一种适用于稀疏无线网的定向Geocast路由协议

Geocast协议是一种向特定区域内所有节点传送数据的多播协议。由于传统Geocast协议不适应Geocast组内节点稀疏的环境,本文提出一种适用于稀疏无线网络的定向Geocast路由算法。算法根据节点所处位置,将控制包的洪泛分为两部分:受限洪泛将在距源节点较近的Geocast区内节点与源节点间建立路由;定向洪泛可在远离其它Geocast区内节点的Geocast节点与源节点间建立路由。实验结果表明,在节点稀疏的环境下,该算法比现有Geocast协议具有更好的性能。

无线多跳网络GeoGRID协议研究

Geocast是一种基于方向性投递的无线多播路由协议,能够减少冗余数据包,缩短多播时延。现有Geocast协议并不适用于稀疏网络环境,存在时延较大、数据冗余较高等缺陷。为了提高GeoGRID协议在稀疏网络中的性能,提出了GeoGRID-LBM和A-GeoGRID两种新型协议,利用网关节点掌握两跳网关节点邻居的信息,减少信道竞争和数据包碰撞概率,仿真实验表明,这两种改进型GeoGRID能够将数据端到端时延减少14%,降低冗余数据包数量达26%。

VANETs城市场景下基于自适应时延的Geocast路由协议

基于广播式的Geocast路由协议能够在特定的地理区域内高效地发布数据。然而,广播模式引起冗余重播,易导致广播风暴问题。另外,由于城市场景下建筑物的影响,现有的多数广播抑制方案难以应用于城市环境。为此,提出面向城市的基于自适应时延的Geocast路由协议UGAD。UGAD采用了基于自适应时延的广播抑制方案,降低发生广播风暴的概率。同时,考虑到交叉路口的地理优势,给位于交叉路口的车辆"优惠"时延,使其具有优先转发数据包权力,从而提高数据包到达率。此外,考虑到城市道路的复杂性,UAGD采用基于交叉路口转发IF和贪婪转发GF两个模式,依据不同的道路情况选择不同的转发模式,从而降低冗余重播,并保持高的数据包到达率。最后,针对城市场景进行仿真,结果表明提出的UGAD具有高的数据包到达率,低的数据包重播率。

Real traffic-data based evaluation of vehicular traffic environment and state- of-the-art with future issues in location-centric data dissemination for VANETs

Extensive investigation has been performed in location-centric or geocast routing protocols for reliable and efficient dissemination of information in Vehicular Adhoc Networks （VANETs）. Various location-centric routing protocols have been suggested in literature for road safety ITS applications considering urban and highway traffic environment. This paper characterizes vehicular environments based on real traffic data and investigates the evolution of location-centric data dissemination. The current study is carded out with three main objectives： （i） to analyze the impact of dynamic traffic environment on the design of data dissemination techniques, （ii） to characterize location-centric data dissemination in terms of functional and qualitative behavior of protocols, properties, and strengths and weaknesses, and （iii） to find some future research directions in information dissemination based on location. Vehicular traffic environments have been classified into three categories based on physical characteristics such as speed, inter-vehicular distance, neighborhood stability, traffic volume, etc. Real traffic data is considered to analyze on-road traffic environments based on the measurement of physical parameters and weather conditions. Design issues are identified in incorporating physical parameters and weather conditions into data dissemination. Functional and qualitative characteristics of location-centric techniques are explored considering urban and highway environments. Comparative analysis of location-centric techniques is carded out for both urban and highway environments individually based on some unique and common characteristics of the environments. Finally, some future research directions are identified in the area based on the detailed investigation of traffic environments and location-centric data dissemination techniques.

An Energy-Efficient Clique-Based Geocast Algorithm for Dense Sensor Networks

This paper proposes an energy-efficient geocast algorithm for wireless sensor networks with guaranteed de-livery of packets from the sink to all nodes located in several geocast regions. Our approach is different from those existing in the literature. We first propose a hybrid clustering scheme: in the first phase we partition the network in cliques using an existing energy-efficient clustering protocol. Next the set of clusterheads of cliques are in their turn partitioned using an energy-efficient hierarchical clustering. Our approach to con-sume less energy falls into the category of energy-efficient clustering algorithm in which the clusterhead is located in the central area of the cluster. Since each cluster is a clique, each sensor is at one hop to the cluster head. This contributes to use less energy for transmission to and from the clusterhead, comparatively to multi hop clustering. Moreover we use the strategy of asleep-awake to minimize energy consumption during extra clique broadcasts.

Intermittent Geocast Routing in Urban Vehicular Delay Tolerant Networks

Nowadays, both vehicular active safety service and user infotainment service have become two core applications for urban Vehicular Delay Tolerant Networks（u VDTNs）. Both core applications require a high data transmission capacity over u VDTNs. In addition, the connection between any two vehicles in u VDTNs is intermittent and opportunistic. Intermittent data dissemination over u VDTNs is a stringent and challenging issue. In this paper,we propose Intermittent Geocast Routing（IGR）. For the first step, IGR has to estimate the active connection time interval via the moving directions and velocities between any two vehicles. Second, the throughput function for u VDTNs is fitted by building a wavelet neural network traffic model. Third, the throughput function within the effective connection time interval is integrated to obtain the forwarding capability estimation of the node. Fourth, a high-efficiency geocast routing algorithm using the node forwarding capability for u VDTNs is designed. Finally, IGR is simulated on the opportunistic Network Environment simulator. Experimental results show that IGR can greatly improve the packet delivery ratio, transmission delay, delay jitter, and packet loss rate compared with the state of the art.