A synchronous digital hierachy based dynamic error correction technique for wavelength division multiplexing networks

This paper proposes a new synchronous digital hierarchy (SDH) based forward error correction (FEC) scheme for wavelength division multiplexing (WDM) networks. In this scheme, a dedicated WDM channel is used to transport the FEC redundant bits. This paper also proposes the use of error location analysis of the FEC correctable bits to identify the pattern of errors, combined with the seriousness of errors obtained from B2-byte analysis to decide as to the suitable FEC code to be assigned to the payload channels. The proposed FEC scheme is studied not only under the typical Poisson errors but also the bursty errors. Simulation results show that the proposed FEC scheme performs significantly better than the existing FEC schemes. It is also shown that the performance of the proposed FEC scheme on bursty errors is independent of the line rates, whereas the existing FEC schemes either cannot support bursty errors or degrades with line rates.     

Improved forward error correction technology of RS-LDPC cascade code in optical transport network

With the continuous development of optical communication and the increase in data transmission volume, optical transport network (OTN) has become the focus of research in next-generation transmission networks. In the process of data transmission, errors caused by noise often occur, resulting in an increase in the bit error rate (BER) and a decrease in the performance of the optical communication system. Therefore, we use forward error correction (FEC) technology in OTN for error control to improve the transmission efficiency of signals in OTN and reduce the BER. Standard FEC technology uses RS(255,239) code. On this basis, since the performance of low density parity check (LDPC) code is close to the Shannon limit, we propose a method of cascading RS code and LDPC code. Applying this improved FEC technology to OTN, the simulation results show that the improved FEC technology has a reduced BER compared with the standard FEC technology. When the BER is at the 10-3 level, the performance is improved by about 1.7 dB.     

WDM光传送网络中数字包封与前向纠错分析

为适应多种不同格式信号 (如 ATM、SDH、IP等 )透明传送的需要 ,高速 WDM光传送网络采用数字包封技术。按照 RS纠错码编码规则 ,采用相应的编码形式可纠正一定的突发误码。WDM光网络系统的 TDM数字包封采用 RS纠错码编码 FEC应用形式。分析了 TDM数字包封的基本原理及 RS纠错码编码 FEC的纠错性能特性。     

SDH中泊松分布下误块率与误码率的关系分析

本文较详细地介绍了ＳＤＨ中的ＢＩＰ误码校验方式，推导了泊松分布下，ＢＩＰ误块率与误码率的一般关系式，给出了ＳＤＨ中几种典型的误块率与误码率的关系曲线，并做了计算机模拟验证     

OTN中FEC的优化设计及实现

光信号在OTN中传输时不可避免地会产生误码,而传统的反馈重传纠错方式因为需要反馈信道和重传等待时间,所以不适合在传输速率较高的OTN中使用。因此利用RS码及数据交织方法,设计了OTN中的FEC电路,同时为了提高电路性能,对电路中常用的有限域乘法器进行了优化。并通过仿真和FPGA验证电路功能的正确性。实验结果表明,所设计的FEC电路能够纠正传输中出现的误码,满足OTN技术要求。     

Performance modeling of FEC‐based unequal error protection for H.264/AVC video streaming over burst‐loss channels

Unequal error protection systems are a popular technique for video streaming. Forward error correction (FEC) is one of error control techniques to improve the quality of video streaming over lossy channels. Moreover, frame‐level FEC techniques have been proposed for video streaming because of different priority video frames within the transmission rate constraint on a Bernoulli channel. However, various communication and storage systems are likely corrupted by bursts of noise in the current wireless behavior. If the burst losses go beyond the protection capacity of FEC, the efficacy of FEC can be degraded. Therefore, our proposed model allows an assessment of the perceived quality of H.264/AVC video streaming over bursty channels, and is validated by simulation experiments on the NS‐2 network simulator at a given estimate of the packet loss ratio and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide a more accurate evaluation tool for video streaming over bursty channels and help to evaluate the impact of FEC performance on different burst‐loss parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

Performance Parameters of ATM Networks with Bursts of Errors

In this paper we present the calculation of the error performance of a point-to-point ATM connection transported on an STS-3c SONET (SDH STM-1) interface. The ATM layer performance parameters calculated are Cell Loss Ratio (CLR), Cell Error Ratio (CER), and Severely Errored Cell Block Ratio (SECBR). Statistics of consecutive errored and lost cells are also calculated for each run of the simulation. The physical layer performance parameters such as Bit Error Ratio (BER), Errored Second Ratio (ESR), and Severely Errored Second Ratio (SESR) are compared with corresponding objective values in G.826. The bursty nature of errors in physical communication channels is described by the Hidden Markov Model (HMM) which is obtained from the experimental data. The importance of using this model is demonstrated by the simulation results. The ATM performance for channels with independent errors differs significantly from the ATM performance for channels with bursts of errors and equal bit error ratios.     

