的特点,提出了一种改进的EFEC(Enhanced FEC)级联码构造结构--外码+外交织器+内码+内交织器.在这种改进的结构下,研究了RS级联码在无线光通信信道中的纠错性能,以及交织器在级联码中对纠错性能的影响.得到了一种适合于无线光通信信道的高编码增益的级联码方案--RS(255,239)+外交织器+RS(31,21)+内交织器,编码增益改善了2～16dB.     

(16,12) RS缩短码编译码原理及性能分析

在各类数字通信系统以及计算机存储和运算系统经常利用差错控制编码降低误码率,提高通信质量,满足对数据传输通道可靠性的要求. RS 码是一种性能优良的前向纠错码,具有同时纠正随机错误和突发错误的能力,它的构造特点决定了其非常适合于纠正突发性错误.文中在阐述 RS 系统码编译码原理的基础上,提出了(16,12)RS 缩短码的编译码方法,利用 MATLAB 对(16,12)RS 缩短码在高斯信道和瑞利信道条件下的纠错能力进行仿真,并分析其纠错性能     

纠错编码技术在移动通信中的应用

针对移动通信中误码分布的特点,本文设计了一种差错控制方案,采用符号交织的方法使突发错误离散,再用RS(31,19)码进行纠错。计算机模拟结果表明,本方案优于Eurocom建议的方案。最后讨论了该方案的软硬件混合实现,在全变换域上实现了RS(31,19)码的译码。     

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。     

RS与卷积级联码在Rice信道中的性能分析

针对Rice信道的特性,采用RS码与卷积码进行级联的纠错编码方案,使用matlab对其在Rice信道上的纠错性能进行仿真分析。结果表明,在Rice信道上,RS和卷积的级联码是一种易于实现且性能优越高效的纠错码,有较高的实用价值。     

一种适用于高速无源光网络的前向纠错码

分析了无源光网络(PON)系统对前向纠错(FEC)的要求,并对现有FEC码型的纠错性能、冗余度和实现复杂度进行了分析比较,提出了一种适用于无源光网络的RS(255,239) BCH(1108,1020)级联码方案.仿真结果表明该码在编码增益、冗余度等方面具有较大的优势,且硬件实现简单,可作为下一代高速无源光网络中前向纠错码的候选码型.     

Performance of H.263 video transmission over wireless channelsusing hybrid ARQ

This paper proposes a hybrid ARQ error control scheme based on the concatenation of a Reed-Solomon (RS) code and a rate compatible punctured convolutional (RCPC) code for low-bit-rate video transmission over wireless channels. The concatenated hybrid ARQ scheme we propose combines the advantages of both type-I and type-II hybrid ARQ schemes. Certain error correction capability is provided in each (re)transmitted packet, and the information can be recovered from each transmission or retransmission alone if the errors are within the error correction capability (similar to type-I hybrid ARQ). The retransmitted packet contains redundancy bits which, when combined with the previous transmission, result in a more powerful RS/convolutional concatenated code to recover information if error correction fails for the individual transmissions (similar to type-II hybrid ARQ). Bit-error rate (BER) or signal-to-noise ratio (SNR) of a radio channel changes over time due to mobile movement and fading. The channel quality at any instant depends on the previous channel conditions. For the accurate analysis of the performance of the hybrid ARQ scheme, we use a multistate Markov chain (MSMC) to model the radio channel at the data packet level. We propose a method to partition the range of the received SNR into a set of states for constructing the model so that the difference between the error rate of the real radio channel and that of the MSMC model is minimized. Based on the model, we analyze the performance of the concatenated hybrid ARQ scheme. The results give valuable insight into the effects of the error protection capability in each packet, the mobile speed, and the number of retransmissions. Finally, the transmission of H.263 coded video over a wireless channel with error protection provided by the concatenated hybrid ARQ scheme is studied by means of simulations     

