Realistic Mobility Models for Vehicular Ad hoc Network (VANET) Simulations

Transcription

1 Realistic Mobility Models for Vehicular Ad hoc Network (VANET) Simulations Guided by Sujesh P. Lal 08MCS054, M.Tech CSE Prof. H. R. Viswakarma - SCS VIT University Vellore, TN

2 TABLE OF CONTENTS CONTENTS Page Number I. Abstract 2 II. Literature Survey 3 III. Comprehensive study on topic 4 i. IP address Configuration in VANET 5 ii. P2P Computing in design of VANET routing protocol 5 iii. Simulation of the routing protocol in VANET 6 iv. Centralized address configuration 9 IV. Inference and innovations 10 i. Routing in VANET 11 ii. Realistic mobility models 11 iii. Evaluation 12 V. Conclusion and future work 14 VI. References 15 Page 2 of 16

3 ABSTRACT Vehicular Ad-Hoc Network, or VANET, is a form of Mobile ad-hoc network, to provide communications among nearby vehicles and between vehicles and nearby fixed equipment, usually described as roadside equipment. InVANET, or Intelligent Vehicular Ad-Hoc Networking, defines an Intelligent way of using Vehicular Networking. InVANET integrates on multiple ad-hoc networking technologies such as WiFi IEEE b/g, WiMAX IEEE , Bluetooth, IRA, ZigBee for easy, accurate, effective and simple communication between vehicles on dynamic mobility. Although there are many proposed solutions for routing in VANET, it is still unclear as to what specific characteristics VANET routing protocols should possess, since none of the proposed solutions achieves optimum performance in both urban and highway, as well as sparse and dense environment. To shed light on these issues, we analyze some of the most important QoS metrics in VANET. A vehicle in VANET is considered to be an intelligent mobile node capable of communicating with its neighbors and other vehicles in the network. For configuring the vehicle with a unique address, there is a need for address reconfigurations depending on the mobility patterns; we have presented a centralized addressing scheme for VANET using DHCP (Dynamic Host Configuration Protocol). By building up a P2P overlay network on top of VANET's physical infrastructure, we effectively integrated P2P network s advantage on sustaining highly dynamic network into the design of VANET routing protocol. By deploying passive VANET routing algorithms with innovative P2P routing mechanisms, we propose a new kind of VANET routing protocol named Peer Computing based Ad hoc On Demand Vector (PAV). A detailed description of the P2P decentralized naming, route discovering, route querying and updating algorithm used in PAV is presented in this paper. The simulation results indicate that PAV has an improved routing performance in comparison with the popularly used AODV protocol. Page 3 of 16

4 I. LITERATURE SURVEY Vehicular Ad-Hoc Network (VANET) communication has recently become an increasingly popular research topic in the area of wireless networking as well as the automotive industries. The goal of VANET research is to develop a vehicular communication system to enable quick and cost-efficient distribution of data for the benefit of passengers safety and comfort. Due to the high cost of deploying and implementing such a system in real world, most of the research work in VANET is on simulations for evaluation. Random Way Point (RWP) is an earlier mobility model widely used in MANET simulation. RWP assumes that nodes can move freely in a simulation area without considering any obstacle. However, in a VANET environment vehicles are typically restricted by streets, traffic lights and obstacles. Selecting appropriate level of details in the mobility model for a VANET simulation is a critical decision. MOVE is a tool to facilitate users to rapidly generate realistic mobility model for VANET simulations. MOVE provides a facility to quickly pinpoint incorrect details and manage details overheads. This tool is developed on top of an open source micro-traffic simulator SUMO, and the output of the MOVE is a mobility trace file that contains information about realistic vehicle movement. MOVE is implemented in JAVA and runs atop of SUMO, and contains two components: the map editor and the Vehicle movement editor. Map editor used to create the road topology. We can create road topology the map can be manually created by the user, generated automatically, or imported from existing real world maps such as TIGER (Topologically Integrated Geographic Encoding and Referencing). MOVE also integrated Google Earth to create nodes in a realistic setting. In the real world scenario, the problem of address conflicts and re-configurations by using a centralized DHCP server can be solved. Address conflict can be avoided by using proper address management throughout a city or a province. We have proposed a centralized addressing scheme by exploiting the architecture of vehicular ad-hoc network. Addressing each node is an important aspect in networking. Performance evaluation is done based on three case-studies. Nodes location, density, and direction etc. affect VANET performance directly. The three case studies are based on Existence of traffic lights, Driver route choice, and Overtaking behavior. Page 4 of 16

