SDH的比特率,帧结构,复用结构

随着光纤通信同步数字系列(SDH)的开发和应用,CCITT不断完善和补充SDH的规范。建议G.707、G.708、G.709规范了SDH的比特率、网络接点接口、帧结构、复用原理、映射格式和复用结构。本文摘编其主要内容,并与建议G.702、G.704规范的准同步数字系列(PDH)的比特率,帧结构进行比较,以说明SDH的优点、供技术人员参考,以利于合理规划和建设传输网络。     

前向纠错(FEC)在现代通信系统中的运用

本文首先叙述了前向纠错（FEC）的概念和发展由来，然后重点介绍了FEC在现代通信系统中的运用。     

SDH的帧结构与现代通信

本文主要以SDH传输系统优点作为出发点,并针对现代通信技术所需要克服的技术问题提出了SDH传输系统在现代通信中的应用研究情况,以期为提高SDH传输系统在现代通信中的应用提供一些参考和意见.     

光纤通信系统中的前向纠错技术

本文介绍了前向纠错技术(FEC)在高速光纤通信系统中应用的必要性,以及FEC采用的BCH-3码和RS-8码的编码技术,带内FEC、带外FEC和并行FEC三种实现方式及特点。最后阐述了FEC技术对光纤通信系统性能的改善。     

前向纠错技术及其在现代通信系统中的应用

对在数字通信系统中广泛使用的前向纠错（FEC）技术进行了较为详细的介绍,重点描述了不同的编码方法,分析了各种信道编码技术及其对系统性能的影响。     

前向纠错技术在数据广播中的应用

本文介绍了在数据广播中丢帧发生的一般原因，提出使用纠错码对发送内容进行保护，并在上基础上分析了一定丢帧概率下，使用前向纠错和不使用时的性能差异，尤其是大文件的一遍收齐概率的差异。从比较中，我们得到的结论是，使用前向纠错码可以大大地提高文件的一遍收齐概率，从而减少用户的平均等待时间。     

高速率DWDM海底光纤通信系统中的前向纠错编码技术

介绍了高速率DWDM海底光纤通信系统中所使用的前向纠错编码技术,对不同的超强纠错编码技术进行了分析和比较。有试验数据表明,超强纠错编码技术比ITU-T建议G.975和G.709中定义的前向纠错编码——RS(255,239)码的纠错能力更强。     

OTN的前向纠错技术

介绍了应用于光传送网中的前向纠错技术的发展。从第一代ITU—T的标准FEC、第二代增强型FEC,到PMC—Sierra公司最新研发的、针对40／100Gbit／s光传送网应用的第三代SwizzleFEC,并讨论了第三代FEC的技术创新和性能比较。     

前向纠错技术在EPON中的应用研究

在EPON中引入前向纠错(FEC)技术,能有效地增加PON的光分路数和增大信号的传输距离。对于在EPON中加入FEC功能所涉及到的FEC线路综合编码、帧结构的设计以及兼容性等问题进行了分析,并进一步给出了相应的解决方案。     

光传输网络性能与前向纠错

为了提高光传输网络性能,人们将前向纠错技术应用于高速光纤通信系统中。文章对同步数字系列/密集波分复用(SDH/DWDM)传输网络性能进行了简要分析,讨论了前向纠错技术以及它对系统误码率的改善。     

FEC Performance Analysis Based on Poisson and Bursty Error Patterns for SDH and OTN Systems

This paper analyses and compares the performance of International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) recommended forward error correction (FEC) for the Synchronous digital hierarchy (SDH) system and the newly ratified Optical transport network (OTN) system. The analysis and comparison are based on simulation results using Poisson and bursty error patterns. While a Poisson error pattern is a commonly studied environment for these systems, a bursty error pattern is not. The simulation results show that the FEC for both SDH and OTN support Poisson errors well. However, for bursty errors, it is found that the FEC for SDH does not work well, while the FEC for OTN is working well for short burst length only.     

