基于DSRC的车载自组网终端设计及性能测试

利用低功耗X86平台和嵌入式Linux平台,设计了一种基于DSRC的车载自组网通信系统方案。介绍了系统的软硬件架构,并进行了软硬件的设计与实现,最后在城市视距场景和跨江大桥场景下对该系统进行了丢包率、吞吐量以及延时抖动的测试分析。     

自组网路由协议综述

自组网路由协议用于监控网络拓扑结构变化,交换路由信息,定位目的节点位置,产生、维护和选择路由,并根据选择的路由转发数据。本文综述了自组网路由协议研究方面的一些最新工作,描述了设计自组网路由协议所面临的问题,并着重对该研究开展以来所提出的各种主要协议进行了对比、分析和分类阐述,为进一步的研究提出了新的课题。     

自组网的路由协议及其QoS保障

自组网是一种新型的移动计算机网络，它应用广泛，并具有重要的商业价值。首先介绍了自组网的概念和特点，然后分析了自组网路由协议的特点与设计思路，并丰此基础上讨论了在自组网环境下实现QoS的策略与方法。     

TDMA自组网的QoS设计

QoS设计是一个复杂的问题,IETF针对有线网络提出实现QoS的2种标准模型;然而在无线自组网中,由于隐终端、显终端问题的存在和带宽限制问题,有线网络使用的QoS模型略显繁琐并使实现无线QoS较为困难。通过对TDMA方式自组网的分析,使用跨层合并方法设计一个QoS路由协议,并得到集成服务模型在无线自组网络的一个实现。通过仿真,验证此路由协议设计的正确性,同时分析此协议性能,结果表明该路由协议高效可行。     

基于Ka/Ku相控阵天线的空基自组网协议设计

针对空基自组织网络的大容量通信需求,首先提出了基于频分复用的定向MAC协议,在邻居发现过程中将测距算法与多维尺度变换定位算法相结合得到每个节点的相对位置,并设计了双预约资源分配算法,完成定向数据传输;然后提出了定向路由协议,解决了次佳路由问题和路由应答风暴,并加入相邻搜索、链路质量评估和备用路由,降低了协议开销。空基自组网基于Ka/Ku相控阵天线的定向传播特性以及Ka/Ku频段频谱资源丰富的特点,使用频分复用、空分复用技术实现多个信道的高速并行传输,从而极大地提高网络的吞吐量。     

基于车载自组网的动态交通信息的挖掘和利用

动态交通信息系统是智能交通系统中重要的组成部分,作为一种新兴的车辆间无线通信网络技术,车载自组网可有效提高高速行驶车辆间的信息共享能力。文章阐述利用基于车载自组网的交通信息采集和交通事件协同检测算法、大规模海量交通信息的分布式组织和实日寸处理方法、基于位置的交通信息分发协议等技术,构建一个动态交通信息系统,实现改进交通信息系统中的事件检测的准确性和实时性,提高大规模交通信息处理的实时性,改善交通信息分发的针对性。     

移动自组网中的典型位置服务协议比较

到目前为止,移动自组网已经开发很多基于不同策略的路由协议,这些路由协议可分为基于网络拓扑的路由协议和基于位置信息的路由协议。本文主要介绍基于位置信息的路由协议及几种典型协议的分析比较。     

航空自组网的现状与发展

近年来,随着移动Ad Hoc网络研究与应用的不断深入,许多研究机构和学者正在将其应用于航空通信中,产生了崭新的研究领域——航空自组网。本文概述了航空自组网的基本概念、主要特点及应用场合,介绍了在这一领域比较活跃的研究机构以及其主要工作,分析了航空自组网的关键技术,并展望了未来的发展方向。     

无人机自组网研究进展综述

随着世界各国对无人机(UAV)运用的不断重视、多无人机协同应用的兴起和无线自组网应用研究的迅猛发展,无人机自组网已成为新的研究热点.首先对无人机自组网的基本概念、主要特点和应用优势进行了总结,进而重点对MAC协议、路由协议、传输协议、跨层设计、机会网络5个方面关键技术的研究进展进行了系统综述,简要介绍了国内外主要研究机构的实验平台开发情况,最后指出了无人机自组网存在的挑战和亟待研究解决的重点问题.     