Non‐binary type‐II HARQ and its application to an adaptive system

Non‐binary type‐II hybrid ARQ (HARQ), which combines shortened Reed–Solomon (RS) code with ARQ, is proposed. Its throughput is obtained by extending Lin and Yu's analysis of binary type‐II HARQ. The reliability and average delay are also obtained. The analytical results show that non‐binary HARQ outperforms its binary counterpart in throughput, reliability and average delay when proper RS codes are selected. Non‐binary HARQs are applied adaptively in a cellular phone system with uniformly distributed mobile terminals (MTs). MTs switch adaptively between two different hybrid schemes according to the average SNR of the received signals. The adaptive parameters include the size of the modulation constellation, the error‐correction coding and their joint adaptation. Numerical results show that the adaptive scheme always outperforms its non‐adaptive counterparts, and the adaptive modulation scheme is superior to adaptive coding and the joint adaptation scheme when the implementation complexity is a limiting factor. Robustness analysis shows that introducing a mixed modulation scheme in addition to QPSK and 8PSK in the adaptive modulation scheme is unnecessary, and HARQ with adaptive modulation is insensitive to deviations from the optimal threshold, thus facilitating its implementation. Copyright © 2004 John Wiley & Sons, Ltd.     

An error control system with multiple-stage forward errorcorrections

A robust error control coding system is presented. This system is a cascaded FEC (forward error control) scheme supported by parity retransmissions for further error correction in the erroneous data words. The error performance and throughput efficiency of the system are analyzed. Two specific examples of the error control system are studied. The first example does not use an inner code, and the outer code, which is not interleaved, is a shortened code of the NASA standard RS code over GF(2⁸). The second example, as proposed for NASA uses the same shortened RS code as the base outer code C₂, except that it is interleaved to a depth of 2. It is shown that both examples provide high reliability and throughput efficiency even for high channel bit-error rates in the range of 10^-2     

A novel RS BTC coding scheme for optical communications

A novel Reed Solomon(RS) block turbo code(BTC) coding scheme of RS(63,58)×RS(63,58) for optical communications is proposed.The simulation results show that the net coding gain(NCG) of this scheme at the sixth iteration is more than that of other coding schemes at the third iteration for the bit error rate(BER) of 10-12.Furthermore,the novel RS BTC has shorter component code and rapider encoding and decoding speed.Therefore,the novel RS BTC coding scheme can be better used in high-speed long-haul optical communication systems,and the novel RS BTC can be regarded as a candidate code of the super forward error correction(super-FEC) code.Moreover,the encoding/decoding design and implementation of the novel RS BTC are also presented.     

Robust VB 2D-CELP image transmission over CDMA Rayleigh fading channels

This paper describes a new error resilient analysis-by-synthesis coding scheme and its application for robust still image transmission over CDMA Rayleigh fading channels. For the purpose of providing reliable transmission, a type-I hybrid ARQ protocol is used in a concatenated Reed–Solomon/convolutional coding scheme. However, for delay-constrained applications, the protocol is used with a limited number of retransmissions in addition to limited RS interleaving. Results of coded images are provided for the uplink of a communication system, where a slowly Rayleigh fading channel is considered.     

Error concealment aware rate shaping for wireless video transport

Streaming of video, which is both source- and channel-coded, over wireless networks faces the challenge of time-varying packet loss rate and fluctuating bandwidth. Rate shaping (RS) has been proposed to reduce the bit-rate of a precoded video bitstream to adapt to the real-time bandwidth variation. In our earlier work, rate shaping was extended to consider not only the bandwidth but also the packet loss rate variations. Rate-distortion optimized rate adaptation is performed on the precoded video that is a scalable coded bitstream protected by forward error correction codes. In this paper, we propose an RS scheme that further takes into account the error concealment (EC) method used at the receiver. We refer to this scheme as EC aware RS (ECARS). When performing ECARS, first ECARS needs to know the benefit/gain of sending each part of the precoded video, as opposed to not sending it but reconstructing it by EC. Then given a certain packet loss probability, the expected gain can be derived and be included in the rate-distortion optimization problem formulation. Finally, ECARS performs rate-distortion optimization to adapt the rate of the precoded video. A two-stage rate-distortion optimization approach is proposed to solve the ECARS rate-distortion optimization problem. In addition to ECARS, the precoding process can be EC aware to prioritize the precoded video based on the gain. We present an example EC aware precoding process by means of macroblock prioritization. Experiment results of ECARS together with EC aware precoding are shown to have excellent performance.     