Estimation of the error performance objectives for satellite communication systems

We consider the physical layer error performance parameters and design criteria for digital satellite systems established by ITU‐R Recommendation S.1062, where the performance objectives are given in terms of the bit error rate (BER) divided by the average number of errors within a cluster. It is well known that errors on satellite links employing forward error correction (FEC) schemes tend to occur in clusters. The resulting block error rate is the same as if it was caused by randomly occurring bit errors with an error‐event ratio of BER/α, where α is the average number of errors within a cluster. The factor, α, accounts for the burstiness of the errors and also represents the ratio between the BER and the error‐event ratio. This paper proposes theoretical methods to estimate the factor, α. Using the weight distributions of the FEC codes, we derive a set of expressions for the factor, α, as well as their compact lower bounds. We present lower bounds for various FEC schemes including binary BCH codes, block turbo codes, convolutional codes, and turbo codes. The simulation results show that the proposed lower bounds are good estimates in the high signal‐to‐noise ratio region. Copyright © 2008 John Wiley & Sons, Ltd.     

吐哈油田融合网络规划与设计探讨

根据吐哈油田光传送网络的实际情况和建设智能油田的需要,通过对OTN技术和Ethernet技术的比较分析,提出DWDM+Ethernet比OTN技术更适合以IP数据业务和应用为主的网络,是吐哈油田下一代融合网络的最佳选择。给出了实际设计方案,方案采用了先进的前向纠错(FEC)技术解决现有光缆路由中存在的超长跨距和超大光衰耗导致的光信噪比(OSNR)低于网络技术指标要求的技术难题。     

OTN+MPLS-TP技术

通过与SDH技术对比,概述了光传送网(OTN)的优势所在.因此,SDH向OTN演进是光网络发展的一种必然趋势.介绍了OTN技术现状和MPLS-TP技术特点,指出"OTN+MPLS-TP"技术是光网络下一步发展的方向.     

Small‐block interleaving for low‐delay cross‐packet forward error correction over burst‐loss channels

By adding the redundant packets into source packet block, cross‐packet forward error correction (FEC) scheme performs error correction across packets and can recover both congestion packet loss and wireless bit errors accordingly. Because cross‐packet FEC typically trades the additional latency to combat burst losses in the wireless channel, this paper presents a FEC enhancement scheme using the small‐block interleaving technique to enhance cross‐packet FEC with the decreased delay and improved good‐put. Specifically, adopting short block size is effective in reducing FEC processing delay, whereas the corresponding effect of lower burst‐error correction capacity can be compensated by deliberately controlling the interleaving degree. The main features include (i) the proposed scheme that operates in the post‐processing manner to be compatible with the existing FEC control schemes and (ii) to maximize the data good‐put in lossy networks; an analytical FEC model is built on the interleaved Gilbert‐Elliott channel to determine the optimal FEC parameters. The simulation results show that the small‐block interleaved FEC scheme significantly improves the video streaming quality in lossy channels for delay‐sensitive video. Copyright © 2013 John Wiley & Sons, Ltd.     

40-Gbit/s ETDM Channel Technologies for Optical Transport Network

We review recent progress and the future of 40-Gbit/s electrical time division multiplexed (ETDM) channel technologies for the optical transport network (OTN), where optical technologies, including high-speed ETDM channel transmission and wavelength division multiplexing (WDM), dramatically enhance network flexibility while reducing transport node cost as well as transmission cost. The 40 Gbit/s channel has recently been specified to be one of the optical channels in OTN. A new digital frame for the optical channels [optical channel transport unit (OTU)] was introduced for the network node interface of OTN in International Telecommunication Union-Telecommunication (ITU-T) standard. The specified data bit rates are 2.7 Gbit/s (OTU1), 10.7 Gbit/s (OTU2), and 43.0 Gbit/s (OTU3). These OTU frames have additional overhead bytes that support the network management overhead for OTN and out-of-band forward error correcting (FEC) codes. We discuss the feasibility and impact of the OTU3 frame in terrestrial networks. A newly developed 43-Gbit/s OTN line terminal prototype that confirms the feasibility of 43-Gbit/s ETDM channels and the OTU3 management capability is discussed. As a guide to the evolution of OTN, modulation formats for 43Gbit/s-based DWDM transmission are described for long distance application with the total capacity over one terabit per second.     