5 II. COMPREHENSIVE STUDY ON TOPIC Development in wireless communication networks has made Inter-Vehicular Communications (IVC) and Road-Vehicle Communications (RVC) possible in Mobile Ad Hoc Networks (MANETs). This has given birth to a new type of MANET known as the Vehicular Ad Hoc Network (VANET). Governments and some car manufacturers, such as Toyota, BMW, and Daimler- Chrysler have launched some important projects for VANET, for example, Advanced Driver Assistance Systems(ADASE). The application of VANET includes the traffic control and share of multimedia information. When VANET is applied to the traffic control, it can distribute the information about the road situation, such as traffic accidents and road congestion, and is helpful in avoiding accidents. Mobility models play an important role in VANET simulations. Nodes location, density, and direction etc. affect VANET performance directly. The objective of MOVE is to inject as much detail as possible into the simulation in order to provide a more realistic mobility model. However, a truely realistic simulation is very challenging since human behavior (e.g. mood, sex, age, etc.) and unexpected road accidents are difficult to model while all of them have strong effects on vehicle movement patterns. The road topology generated by MOVE is based on the TIGER database data. The propagation model employed in our simulation is the Two Ray Page 5 of 16

6 Ground model. All nodes use MAC operating at 2Mbps. The transmission range is 250m. The routing protocol is AODV. In real world, a driver normally has to decide his moving direction at an intersection. He can choose to either go straight, turn left, or turn right. MOVE allows s user to define the turning probability of different directions at each in the Vehicle Movement Editor. IP ADDRESS CONFIGURATION IN VANET Vehicles in VANET are equipped with sensors and actuators to collect useful information and to control the behavior of the vehicle. Information sent by these sensors is collected by a centralized onboard controller. Based on the requirement, this information can also be shared with the neighboring vehicles using the onboard radio device that is DSRC (Dedicated Short Range Communications) capable. DSRC is a medium range communication service that supports inter-vehicle and vehicle-to-roadside communication. Routing in VANET has attracted a lot of interest. Some of the existing mobile ad-hoc network routing protocols like Dynamic Source Routing (DSR), Ad-hoc On Demand Distance Vector (AODV) and Optimized Link State Routing (OLSR) have been tested for vehicular ad-hoc networks. Addressing in vehicular networks could be achieved by using Dynamic Host Configuration Protocol (DHCP), which is an extensively used address configuration protocol in computer networks. Dynamic Host Configuration Protocol (DHCP) is an application layer protocol used to configure hosts in the computer communication network. DHCP supports automatic, dynamic and manual allocation of addresses. In the automatic approach, permanent addresses are assigned to the hosts by the DHCP server. In the dynamic approach, addresses are assigned by the DHCP server for a limited period of time. Page 6 of 16

