SDH虚级联技术的实现与仿真

文章首先简要介绍了同步数字系列(SDH)虚级联的基本概念,然后重点分析了SDH虚级联的实现过程,最后利用VHDL语言对该过程进行了仿真.     

MSTP城域传送网新技术及发展

随着多业务传送平台(MSTP)城域传送网建设的快速发展,涌现了许多新技术,同时也存在许多亟待解决的问题.在具体建设过程中,也积累了许多值得注意的经验和思路.最后本文对城域传送网的建设和发展进行展望.     

低阶链路容量调整方案实现研究

讨论了数据流和LCAS控制同步实现及客户信号的映射等问题,分析了宿端回送成员状态的产生及传送方式和控制包CRC域的处理过程。     

Ethernet-over-SONET(EoS) over WDM in Optical Wide-Area Networks (WANs): Benefits and Challenges

Ethernet has been playing an increasingly important role in wide area networks (WANs), from both a service perspective and a transport-technology perspective. Unlike its dominant presence in local area networks (LANs), Ethernet in WANs has been increasing its popularity in three different directions, i.e., Ethernet-based layer-2 virtual private network (L2VPN) over layer-3 network, Ethernet over SONET (EoS), and Ethernet directly over WDM channels or optical fibers. In this paper, we investigate the benefits and challenges of using next-generation SONET/SDH techniques—namely SONET/SDH virtual concatenation (VCAT) and link-capacity adjustment scheme (LCAS)—to support Ethernet-based data services in intelligent optical WDM wide area networks. In particular, we evaluate the network performance improvement after employing VCAT. In order to fully utilize VCATs inverse-multiplexing capability, several simple and effective heuristic algorithms are proposed and evaluated.*Part of the work was accomplished while Keyao Zhu was a Ph.D. student in the Networks Research Lab. at University of California, Davis, under the supervision of Professor Biswanath Mukherjee. Summarized versions of this paper were presented at the IEEE/OSA Optical Fiber Communication Conferences OFC03 and OFC04 in Atlanta, GA, in March 2003 and in Los Angeles, CA, in March 2004, respectively.Corresponding author     

35kV系统双母线TV二次电压非正常并列事故原因分析及防范措施

针对35 kV系统双母线电压互感器二次电压切换不成功造成插件烧毁的故障,结合电压切换原理,分析了事故原因是由于刀闸辅助接点不通,使双位置继电器不能可靠复归,造成两TV二次电压非正常并列,引发事故.提出应尽量避免双母线分列运行,加强对刀闸辅助接点的维护以及考虑采用单位置继电器等防范措施.     

开关变压器技术在水轮发电机自同期并列上的应用

在发电机的并列方面有准同期并列与自同期并列两种方式,各有优缺点,从方便使用、实现自动化方面来看,自同期并列的优点要多些,但并列过程中仍存在一定的冲击电流。本文提出了一种基于开关变压器技术在水轮发电机自同期并列上的控制方案。该方案可有效减小自同期并列过程中的冲击电流,降低并列风险提升电网稳定性,电网长期高效稳定的运行。     

级联编码在地空数据链信道编码中的应用研究

为了克服传统信道编码方式的缺点,提高地空数据链信道传输的可靠性和传输效率,同时降低信道编码的复杂度,采用了级联编码的方法,将重复累加码与喷泉码进行级联后,应用到地空通信数据链信道编码当中。首先阐述了重复累加码、喷泉码的基本原理和编解码方法,重点介绍了两种码的级联方法,并通过实验进行了论证和比较,实验证明,通过级联方式编码后,数据链信道的误帧率明显降低,通信效果得到明显改善。研究结果表明,级联编码方法不仅能充分发挥喷泉码的特点,而且无线数据传输的可靠性得到明显改善。     

Analysis of Serial and Hybrid Concatenated Space-Time Codes Applying Iterative Decoding

In this letter, we investigate serial and hybrid concatenated space-time (SC-ST and HC-ST) codes applying iterative decoding topologies. The coding operations are based on the concatenation of convolutional coding, interleaving, and space-time coding along with a multiple-transmitter/multiple-receiver diversity system. Through the analysis of the SC-ST and HC-ST coding systems, improved design specifications can be selected for the component encoders with considerations of the wireless channel characteristics. Based on the iterative decoding process and the optimum parameter selection operations, a considerable improvement in the error rate performance is obtained. For the applied specs, the results indicate that at the frame error rate (FER) 10⁻² level the SC-ST coding system provides a coding gain of approximately 3 dB in comparison to the Tarokh, Seshadri, Calderbank (TSC) space-time (ST) code [1], where the HC-ST coding system provides an additional coding gain of approximately 1 dB beyond the SC-ST code.     

Multi-tiered service survivability in next-generation SONET/SDH networks

Rapid advances in next-generation SONET/ SDH and optical switching technologies along with dynamic generalized multi-protocol label switching control architectures have enabled many new service provisioning paradigms. In particular, a key addition is the new virtual concatenation feature that allows for inverse multiplexing of connection demands across SONET/SDH domains. This paper presents a novel tiered survivability scheme that leverages this feature to support multiple levels of service survivability and higher load carrying capability and service resiliency. Detailed simulation performance analysis results are also presented along with conclusions and directions for future work.