A novel adaptive hybrid ARQ scheme for wireless ATM networks

This paper describes the design and performance of a novel adaptive hybrid ARQ scheme using concatenated FEC codes for error control over wireless ATM networks. The wireless links are characterized by higher, time‐varying error rates and burstier error patterns in comparison with the fiber‐based links for which ATM was designed. The purpose of the hybrid ARQ scheme is to provide a capability to dynamically support reliable ATM‐based transport over wireless channels by using a combination of our ARQ scheme (called SDLP) and the concatenated FEC scheme. The key ideas in the proposed hybrid ARQ scheme are to adapt the code rate to the channel conditions using incremental redundancy and to increase the starting code rate as much as possible with the concatenated FEC, maximizing the throughput efficiency. The numerical results show that our proposed scheme outperforms other ARQ schemes for all SNR values. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multilevel RS/convolutional concatenated coded QAM for hybridIBOC-AM broadcasting

Bandwidth efficient modulation schemes using Reed-Solomon (RS) codes are proposed for hybrid in-band-on-channel (IBOC) systems that broadcast digital audio signals simultaneously with analog amplitude modulation (AM) programs in the AM band. Since both the power and bandwidth allocated for digital audio transmission are limited in this application, the system cannot afford to add enough redundancy for error control using conventional concatenated coding schemes. We show that by using multilevel RS and convolutional concatenated coded quadrature amplitude modulation (QAM), an efficient modulation schemes can be obtained for applications such as IBOC-AM broadcasting     

Improved Error Control for Real-Time Video Broadcasting Over CDMA2000 Networks

The broadcast and multicast services (BCMCS) protocol is designed for real-time applications such as MPEG-4 video streaming, which requires successive frames to arrive within a specific time interval. We analyze the execution time of Reed-Solomon (RS) decoding, which is the medium access control (MAC)-layer forward error-correction (FEC) scheme used in CDMA2000 1xEV-DO BCMCS, under various air channel conditions. The results show that the timing constraints of MPEG-4 cannot always be met by RS decoding when the packet loss rate (PLR) is high, due to the limited processing power of current hardware. We therefore propose three error control schemes: First, we have our static scheme, which bypasses RS decoding at the mobile node to satisfy the MPEG-4 timing constraint when the PLR exceeds a given level. Second, we have the dynamic scheme, which corrects as many errors as possible within the timing constraint, instead of giving up altogether when the PLR is high; this improves quality. Third, we have the video-aware dynamic scheme, which fixes errors in a similar way to the dynamic scheme but in a priority-driven manner, yielding a further increment in video quality at mobile terminals. Extensive simulation results show the effectiveness of our schemes compared with the original FEC scheme.     

Energy‐Aware Hybrid Cooperative Relaying with Asymmetric Traffic

In this paper, we study an asymmetric two‐way relaying network where two source nodes intend to exchange information with the help of multiple relay nodes. A hybrid time‐division broadcast relaying scheme with joint relay selection (RS) and power allocation (PA) is proposed to realize energy‐efficient transmission. Our scheme is based on the asymmetric level of the two source nodes’ target signal‐to‐noise ratio indexes to minimize the total power consumed by the relay nodes. An optimization model with joint RS and PA is studied here to guarantee hybrid relaying transmissions. Next, with the aid of our proposed intelligent optimization algorithm, which combines a genetic algorithm and a simulated annealing algorithm, the formulated optimization model can be effectively solved. Theoretical analyses and numerical results verify that our proposed hybrid relaying scheme can substantially reduce the total power consumption of relays under a traffic asymmetric scenario; meanwhile, the proposed intelligent optimization algorithm can eventually converge to a better solution.