VANET中安全信息的快速可靠广播路由算法

为了满足VANET中交通安全信息实时可靠传输的需求,文中提出了一种基于自适应认证重传机制的多跳广播路由算法(ACR-BA).首先,为了节省网络资源,ACR-BA算法设计了两种短控制包,有效地抑制了传输冗余;其次,为了降低竞争信道的碰撞概率,基于地理位置划分了候选节点集,并结合控制包认证机制在一个候选节点集中仅确定出唯一的转发节点;然后,根据网络负载状况设计了一种基于单位基准时隙的自适应机制,设置尽量小的退避等待时间,提高信息广播的实时性;最后,设置了针对短控制包和数据包的超时重传保障机制,在保证算法实时性的基础上最大限度地提高可靠性.理论分析和仿真结果表明,与传统洪泛算法和时隙1坚持算法相比,ACR-BA算法有效地降低了网络中的冗余数据量,在实时性和可靠性两方面均有较大的性能提高.     

论基于TCP的数据流拥塞控制技术

本文在介绍TCP基本机制的基础上,就数据流在拥塞控制方面的发展进行了研究,对TCP拥塞控制的改进机制进行了讨论,探讨了网络拥塞出现的原因及TCP拥塞控制的基本策略,论述了TCP拥塞控制的改进方案,并提出了其进一步的研究方向.     

超宽带IP网络环境下的视频分组丢失修复技术研究

基于IP超宽带网络传送视频节目已经成为三网融合背景下的发展趋势。相对于传统广电运营商的同轴广播网,IP网络更加复杂,出现分组丢失的可能性更大,可能会影响用户的观赏体验。目前的视频编码技术本身的冗余机制大多适用于同轴网络,因此有必要对IP网络中的视频分组丢失修复机制进行研究。本文分析了分组丢失对视频质量的影响,并对目前主流的分组丢失修复技术进行了针对性分析和比较,结合测试结果,给出了可行的分组丢失修复技术应用建议。     

选择性重传法在IPTV中的应用

为提高视频通信质量,有多种差错控制方法,其中选择性重传,是一种解决分组丢失问题的有效方法。视频信号传输的选择性重传方法,即基于决策位置、基于优先级、基于网络状态和基于不同层面的选择重传算法,都可以提高视频传输质量。针对不同分类方法讨论现有的各种选择重传方案,实现差错控制的目的。     

A framework of prioritized burst segmentation supporting controlled retransmission in OBS networks

In optical burst switching (OBS) networks, burst contentions in OBS core nodes may cause data loss. To reduce data loss, retransmission scheme has been applied. However, uncontrolled retransmission may increase network load significantly and data loss probability defeating the retransmission purpose. In addition, in a priority traffic existing OBS network, OBS nodes may apply different retransmission mechanisms to priorities bursts for quality-of-service (QoS) support. This study has developed a controlled retransmission scheme for prioritized burst segmentation to support QoS in OBS networks. Unlike previous works in the literature, we have set a different value to retransmission probability at each contention and propose a retransmission analytical model for burst segmentation contention resolution scheme. In addition, we have applied the proposed retransmission scheme to the prioritized burst segmentation for QoS support. We have taken into account the load at each link due to both fresh and retransmitted traffic, and have calculated the path blocking probability and byte loss probability (ByLP) for high-priority and low-priority burst to evaluate network performance. An extensive simulation has been proposed to validate our analytical model.     

A QoS‐supported controlled burst retransmission scheme in OBS networks

Burst retransmission can reduce data loss in burst contention in optical burst switching (OBS) core nodes. However, uncontrolled burst retransmission may significantly increase the network load and data loss probability, defeating the purpose of retransmission. Therefore, controlled retransmission should be studied to achieve reasonable retransmission, particularly to support quality of service (QoS) in OBS networks in which priority traffic exists. In this paper, we develop a QoS‐supported controlled retransmission scheme in OBS networks. Different from previous works in the literature, we set a different value for the retransmission probability at each contention for both high‐ and low‐priority bursts, set different retransmission probabilities for bursts of different priorities for QoS support, and propose a retransmission analytical model for OBS networks. We take into account the load at each link due to both the fresh and the retransmitted traffic and calculate the path‐blocking probability and the burst loss probability for high‐priority and low‐priority bursts to evaluate the network performance. An extensive simulation is proposed to validate our analytical model. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

WCDMA空中接口RLC层的AM传输方式关键技术的研究

以WCDMA标准为依据，简要介绍了该标准空中接口方案的无线链路控制子层（RLC层）,并对RLC层确认数据传输方式中发送／接收缓冲区的设置以及状态报告的形成进行了深入探讨。     

Efficient wireless multicast retransmission using network coding

In wireless multicast,network coding has recently attracted attentions as a substantial improvement to packet retransmission schemes.However,the problem of finding the optimal network code which minimizes the retransmissions is hard to solve or approximate.This paper presents two schemes to reduce the number of retransmissions for reliable multicast efficiently.One is retransmission using network coding based on improved Vandermonde matrix(VRNC),the other is retransmission using network coding based on adaptive improved Vandermonde matrix(AVRNC).Using VRNC scheme the sender selects the packets all receivers have lost and encodes them with improved Vandermonde matrix;when receivers receive enough encoded retransmission packets,all the lost packets can be recovered.With AVRNC scheme,the sender can obtain the recovery information from all the receivers after sending out per retransmission packet,and then the improved Vandermonde matrix can be updated,thus reducing the complexity of encoding and decoding.Our proposed schemes can achieve the theoretical lower bound assuming retransmission packets lossless,and approach the theoretical lower bound considering retransmission packets loss.Simulation results show that the proposed algorithms can efficiently reduce the number of retransmissions,thus improving transmission efficiency.     

基于实测流量的网际分组丢失率分析

分组丢失率是评价网络性能的一个重要指标。提出了一种利用完整TCP流计算实测数据中分组丢失率的方法,并基于实测数据对CERNET江苏省网与外部不同网络分区的分组丢失率进行分析。算法给出了基于实测数据的分组丢失率包括首次分组丢失率pfl、整体分组丢失率psl和重传率prp 3个测度。统计分析表明,在绝大多数情况下,pfl比psl小,而prp比pfl和psl明显要高,验证了分组丢失对网络性能的影响以及重传率明显比分组丢失率高。     

实时数据分发可靠传输的研究

数据分发服务（DDS）是由对象管理组织（OMG）提出的一种适用于分布式实时系统的数据分发规范,它适应了新一代航空电子系统对机载通信平台的要求。本文研究TDDS的可靠传输机制,它通过添加消息序列号和丢失数据重传的方式提高了传输可靠性。这种实时的、可靠的通信方式对机载实时数据分发的研究具有重要的指导意义。