车载自组网中的网络与信息安全

因自组织网络无中心的特点,传统有中心网络中成熟的安全保障机制无法得到直接应用。为了使车载通信技术得到更加广泛的应用,安全问题必须得到很好的解决。文章对车载自组网的安全需求及目标进行分析,然后从安全路由、密钥管理和入侵检测3个方面对车载自组网安全研究的现状进行介绍。在这3个方面中,安全路由研究最为广泛,而密钥管理则是保障车载自组网安全的关键。     

Vehicle density based multihop broadcast protocol in VANET

In vehicular ad hoc networks (VANET), the medium access control (MAC) protocol was of crucial importance to provide time-critical multihop broadcast. Contemporary multihop broadcast protocols in VANET usually choose the farthest node in broadcast range as the forwarder to reduce the number of forwarding hops. However, it was demonstrated that the farthest forwarder may experience long contention delay in case of high vehicle density. An IEEE 802.11p-based multihop broadcast protocol vehicle density based forwarding (VDF) was proposed, which adaptively chose the forwarder according to the vehicle density. The evaluation results in safety warning and online game applications show that, VDF could shorten broadcast delay by achieving the proper trade-off between the contention delay and coverage speed.     

Hybrid 802.11p-cellular architecture for NDN-based VANET

Vehicular network communications (VANET) face multiple challenges due to their intermittent connections and the rapid changes in their topologies. In recent years, several research efforts have explored the use of content-centric approaches to alleviate some of these challenges. One of these promising network designs is Named Data Networking (NDN), which has become a valid solution to support VANET applications. However, in the NDN architecture, the main forwarding mechanism for the interest packets is flooding. This forwarding mechanism will result in excessive collisions, which will lead to the broadcast storm problem. In this paper, we propose VC-NDN: a hybrid and hierarchical Named Data Networking architecture for VANETs. VC-NDN improves content retrieval efficiency through an adapted NDN-based communication model. VC-NDN includes a new interest forwarding scheme to reduce packet collision in the network and an efficient mechanism to support push-based traffic. Furthermore, to reduce communication costs, VC-NDN uses two communication technologies in parallel, namely, IEEE 802.11p and cellular communications, while keeping the usage of the cellular network at a minimum level. Finally, to reduce the impact on vehicle mobility, VC-NDN follows a hierarchical clustering architecture. Specifically, a density-based clustering algorithm is designed to create and maintain stable clusters with multihop communication capability. Our performance study shows that VC-NDN outperforms the basic VNDN solutions in terms of data retrieval delay and packet delivery ratio while minimizing the usage of the cellular network.     

基于协议序列平均分配算法的VANET信道接入机制

为了提高VANET中节点的吞吐量性能,提出基于协议序列平均分配算法的信道接入机制。在高速公路场景下,规划IEEE 802.11p业务信道与竞争区段的映射,并根据用户保障序列的特性设计帧结构。通过少量反馈确定竞争区段的节点数,并提出循环轮流分配法实现平均意义上非整数个序列的分配。仿真结果证明了理论分析的有效性,在实际路况中均分法与经典方法相比吞吐量性能明显改善,并且节点越稀疏、物理层数据传输速率越高,吞吐量性能提升越明显,同时可保持较低的网络开销和较好的信道接入公平性。     

FGWSO‐TAR: Fractional glowworm swarm optimization for traffic aware routing in urban VANET

In mobile distributed applications, such as traffic alert dissemination, dynamic route planning, file sharing, and so on, vehicular ad hoc network (VANET) has emerged as a feasible solution in recent years. However, the performance of the VANET depends on the routing protocol in accord with the delay and throughput requirements. Many of the routing protocols have been extensively studied in the literature. Although there are exemptions, they escalate research challenges in traffic aware routing (TAR) protocol of VANET. This paper introduces the fractional glowworm swarm optimization (FGWSO) for the TAR protocol of VANET in an urban scenario that can identify the optimal path for the vehicle with less traffic density and delay time. The proposed FGWSO searches the optimal routing path based on the fitness function formulated in this paper. Fractional glowworm swarm optimization is the combination of the GWSO and fractional theory. Moreover, exponential weighted moving average is utilized to predict the traffic density and the speed of the vehicle, which is utilized as the major constraints in the fitness function of the optimization algorithm to find the optimal traffic aware path. Simulation of FGWSO shows the significant improvement with a minimal end‐to‐end delay of 6.6395 seconds and distance of 17.3962 m, respectively, in comparison with the other existing routing approaches. The simulation also validates the optimality of the proposed TAR protocol.     