7 P2P COMPUTING IN DESIGN OF VANET ROUTING PROTOCOL Different kinds of P2P network models such as Napster, Freenet and Gnutella have already been popularly used. Architecture of PAV Model The object of our design is to construct a new type of VANET routing model based on P2P computing technology. Architecture and Basic design File Discovery Service Information Administration Service File Transfer Service Communicat ion Security Service P2P Computing Based VANET Routing Algorithm P2P Overlay Network (Node Naming and Indexing) VANET Physical Network Node naming mechanism PAV adopts the similar node naming mechanism used in Chord and HASN. By adopting a consistent hashing algorithm, PAV assigns each node an m-bit node identifier (NID). NID is chosen by hashing the node's IP address, which can be used to specify the location of node in a hash ring. When a node joins the network for the first time, a NID ranges from 0 to (2m-1) will be automatically assigned to it based on the adopted hashing algorithm. Based on the large scale simulations, employed routing solution, and by implementing DSRC at physical and MAC layers, we are able to perform detailed analysis of the QoS parameters as well as the attainable unicast-based application performance over infrastructureless VANET in both highway and urban environments. SIMULATION OF THE ROUTING PROTOCOLS IN VANET According to the scheme to find route, existing MANET routing protocols can be classified into two sorts, proactive and reactive routing protocols. Destination-Sequenced Distance Vector (DSDV) protocol falls into the proactive ones. It broadcasts routing packets Page 7 of 16

8 periodically, and each node maintains the routes to all other nodes in the network. On contrary, Dynamic Source Routing (DSR) protocol is a typical reactive routing protocol, which establishes route by source node only when it needs, and the topology and routing table are also set up on demand. Reactive protocols remain then passive until the established route becomes invalid or lost. Selecting appropriate level of details in the mobility model for a VANET simulation is a critical decision. Developed a tool MOVE (Mobility model generator for Vehicular networks) to facilitate users to rapidly generate realistic mobility models for VANET simulations. MOVE provides an environment that allows the user to quickly pinpoint incorrect details and manage details overhead. Our tool is built on top of an open source micro-traffic simulator SUMO. MOVE allows user to conveniently incorporate realistic road maps into the simulation. In addition, by providing a set of GUI that automate the simulation script generation. Architecture of MOVE In a typical VANET scenario, numerous concurrent communication sessions will take place between different sender/receiver pairs for unicast applications. Given the high cost of deploying actual equipment in the vehicles, real life test beds for VANET research are extremely rare. We conducted simulations using the Jist/SWANS simulator with the STRAW mobility model. JiST (Java in Simulation Time) is a discrete event simulation environment, and SWANS (Scalable Wireless Ad Hoc Network Simulator) is a publicly available Java-based scalable Page 8 of 16

9 wireless network simulator. STRAW (Street Random Waypoint) is a vehicular mobility model, built on top of the JiST/SWANS platform, that constrains the node movement to real U.S. streets (based on the U.S. Census Bureau s TIGER data). A Tiger map and its Visualization Tiger Map Simulation Visualization The roadway portion we used was approximately 43.5 km long, with 3 lanes per direction. Within the simulation, we chose two vehicles as the observed vehicles (vehicles selected to be the sender/receiver pair in a given simulation run). For these vehicles, we specified initial placement, speed, and travel direction. We distinguished same direction and opposite direction scenarios. In the same direction scenarios, the observed vehicles were initially placed next to each other and moved in the same direction. In the opposite direction scenarios, the observed vehicles were placed approximately 10 km apart and moved towards each other. To have a greater control over the simulation, we specified the relative speed (difference between the speeds) of the two observed vehicles as 0, 5, 10, and 15 m/s in the same direction and as 40, 50, 60, and 70 m/s in the opposite direction scenarios. Performance metrics 1. Connection duration 2. End-to-end delay 3. Jitter 4. Packet delivery ratio Page 9 of 16

10 The values of delay and jitter in VANET can satisfy the requirements of most applications, while PDR and connection duration are both highly dependent on the vehicle density and the specific environment, and the connection duration is also closely related to the relative speed of vehicles. The results also confirmed our initial assumptions regarding the locality of interest for applications in VANET; communication over large area will not be possible without the use of infrastructure. CENTRALIZED ADDRESS CONFIGURATION At first we assume that there is a central authority to control address distribution and management. This responsibility can be taken up by vehicle manufactures or government agencies. DHCP servers are installed in cities to cover a large area or an entire city depending on vehicle densities. Redundant DHCP servers can be installed in order to provide fault tolerance. Some of these servers might be capable of extending the lease for an IP address assigned by a distant DHCP server. Such responsibilities can be assigned and managed by the central authority. Access to these servers is provided by roadside units. Roadside units are equipped with access points that provide Internet access to vehicles. These roadside units act as an interface between vehicles and DHCP servers that dynamically assign IP addresses to vehicles. Page 10 of 16

