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1.
Vehicular Ad Hoc Networks (VANETs) can provide value-added services to both drivers and passengers with on-board vehicular communication systems. Node mobility and volatile wireless connection in VANETs affect inter-contact time ( T I ) between mobile nodes, which greatly degrades the performance of vehicular applications. Nevertheless, the node spatial distribution in VANETs is another important factor especially in real applications. It positively affects the inter-contact time of vehicular nodes. By leveraging it, we can significantly improve the performance of data transmissions and inter-vehicle communication. To this end, we investigate the data collected from around 4,000 taxisin Shanghai and propose in this paper an efficient hot road mobility model. We find that most taxis distribute on some hot roads, which makes the node spatial distribution follow the power law. Based on this observation, we propose the concepts of indirect contact and heterogeneous inter-contact time ( T H ) to reveal how hot roads can change the distribution of inter-contact time. We find that the tail distribution of T H also appears the power law, and both node spatial distribution and T H distribution decay at least as the power law. We further propose a model for detecting vehicle mobility in hot roads, which can generates synthetic traces that captures both spatial and temporal features of nodes in VANETs. 相似文献
3.
The paper proposes a mobility handover scheme MHVA for IPv6-based vehicular ad hoc networks. In MHVA, a vehicle is uniquely identified by its home IPv6 address, and it can keep the communication with other nodes without a care-of address during the mobility process. In addition, MHVA adopts an advanced mobility handover mechanism where the mobility handover operation in the network layer is completed before the one in the link layer is performed. As a result, during the advanced mobility handover process, a vehicle can keep the connection with its current associated AP in the link layer, so it can receive the data forwarded by the AP. Therefore, the packet loss rate is reduced, the mobility handover cost is decreased, and the mobility handover delay is shortened. From both the theoretical perspective and simulative perspective, the performance parameters of MHVA are evaluated, and the data results show that the mobility handover cost of MHVA is lower and the mobility handover delay is shorter. 相似文献
4.
考虑到城市环境中障碍物对网络性能的重要影响,在NS2(Network Simulator version 2)中加入了代表障碍物的概率穿透模型,使仿真环境更接近真实环境。针对AODV(Ad hoc On-Demand Distance Vector Routing)协议应用在城市场景下的缺陷,提出了一种改进的AODV协议——GE-AODV(Geocast Enhanced AODV)协议,该协议是基于位置信息的协议,并采用了多播方式来转发控制信息。仿真表明,GE-AODV降低了网络时延和控制开销,提高了网络可靠性。 相似文献
5.
Vehicular Ad Hoc Networks (VANET) are the foundation of Intelligent Traffic System (ITS), and recently many MAC protocols for VANET are proposed, among which a reliable MAC protocol called ADHOC has aroused much attention. By investigating the details of ADHOC protocol, we have discovered several unsolved problems that might lead to network failure. In this paper, we provide a quantitative analysis of the success probability for contending nodes and prove that an adaptive frame length is quite necessary. We propose Adaptive-ADHOC (A-ADHOC) MAC protocol, which implements a robust mechanism supporting the adaptive frame length. Evaluation result shows that A-ADHOC can maintain a high contending success probability and obtain about 50% reduction of response time over original ADHOC protocol, while providing important enhancement on network scalability and robustness. 相似文献
6.
VANETs- Vehicular Ad Hoc Networks depends on organizing the innovation where the vehicles go about as versatile hubs for shaping a correspondence arrange. The arrangement of vehicular specially appointed systems doesn't just encourage novel telematics applications. The selection of dynamic wellbeing application raises new dangers to street wellbeing if security issues are not appropriately taken care-of. An extraordinary dynamic security application is viewed as the empowers those foresights the passing of the trading of nearby threat alerts that depends on singular perceptions. VANET is considered by many specialist co-ops in urban situations. As it were, communicate tempest corrupts the directing presentation. The issue is addressed and examined by various protocols such as AODV, DSR, DYMO, TORA and TIHOO. The proposed protocol Advanced and enhanced security protocol for VANET (AESP-VANET) which is an upgraded that also depends on improved fluffy and cuckoo ways for dealing with location of the steadiest way between a source and a goal hub. The disclosure of the courses is restricted brilliantly by AESP-VANET by utilizing fuzzy framework thereby constraining the messages that are course demand. The improved cuckoo calculation in hybrid methodology, which is one of the best meta-calculations particularly in the huge inquiry space, brilliantly chooses the most steady and ideal course among realized courses by computing an upgraded wellness work. AESP-VANET gives out the result using Network Simulator-2. This shows a tremendous improvement in the throughput, overhead, and many more parameters which is the objective of the proposed model. 相似文献
7.