VANET路由协议设计时的网络容量仿真分析

针对车载自组网中节点移动速度快、拓扑变化频繁以及无线信道质量不稳定的特点,提出了此类网络的路由协议必须综合考虑业务需求、网络能力以及自组网本身的特点等因素的设计思想。分析了承载业务分为低速率的导频信道和高速率的业务信道对传输速率的不同要求,研究了在选择路由协议时的网络容量上、下限问题。仿真实验结果表明,节点的可行吞吐量的上下限将随着无线电波衰减系数和节点带宽的增大而增大。在车载自组网路由协议设计时需要考虑这种关系,从而提高节点的可行吞吐量。     

基于802.11p/WAVE的车联网连通性模型及其应用研究

首先对高速公路交通场景的车联网连通性模型进行了研究,分析推导了某特定路段上任意两车之间的连通概率、连通集直径长度以及连通集数目等连通性模型参数指标与车辆密度及传输距离之间关系的数学解析式,并在此基础上分析出车联网的节点位置是满足伽马分布的结论。接着根据车联网报文存储转发的特点,设计了一种车联网的报文格式,并应用连通性模型中的相关参数解析式给出了广播消息报文的TTL字段的初始值设定方案,从而能够有效地控制广播报文的泛滥情形,仿真实验证实了所建模工作的有效性,为车联网WAVE协议栈上层协议的设计提供了重要的理论基础。     

Mixing greedy and predictive approaches to improve geographic routing for VANET

In recent years, thanks to the development and popularization of wireless network technologies, the issue of vehicular ad hoc network (VANET) has received great attention, and more and more VANET‐related researches have been brought up. Generally speaking, the biggest difference between VANET and traditional ad hoc network is the velocity of carriers because in VANET, the velocity of vehicles, the carriers, is much higher than those in traditional ad hoc. Therefore, it would be a great challenge to forward data efficiently in VANETs and many researches proposed have focused on the development of routing protocols. The current proposed routing protocols are all assumed to simulate in a distributed and ideal environment. As for the complex geographic environments, such as urban scenarios, extra amendments must be needed to improve the efficiency of the routing protocols. Thus, the main purpose of this paper is to design a suitable routing protocol for urban scenarios with better performance and adaptability. For this reason, greedy on straight roads and predictive at the intersections (GSPI) routing protocol is proposed to use greedy mode on straight roads and to use predictive mode at the intersections. In greedy mode, we choose the next hop according to the weight value that combines the distances and multi‐rate. In predictive mode, we predict the directions of the vehicles to determine the next hop. The simulation results reveal that our proposed algorithm indeed proves its feasibility. Copyright © 2010 John Wiley & Sons, Ltd.     

无线传感器网络MAC协议的实现与分析

介绍了无线传感器网络中2种重要的基于竞争的MAC协议(IEEE802.11和S-MAC)原理。从平台的整体架构和运行环境2个方面对无线传感器网络测试平台的设计进行了详细介绍。对于IEEE802.11和S-MAC协议的实现,具体描述了通信接口的定义和组件重用技术,从状态机的角度阐述了协议的运行流程。根据测试数据从不同方面对IEEE802.11和S-MAC协议进行了对比分析。实验结果真实地反映了协议的性能,对无线传感器网络MAC协议的研究有着积极的推动作用。     

OFDM系统符号同步的FPGA设计与实现

分析了符号定时偏差对OFDM系统中数据传输的影响,参考IEEE802.11a标准给出了基于训练序列的符号同步算法在FPGA中的硬件实现方案,并在ISE平台中进行验证.仿真结果表明,该实现方案有效减少了硬件资源的使用,提高了运行效率,能够实现有效的符号同步,并且易于进行工程实现.     

IEEE 802.11n LDPC译码的设计与实现

提出了一种针对IEEE 802.11n准循环非规则LDPC译码器VLSI的设计方法.设计使用了交互信息存储器最小化设计策略,交互信息存储器与基矩阵有值点一一对应原则,最大程度减少了存储器的开销.校验节点处理采用了一种层次化偏置的最小项算法来降低复杂度,并选出合适的偏置量来提高译码器性能.采用SMIC 0.13μmCMOS工艺设计并实现了该译码器,在时钟频率为133.3MHz时,最大数据吞吐率为100Mb/s,功耗为73mW.