11 III. INFERENCE AND INNOVATIONS The goal of VANET research is to develop a vehicular communication system to enable quick and cost-efficient distribution of data for the benefit of passengers safety and comfort. It is important to use a realistic mobility model so that results from the simulation correctly reflect the real-world performance of a VANET. The main goal of VANET is providing safety and comfort for passengers. To this end a special electronic device will be placed inside each vehicle which will provide Ad-Hoc Network connectivity for the passengers. This network tends to operate without any infra-structure or legacy client and server communication. Each vehicle equipped with VANET device will be a node in the Ad-Hoc network and can receive and relay others messages through the wireless network. Collision warning, road sign alarms and in-place traffic view will give the driver essential tools to decide the best path along the way. There are also multimedia and internet connectivity facilities for passengers, all provided within the wireless coverage of each car. Automatic payment for parking lots and toll collection are other examples of possibilities inside VANET. Most of the concerns of interest to MANets are of interest in VANets, but the details differ. Rather than moving at random, vehicles tend to move in an organized fashion. The interactions with roadside equipment can likewise be characterized fairly accurately. And finally, most vehicles are restricted in their range of motion, for example by being constrained to follow a paved highway. Vehicular Ad-hoc Networks are expected to implement variety of wireless technologies such as Dedicated Short Range Communications (DSRC) which is a type of WiFi. Other candidate wireless technologies are Cellular, Satellite, and WiMAX. Vehicular Ad-hoc Networks can be viewed as component of the Intelligent Transportation Systems (ITS). Vehicular Networks are an envision of the Intelligent Transportation Systems (ITS). Vehicles communicate with each other via Inter-Vehicle Communication (IVC) as well as with roadside base stations via Roadside-to-Vehicle Communication (RVC). The optimal goal is that Page 11 of 16

12 vehicular networks will contribute to safer and more efficient roads in the future by providing timely information to drivers and concerned authorities. The main goal of VANET is providing safety and comfort for passengers. To this end a special electronic device will be placed inside each vehicle which will provide Ad-Hoc Network connectivity for the passengers. This network tends to operate without any infra-structure or legacy client and server communication. Each vehicle equipped with VANET device will be a node in the Ad-Hoc network and can receive and relay others messages through the wireless network. Collision warning, road sign alarms and in-place traffic view will give the driver essential tools to decide the best path along the way ROUTING IN VANET Routing in VANETs are Often position based addressing. GeoBroadcast: send to all nodes within a region All cars in the area of Ulm/B10: Accident on Adenauer bridge when heading towards Neu-Ulm. GeoAnycast: send to arbitrary node within a region How are traffic conditions three km ahead?. The next technique is Fleetnet Routing Protocol which address surrounding nodes. Here direct flooding of message in target region ( Area-Forwarding ) is carried out and in address remote nodes it first does the line-forwarding, and then areaforwarding is done. REALISTIC MOBILITY MODELS FOR VANET SIMULATIONS Several communication networking simulation tools already exist to provide a platform to test and evaluate network protocols, such ns-2, OPNET and Qualnet. However, these tool are designed to provide generic simulation scenarios without being particularly tailored for applications in the transportation environment. On the other hand, in the transportation arena, simulations have also played an important role. A variety of simulation tools such as PARAMICS, CORSIM, VISSIM etc have been developed to analyze transportation scenarios at the micro- and macro-scale levels. MOVE is currently implemented in Java and runs atop an open-source micro-traffic simulator SUMO. MOVE consists of two main components: the Map Editor and the Vehicle Page 12 of 16