Integration of vehicular ad hoc network and fixed IP network is important to provide Internet connection and mobile data service
for vehicles. However, the unique characteristics of vehicular networks, such as linear topology and constrained movements
of vehicles, are not considered in the conventional mobility management schemes. Using conventional schemes, unnecessary management
messages are generated and the connections to roadside-installed base stations are not fully utilized. As the results, bandwidth
is wasted and data delivery ratio is not maximized. In this paper, we propose a novel mobility management scheme to integrate
vehicular ad hoc network and fixed IP networks more efficiently. The proposed scheme manages mobility of vehicles based on
street layout as well as the distance between vehicles and base stations. Utilizing the unique characteristics of vehicular
networks, the proposed scheme has substantially less mobility management overhead and higher data delivery ratio. The proposed
scheme is simulated by SUMO (a vehicular traffic simulator) and QualNet (a data network simulator). The simulation results
show that the proposed scheme reduced the mobility management overhead up to 63% and improved the data delivery ratio up to
90%. 相似文献
8.
The stochastic model assumed to govern the mobility of nodes in a mobile ad hoc network has been shown to significantly affect the network's coverage, maximum throughput, and achievable throughput-delay trade-offs. In this paper, we compare several mobility models, including the random walk, random waypoint, and Manhattan models on the basis of the number of states visited in a fixed time, the time to visit every state in a region, and the effect of the number of wandering nodes on the time to first enter a set of states. These metrics for a mobility model are useful for assessing the achievable event detection rates in surveillance applications where wireless-sensor-equipped vehicles are used to detect events of interest in a city. We also consider mobility models based on Correlated Random Walks, which can account for time dependency, geographical restrictions, and nonzero drift. We demonstrate that these models are analytically tractable by using a matrix-analytic approach to derive new, closed-form results in both the time and transform-domains for the probability that a node is at any location at any time for both semi-infinite and finite 1D lattices. We also derive first entrance time distributions for these walks. We find that a correlated random walk 1) covers more ground in a given amount of time and takes a smaller amount of time to cover an area completely than a random walk with the same average transition rate, 2) has a smaller first entrance time to small sets of states than the random waypoint and random walk models, and 3) leads to a uniform distribution of nodes (except at the boundaries) in steady state. 相似文献
9.
车载自组网络(Vehicular Ad Hoc Networks,VANET)是指道路上由车辆搭载的无线通信装置构成的一种特殊的多跳无线移动自组织网络。VANET在实现多种智能交通方面应用的同时,还能满足用户在乘车时的娱乐等舒适性的需求,近些年来已成为无线自组网络研究的新热点。总结了近些年来出现的主要VANET路由协议的核心路由机制及其优缺点,并分析了各种技术对路由协议性能的影响。其后给出了一种基于速度信息的VANET路由协议改进方法,并通过实验验证了将改进方法与GPSR协议结合可以提高路由路径的稳定性,减少了端到端的平均时延,降低了VANET网络中拓扑的高动态性对路由协议性能的影响。 相似文献
11.
Vehicle ad-hoc network (VANET) technology is a basic component of the future intelligent transportation system. With the advances in modern information society, privacy issues have become important considerations. However, most routing proposals for VANETs lack privacy support, namely anonymity or pseudonymity and unlinkability aspects. This paper presents a novel privacy addressing-based anonymous communication approach for VANETs, which prevents eavesdroppers from identifying a particular vehicle by its address. The proposed scheme is a kind of end-to-end solution, so it can potentially be extended to work with many traditional routing protocols. Finally, the simulation results show that the proposed scheme outperforms previous approaches with privacy support in terms of protocol overhead and packet latency. 相似文献
12.
We investigate connectivity in the ad hoc network formed between vehicles that move on a typical highway. We use a common model in vehicular traffic theory in which a fixed point on the highway sees cars passing it that are separated by times with an exponentially distributed duration. We obtain the distribution of the distances between the cars, which allows us to use techniques from queuing theory to study connectivity. We obtain the Laplace transform of the probability distribution of the connectivity distance, explicit expressions for the expected connectivity distance, and the probability distribution and expectation of the number of cars in a platoon. Then, we conduct extensive simulation studies to evaluate the obtained results. The analytical model that we present is able to describe the effects of various system parameters, including road traffic parameters (i.e., speed distribution and traffic flow) and the transmission range of vehicles, on the connectivity. To more precisely study the effect of speed on connectivity, we provide bounds obtained using stochastic ordering techniques. Our approach is based on the work of Miorandi and Altman, which transformed the problem of connectivity distance distribution into that of the distribution of the busy period of an equivalent infinite server queue. We use our analytical results, along with common road traffic statistical data, to understand connectivity in vehicular ad hoc networks. 相似文献
13.
