Robust data compression applied to rotary head DDS-3 tapes

A piecewise, lossless data compression scheme which limits the propagation of errors is used to compress text data. The error control coding of DDS is then applied to the compressed test data using a computer simulation. Burst channel errors representing longitudinal tape defects are simulated. It is shown that when data containing uncorrected errors is decompressed, the proposed strategy curtails error propagation with only a small drop-off in compression ratio     

Protection contre les erreurs en enregistrement magnétique numérique de télévision

In this paper the authors present the main problem of operating video tape recorders for television production, viz. picture degradations through multiple generations, which could be cancelled by using digital machines. Efficient error protection is mandatory. Burst error statistics are given as collected on a laboratory digital recorder as well as a physical interpretation. Different protection methods are used for luminance and colour differences, which results in sharing the available redundancy between two distinct coding systems. Adequate codes are selected through the use of two bounds stated as theorems. The main parameters of a possible system are presented. They are likely to be improved when further information is available to make an operating system practical.     

VS-OBR：一种无冲突虚同步光突发环网

 提出了一种利用光突发交换(OBS)技术组建WDM多波长光环网的新颖方案,称为“虚同步光突发环”——VS-OBR,该方案将数据信道划分为定长的数据突发时隙(DBS),并通过一种弹性偏置时间控制机制(ROTC)保持DBS与控制波长信道中的突发控制标签(BCL)的关联关系,实现数据信道上无冲突和丢失的媒质接入控制(MAC)。对该方案中偏置时间调整代价、最大饱和吞吐率和时延等性能进行的理论分析和仿真研究表明VS-OBR不仅可行而且带宽利用率高。     

TDMA卫星通信系统突发同步的性能研究

突发载波捕获和同步是TDMA系统的关键技术,使用数据序列辅助判决可有效缩短该处理过程需要的时间;在低接收信噪比下使用CAZAC序列的相关处理能够获得较高的突发捕获性能;比较了CAZAC序列和"1010"序列的载波和时钟同步误差估计性能,分析了它们在低信噪比门限时对信号快速捕获能力的影响。提出了2种序列组合应用实现载波快速同步的方案,完成信号捕获和载波估计功能。     

一种支持QoS的OBS网络数据信道调度协议

综合考虑了突发包所经历跳数和突发包的长度等因素,文章给出了一种新型的支持服务质量(QoS)的光突发交换(OBS)数据信道调度协议--考虑跳数的改进型JET模式下的优先级抢占(H-PPJET)协议.文章在OBS网络环境中对H-PPJET协议进行了仿真,并与JET模式下的优先级抢占(PPJET)协议进行了对比,仿真结果表明,H-PPJET协议改善了网络的吞吐量和丢包率性能.     

Automatic On-Line Correction of Differential Phase in NTSC Signals

This paper describes the design, development and testing of a new type of coder/ decoder called 'The Double Burst Codec' for colour television signals. This has the simplicity of the NTSC system and the differential phase correcting property of the PAL system. It is realized by modifying the horizontal blanking interval of the video signal to incorporate two subcarrier bursts, one at the blanking level and the other at the maximum luminance level. The first burst is used to regenerate the subcarrier in the decoder while the second is used for phase comparison with the regenerated subcarrier. Any phase error between the two is available as a d.c voltage for correction purposes. The error voltage and the luminance level together are fed to a level dependent phase shifting network for automatic on-line correction of the differential phase in the chrominance signal.     

流星余迹通信网络建模与仿真

流星余迹通信具有间歇性、信道时变性的特点,大大限制了其网络稳定性和数据传输量,因此,如何提高流星余迹通信的稳定性和数据传输量,是流星余迹通信的关键技术之一。在多基站环状网络结构的基础上,将各基站用高速有线链路连成全连通网络以克服环状网络稳定性低的缺点,并且对基于停等协议传输的流星余迹通信网络,利用Opnet网络仿真工具搭建了网络仿真模型,对包长度和发包速率进行了分析,最后给出了仿真结果。     

时隙光突发交换网络阻塞性能分析模型

文章介绍了基于时隙的光突发交换网络的结构及其特点，提出了相应的时隙化多波长多光纤系统阻塞分析模型，仿真结果表明该模型准确地反映了光纤数和帧长等网络参数变化对网络阻塞特性的影响．对于评估时隙突发交换网络性能和设计实现参数具有重要意义。     

光突发交换网络中突发组装办案研究

光突发交换（Optcal Burst Switching.OBS）被认为是在下一代光网络中起到至关重要作用的一种交换技术。边缘节点处突发包的组装作为业务接入OBS网络的第一步,是OBS研究的关键课题之一。 该文重点阐述了几种常用的突发组装方案：基于突发长度组装方案、基于组装时间组装方案、混合组装方案及自适应组装方案,并分析了它们的性能和优缺点。最后指出综合考虑网络业务流量、边缘节点的处理速度和信道带宽等因素的更加有效的突发组装算法是重点研究的内容。     

基于高阶累积量的突发信号检测技术

突发信号检测是非合作通信中的一项重要工作,是后续处理的前提。针对由高阶累积量作为判决统计量的信号检测方法,分析了高阶累积量法在实际信号检测中存在的问题,提出了相应的改进算法,该算法只用2个符号进行累积量估计,通过在高阶累积量的基础上增加滑动窗,对累积量值进行平滑处理,并通过窗内累积量值的变化自适应调整窗长,减小或消除了因数据过短引起高阶累积量估计值的抖动。仿真结果表明该算法可以提高信号检测性能。     

面向业务的光波长可调谐OBS环网

本文结合声光可调谐滤波器(AOTF)和光突发交换(OBS)技术构建了基于固定发射调谐接收机制(FTTR)的面向业务的光波长可调谐环型传送网.并对采用令牌轮询协议(RR/TOKEN)的光波长可调谐OBS环网在性能方面进行了计算机仿真研究,深入分析了最大突发包长度以及传输距离等参数对它的影响.     