13 Movement Editor. The objective of MOVE is toinject as much detail as possible into the simulation in order to provide a more realistic mobility model. EVALUATION Figure 1 shows the distribution of the number of neighboring nodes when ten traffic lights are included in the simulations. Our results show that each node has twice the number of neighboring nodes when traffic lights are simulated, as compared to the case when traffic lights are not simulated. Figure 1 Figure 2 Figure 2 shows the packet delivery ratio is improved when the traffic lights are simulated. Note that in this simulation the distance between two adjacent traffic lights is shorter than the given radio range. In addition, we observe that the number of packet collisions increases as we increase the number of traffic sources. As a result, the packet delivery ratio decrease when there are more traffic sources.to understand the effect of inter-cluster distance on the simulations results, increase the distance between two adjacent traffic lights (from 200m to 400m) so that the intercluster distance is larger than the effective radio distance. As shown in Figure 3, in this scenario we observe frequent link breakage between two adjacent clusters which significant degrades the network performance. Page 13 of 16

14 Figure 4shows that we find that different choices of route directions can significantly change the simulation results (the x-y-z notation in Figure 4 means that the car has x% of chance to turn left, y% to go straight and z% to turn right). In real world, a driver normally has to decide his moving direction at an intersection. He can choose to either go straight, turn left, or turn right. MOVE allows s user to define the turning probability of different directions at each intersection (e.g. 0.5 to turn left,0.3 to go straight and 0.2 to turn right) in the Vehicle Movement Editor. Page 14 of 16

15 IV. CONCLUSION AND FUTURE WORK The paper studied the application of VANET to the city road traffic control. The results have some value in the research and application of VANET to traffic control, and the design of a more suitable routing protocol for VANET is the next step of work. The tool MOVE which is based on an open source micro-traffic simulator SUMO. MOVE allows user to quickly generate realistic mobility models for vehicular network simulations. MOVE is publicly available and can be downloaded via the following URL - It is shown that the details of a mobility model such as the existence of traffic lights, driver route choice and car overtaking behavior can have a significant impact on the simulation results. The movements of vehicles are based on static configurations defined in the Vehicle Movement Editor. Based on the study of synergies between P2P network and VANET, proposed a new type of VANET routing protocol named PAV. By building up a P2P overlay network on top of VANET's physical infrastructure, PAV seamlessly integrates the functions of p2p overlay routing protocols operating in a logical namespace with those of VANET routing protocols operating in a physical namespace. Compared to the other ad hoc networks, due to its highly dynamic nature a VANET environment clearly presents great challenges in designing appropriate routing protocols. The results obtained are valuable because they define the upper performance bound for unicast routing over DSRC-enabled VANET in both urban and highway environments with typical vehicle speeds and traffic densities. In the future, we plan to further elaborate on the redundant routes in urban and highway environment in order to determine the optimum rebroadcast probabilities for selective broadcast routing protocols in these environments. We are also going to analyze the QoS metrics in urban environment with respect to close proximity neighbors (i.e., one and two hop neighbors), in order to see whether restricting the geographical range of communication can assure increased PDR and connection duration even without infrastructure support. Furthermore, extending the employed routing scheme to support broadcast/multicastwould provide a useful insight into the potential performance of many safety and non-safety applications in VANET that require such communication. Page 15 of 16

16 REFERENCES [1] Kun-chan Lan and Chien-Ming Chou, Realistic Mobility Models for VANET Simulations. [2] SUN Xi, LI Xia-miao, Study of the Feasibility of VANET and its Routing Protocols. [3] Brijesh Kadri Mohandas, Ramiro Liscano, IP Address Configuration in VANET using Centralized DHCP. [4] Song Haibin, Meng Qi, Men Aidong P2P Computing in Design of VANET Routing Protocol. [5] Mate Boban, Geoff Misek, and Ozan K. Tonguz, What is the Best Achievable QoS for Unicast Routing in VANET? [6] Bojin Liu, Behrooz Khorashadi, Haining Du, Dipak Ghosal, Chen-Nee Chuah, and Michael Zhang, VGSim: An Integrated Networking and Microscopic Vehicular Mobility Simulation Platform. Page 16 of 16