高速SDH帧同步系统性能与同步码组选择

介绍了高速 SDH系统中的帧同步器的设计 ,分析了影响帧同步器性能的参数选择。在分析的基础上 ,以 STM- 4为例选择帧同步器参数和帧同步码组 ,实现了一种应用于高速SDH系统的并行帧同步器的设计。     

SDH系统帧同步的研究与ASIC实现

介绍了SDH系统中的帧同步器的设计思想,依据ITU-T关于SDH技术体制的建议,分析并计算了STM-1帧同步器的几个重要参数,选择了合适的帧同步码组.并在此基础上,采用ASIC设计方法设计实现了用于SDH系统的STM-1的并行帧同步器,并进行了仿真模拟.     

Estimation of accurate effective loss rate for FEC video transmission

We propose an algorithm for adjusting data transmission parameters, such as the packet size and the code rate of forward error correction (FEC), to obtain maximum video quality under dynamic channel conditions. When determining transmission parameters, it is essential to calculate an accurate effective loss rate that reflects FEC recovery failures and over-deadline packets. To this end, we analyze the delays caused by FEC coding and the potential packet size variations. In our analysis, we consider the effect of delayed transmission of video packets incurred by the parity packets as well as the encoder and decoder buffers. With the analysis reflecting the delay effect, we are able to accurately estimate the delay patterns of all video packets. Based on the analysis results, we establish an accurate model for estimating the effective loss rate. Simulations show that the proposed effective loss rate model accurately estimates the effective loss rate and significantly improves the reconstructed video quality at the receiver.     

一种新的SDH开销处理方法

文章提出了一种较为实用的SDH系统方案，并在系统中采用了一种新型的、便于系统升级的开销处理方法，该系统已通过了电路实现和硬件的测试，     

Improved FEC Code Based on Concatenated Code for Optical Transmission Systems

The improved three novel schemes of the super forward error correction(super-FEC) concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon(RS)+Bose-Chaudhuri-Hocguenghem(BCH) inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS(255,239)+RS(255,239) code and the RS(255,239)+RS(255,223) code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS(255,239) code and other codes, and their signal to noise ratio gains are respectively 2～3dB more than that of the RS(255,239)code at the bit error rate of 1×10 -13 . Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.     

高速SDH复接器帧同步系统的设计和性能分析

本文介绍了一种应用于SDH系统中的容错帧同步器的设计,分析表明此方法在满足ITUT建议的前提下,提高了帧同步器的性能。本文在分析的基础上,选择参数,实现了一种应用用于高速SDH系统的并行帧同行器的设计。     

Near-Optimum Iterative Multiuser Receiver for FEC Encoded DS-CDMA

The powerful iterative algorithm of Turbo code is employed in the proposed iterative multiuser receiver for the downlink of a forward error correction (FEC) coded direct-sequence code-division multiple access (DS-CDMA) environment. The receiver iterates between the 2 coding dimensions, namely the spreading codes and the FEC codes. The optimum iterative multiuser receiver uses the optimum decentralised single-user detector to generate the single-user extrinsic information for the single-user decoders. This paper suggests a near-optimum detector using a folded trellis preselection stage for the multiuser signal detection, in order to reduce the dominating complexity of the optimum decentralised detector. Simulation results show that performance is close to optimum. The effect of the single-user decoders' extrinsic information on the signal detection stage is also investigated and it is found that extrinsic information improves performance.     

视频信号在SDH上的传输技术

介绍了SDH的帧结构和基本复用原理，在此基础上，探讨了视频信号在SDH上的传输技术。文章详细叙述了2．048Mbps的电视会议信号、34．368Mbps的视频信号和8Mbps的MPEG－2传输流复用映射进SDH帧结构的方法；SDH数字复用设备的组成和原理；最后介绍一个具有SDH接口的MPEG－2多媒体系统终端机设计实例。