Error recovery for ATM transmission over wireless channels

The authors present a technique for efficient recovery from transmission errors to be used when transmitting ATM-like data packets in a wireless channel affected by bursty errors (jamming). Issues related to packet format error protection code structure and retransmission protocol are discussed and simulation results are shown that prove the effectiveness of the proposed approach     

SDH光纤保密设备在光纤传送网中的应用

论文介绍了我国的SDH光纤传送网特点,针对光纤网面临的威胁,分析了SDH加密技术,提出了SDH保密设备的加密体制和手段以及在光纤传送网中的多种应用模式。     

OTN中FEC技术的应用

光传送网(OTN)是随着WDM技术的发展而产生的,ITU—T在2001年提出了其接口标准——G．709建议。该建议采用数字包封技术,定义了数据的封装格式,将前向纠错(FEC)技术引入光传送网标准接口中。文章分析了OTN的帧格式,着重介绍了其采用的FEC技术。将G.709标准应用到实际光接口盘的设计中,并通过实验验证了FEC技术的良好效果。     

Bursty Traffic Local Network Modeling

A computer program to predict the performance of local area networks based on an Ethernet or other medium is described. The effects of bursty traffic are modeled as packet streams which are initially bulk Poisson, but whose clusters spread apart as they propagate through the network. It is shown by example that performance predictions using more conventional Poisson assumptions tend to be optimistic, often extremely so. The program presents a friendly, dialogue-oriented user interface, including a library of rather sophisticated transaction types for network loading. A simulator is included in the program to validate its analytical approximations, and two example simulations are presented. Although approximation errors can be large in highly bursty situations, these errors appear to be much less than those which would be obtained by treating bursty traffic as if it were Poisson.     

Comparison of FEC types with regard to the efficiency of TCP connections over AWGN satellite channels

Optimizing the end-to-end throughput of a TCP connection (goodput) over geostationary satellite links is a challenging research topic. This is because the high delay-bandwidth product, together with a non-negligible random loss of packets, is a condition that considerably differs from the environments TCP was originally designed for. As a result, TCP performance is significantly impaired by the channel bit error rate. The literature is full of suggestions for improving TCP goodput, most based on modifications of the protocol itself. We only investigated the application of different FEC (forward error correction) types for TCP goodput optimization, leaving the end-to-end protocol unaltered. Using a method midway between analysis and simulation to evaluate the goodput of TCP long-lived connections, we first studied the influence of packet loss rate, introduced by errors on the channel, on the TCP goodput. We showed that, in some cases, the packet loss rate does not need to be negligible with respect to that caused by congestion, as it is widely-held opinion. We then applied physical-level FEC techniques, such as convolutional encoding/Viterbi decoding, Reed Solomon, link-level erasure codes and their combinations, over a wide field of signal to noise conditions of the satellite channel. For each FEC type, we found the FEC rate that maximizes the TCP goodput, in each channel condition. We finally compared the results of all FECs used between them, and presented the case of multiple TCP connections sharing the same link as well     

Impact of bursty error rates on the performance of wireless local area network (WLAN)

With an increasing popularity of DCF based wireless LAN, the modeling of 802.11 distributed coordination function (DCF) has attracted lots of research attention. Existing analysis of 802.11 DCF has been focused on the determination of the throughput and the packet delay under saturated traffic and ideal channel conditions. Although some recent papers address the saturated performance under a simple uniform error model, they can hardly capture the impact of bursty characteristics of wireless fading on the performance of 802.11 DCF. This paper presents exact formulae for the throughput and the delay in DCF for various traffic conditions when either saturated or unsaturated traffic load is present. A two-state Markov channel model is incorporated to present the bursty characteristics of channel errors. With our analysis, the impact of bursty channel error on unsuccessful transmission probability and the DCF performance can be determined. The results of our analytical framework reveal that the four-way handshaking scheme does not improve throughput substantially for light traffic load. However, for heavy traffic load, the four-way handshaking scheme is advantageous as compared to the basic access scheme. Also, extensive simulation is done to substantiate the accuracy of our analytical model.     

承载移动互联网的传输网络组网模式分析

为更好满足移动互联网业务传输承载和网络架构变化,通过分析移动互联网业务特点和发展趋势,比较承载移动通信系统的典型传输技术,提出了承载移动互联网的3种传输组网模式：SDH/MSTP/OTN＋PTN混合组网模式、SDH/MSTP/OTN：PTN独立组网模式和DWDM/OTN/ASON＋PTN联合组网模式,并对其系统组成和网络结构分析与讨论,得出在不同条件下应选择最适合承载移动互联网的传输组网。