In this paper we present a scalable routing protocol for ad hoc networks. The protocol is based on a geographic location management strategy that keeps the overhead of routing packets relatively small. Nodes are assigned home regions and all nodes within a home region know the approximate location of the registered nodes. As nodes travel, they send location update messages to their home regions and this information is used to route data packets. In this paper, we derive theoretical performance results for the protocol and prove that the control packet overhead scales linearly with node speed and as N
3/2 with increasing number of nodes. These results indicate that our protocol is well suited to relatively large ad hoc networks where nodes travel at high speed. Finally, we use simulations to validate our analytical model. 相似文献
14.
A mobile ad hoc network (MANET) is a dynamically reconfigurable wireless network that does not have a fixed infrastructure.
Due to the high mobility of nodes, the network topology of MANETs changes very fast, making it more difficult to find the
routes that message packets use. Because mobile nodes have limited battery power, it is therefore very important to use energy
in a MANET efficiently. In this paper, we propose a power-aware multicast routing protocol (PMRP) with mobility prediction
for MANETs. In order to select a subset of paths that provide increased stability and reliability of routes, in routing discovery,
each node receives the RREQ packet and uses the power-aware metric to get in advance the power consumption of transmitted
data packets. If the node has enough remaining power to transmit data packets, it uses the global positioning system (GPS)
to get the location information (i.e., position, velocity and direction) of the mobile nodes and utilizes this information
to calculate the link expiration time (LET) between two connected mobile nodes. During route discovery, each destination node
selects the routing path with the smallest LET and uses this smallest link expiration time as the route expiration time (RET).
Each destination node collects several feasible routes and then selects the path with the longest RET value as the primary
routing path. Then the source node uses these routes between the source node and each destination node to create a multicast
tree. In the multicast tree, the source node will be the root node and the destination nodes will be the leaf nodes. Simulation
results show that the proposed PMRP outperforms MAODV (Royer, E. M. & Perkins, C. E. (1999). In Proceedings of the ACM MOBICOM, pp. 207–218, August 1999.) and RMAODV (Baolin, S. & Layuan, L. (2005). In Proceeding of the 2005 IEEE International symposium on microwave antenna, propagation and EMC technologies for wireless communications, Vol. 2, pp. 1514–1517, August 2005.). 相似文献
15.
提出了一种改进的GPSR路由算法.该算法在选择转发节点过程中同时考虑位置和方向,进而提高转发节点选择的正确性来增加通信链路可靠性.用VanetMobisim交通仿真软件构建真实的VANETs网络城市场景,结合NS-2进行仿真研究,结果表明,和传统GPSR算法相比,改进的GPSR路由算法在端到端时延影响不大的条件下,能够有效地提高数据包传递率,降低数据丢包率.因此,改进的GPSR协议更适用于对实时性要求不高、而对可靠性要求较高的VANETs网络. 相似文献
16.
A Vehicular Ad hoc Network (VANET) is a wireless ad hoc network that is formed between vehicles on an on demand basis. In VANETs all the vehicles (nodes) are used as routers and these routers are free to move randomly and organized themselves arbitrarily. A lot of research work around the world is being conducted to design an efficient routing protocol for VANETs. In this paper, we propose a new routing method known as Peripheral node based GEographic DIstance Routing (P-GEDIR), a position-based routing protocol that takes advantage of GEographic DIstance Routing (GEDIR). It may not be possible to find node at the extreme end of the transmission range. Therefore, we have considered an area around the extreme end of the transmission range. Further a mathematical model for the protocol has been designed to determine expected number of successful hops, expected distance to the next-hop node, and expected one-hop progress. The protocol has been simulated using MATLAB. In this work, results clearly show that using the peripheral node is an advantage to maximize the performance of routing protocol in terms of average number of successful hops and expected one-hop progress. The result of P-GEDIR is compared with the existing GEDIR protocol. 相似文献
17.
研究了Ad Hoc网络中移动模型问题。针对目前Ad Hoc网络节点通常具有群组移动性的特征,提出了一种新的移动模型—高斯-马尔科夫组移动模型。通过与RWP、CGM移动模型仿真对比得出,该移动模型符合能够有效描述具有群组移动性的Ad Hoc网络,同时也表明,不同的移动模型对Ad Hoc网络路由协议性能具有很大的影响。 相似文献
18.
车载自组织网络(VANET)是一种节点迅速移动的无线自组织网络,网络的动态密度变化具有明显的特征,呈现出疏密相间的"手风琴"现象。利用汽车之间相遇的机会进行通信需要考虑到网络动态变化对传输的影响。文章利用仿真软件SUMO生成的跟踪轨迹文件,在仿真软件ONE下做网络参数的对比实验。通过模拟道路交通的网络动态密度变化,文章得到结论:最佳发送时机随网络参数不同而变化。 相似文献
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