OBS网络中基于拥塞避免的提前偏射路由研究

突发竞争是OBS(光突发交换)网络需要解决的关键问题,偏射路由作为一种有效的竞争解决方案而被广泛研究。文章提出了一种基于拥塞避免的提前偏射路由算法,利用周期性反馈的网络拥塞信息按一定概率提前偏射部分突发包。与传统的最短偏射路由算法相比,本算法达到了避免拥塞以及均衡网络负载的目的。仿真结果表明:文章所提算法在突发丢失率、吞吐量以及平均链路利用率方面性能都有所提高。     

业务自相似性对光突发交换调度算法影响分析

使用泊松业务流模型对光突发交换网络进行性能分析不能准确地反映网络状态。该文从理论上对突发包长度进行了推导,对基于时间门限汇聚机制下突发包数据流自相似程度进行了计算机仿真测量,并利用自相似业务流模型对光突发交换网络中比较常用的LAUC和LAUC-VF调度算法进行了性能仿真。仿真结果表明:基于时间门限的汇聚机制能够有效地降低数据流自相似程度,数据流的自相似特性对LAUC算法的影响并不非常明显,但对LAUC-VF算法的性能则产生了比较严重的影响,其突发包丢失率较泊松流平均增加了近3个百分点。     

Burst switching-an update

Burst switching research in dispersed control and integrated switching is described. Burst transport is integrated in that voice and data are switched through the same switching fabric and transmission media. Burst switching is compared to and distinguished from fast packet, fast circuit, and ATM (asynchronous transfer mode) switching. Misunderstandings about burst transport that have appeared in the literature are corrected, to wit: burst does not immediately clip in case of channel contention; burst switches voice and data in the same way; and a burst switch interfaces naturally to other types of switches. Round-trip delay performance is calculated to be less than 5 ms. The current status of the burst project is described     

WDM光突发交换网中的生存性问题

光突发交换拥有光电路交换和光分组交换两种方式的主要特征,是未来光网络的一种有希望的实现形式,本文对wDM光突发交换网络的实现做了简要的介绍,主要从wDM光突发交换网络的生存性出发对相关问题进行了分析研究,并提出了相应的解决方案.     

On the traffic modeling of burst aggregation algorithms using video and data traces

We obtain analytically the delay per packet in a burst for the three burst aggregation algorithms: Time based, Burst Length based and mixed Time and Burst Length based, assuming real video and aggregated Internet traces, as well as the IPP arrivals. For video traces we also obtain the probability that a playback machine will pause due to lack of frames when streaming video. Accuracy of the analytic results was established by comparing them to simulation data.     

流星余迹通信技术特征及影响

流星余迹通信利用流星电离余迹进行通信,它是一种突发的通信方式。流星余迹通信方式特殊,它具有很好的隐蔽性、很强的抗干扰能力,使其成为一种受到物理或电子攻击时的有效通信保障手段。这里给出描述流星余迹信道参数（流星达到率、可用时间比、平均持续期等）的数学表达及实测结果。制订2种流星突发通信的握手协议,并基于该协议和信道实测结果,估算得到流星突发通信的通过量和突发等待时间。     

一种 OBS 网络绝对区分服务实现机制

该文提出了一种用于OBS网络的绝对区分服务实现机制PSPJET.该机制结合使用额外偏移时间和Burst抢占/Burst主动分段丢弃技术,既能确保保证业务的数据丢失率不高于要求的最大丢失率,还能有效降低非保证业务的数据丢失率,提高网络性能.和现有的APJET机制相比,PSPJET机制对高业务强度的承受能力更好,还具有无需使用光缓存的优点.     

Time compression multiplex transmission system using a 1.3 μmsemiconductor laser as a transmitter and a receiver

A bidirectional system using 1.3 μm lasers as a transmitter and a receiver are investigated. The lasers considered are commercially available Fabry-Perot and distributed-feedback lasers. It is found that the poor performance of a laser receiver, compared to a PIN receiver, stems from three factors: low responsivity, high capacitance, and polarization dependence of responsivity, high capacitance, and polarization dependence of responsivity. The effect of each factor is evaluated. It has been clarified that the polarization dependence of sensitivity originates from the TE and TM modes dependence of both mode confinement factor and reflection at a facet. Using the measured parameters, 1.3-μm laser receiver sensitivity for a 10^-9 error rate is estimated. Burst data transmission experiments show that estimated sensitivities agree well with the measured values. Optical ping-pong transmission distance of narrowband services is determined based on estimated sensitivity     

OBS网络中冲突解决方法研究

在OBS网络中,当两个或多个突发包要求在同一时刻,同一输出端口的同一波长上预留资源时．就会产生突发数据包的资源竞争。如何解决资源竞争问题是OBS技术能否最终走向实际应用的关键技术之一。文章首先介绍OBS的基本原理、网络结构、OBS网络的资源预约机制、边缘路由器的封装机制和资源调度机制,接着研究解决OBS网络中突发数据包之间争夺链路资源问题的竞争解决机制,随后详细的给出四种竞争解决方案：光缓存、波长转换、偏射路由和突发分段丢弃,并分析了它们的性能。在此基础上,文章最后提出了各种资源竞争解决方案相结合的联合解决机制的思想。