IMPROVED PACKET FORWARDING APPROACH IN VEHICULAR AD HOC NETWORKS USING RDGR ALGORITHM
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15-10-2010, 01:01 PM
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VANETs (Vehicular Ad hoc Networks) are highly mobile wireless ad hoc networks and will play an important role in public safety communications and commercial applications. Routing of data in VANETs is a challenging task due to rapidly changing topology and high speed mobility of vehicles. Position based routing protocols are becoming popular due to advancement and availability of GPS devices. One of the critical issues of VANETs are frequent path disruptions caused by high speed mobility of vehicle that leads to broken links which results in low throughput and high overhead . This paper argues the use of information on vehicles’ movement information (e.g., position, direction, speed of vehicles) to redict a possible link-breakage event prior to its occurrence. So in this paper we propose a Reliable Directional Greedy routing (RDGR), a reliable position based routing approach which obtains position, speed and direction of its neighboring nodes from GPS. This approach incorporates potential score based strategy, which calculates link stability between neighbor nodes in distributed fashion for reliable forwarding of data packet.
Recent advances in wireless technologies have made inter-vehicular communications (IVC) possible in mobile ad hoc networks (MANETs) and this has given birth to a new type of MANET known as the vehicular ad hoc networks (VANETs). Internetworking over VANETs has been gaining a great deal of momentum over the past few years. VANETs is a form of mobile ad hoc network providing communications among nearby vehicles as well as between vehicles and nearby fixed equipment, usually described as roadside equipment. Vehicles are becoming “computer networks on wheels” and acts as mobile nodes of the network. VANET technology integrates ad hoc network, wireless LAN (WLAN) and cellular technology to achieve intelligent Inter-Vehicle Communications (IVC) and Roadside-to-Vehicle Communications (RVC).
VANETs are a special case of MANETs and both are characterized by the movement and self-organization of the nodes. However, unlike MANETs, the mobility of vehicles in VANETs is, in general, constrained by predefined roads. Vehicle velocities are also restricted according to speed limits, level of congestion in roads, and traffic control mechanisms. In addition, given the fact that future vehicles can be equipped with devices with potentially longer transmission ranges, rechargeable source of energy, and extensive onboard storage capacities, processing power and storage efficiency are not an issue in VANETs as they are in MANETs. From these features, VANETs are considered as an extremely flexible and relatively “easy-to-manage” network pattern of MANETs. Due to recent developments in the VANET field, a number of attractive applications, which are unique for the vehicular setting, have emerged. VANET applications include onboard active safety systems that are used to assist drivers in avoiding collisions and to coordinate among them at critical points such as intersections and highway entries. It is beneficial in providing intelligent transportation system (ITS) as well as drivers and passenger’s assistant services.
Safety systems may intelligently disseminate road information, such as incidents, real-time traffic congestion, high-speed tolling, or surface condition to vehicles in the vicinity of the subjected sites. This helps to avoid platoon vehicles and to accordingly improve road capacity. With such active safety systems, the number of car accidents and associated damage are expected to be largely reduced. In addition to the aforementioned safety applications, IVC communications can also be used to provide comfort applications. The latter may include weather information, gas station or restaurant locations, mobile e-commerce, infotainment applications, and interactive communications such as Internet access, music downloads, and content delivery.
VANETs have similar or different radio interface technologies, employing short-range to medium-range communication systems. The radio range of VANETs is several hundred meters, typically between 250 and 300 meters. In US, the Federal Communications Commission (FCC) has allocated 75 MHz in 5.9 GHz band for licensed Dedicated Short Range Communication (DSRC) for vehicle-to-vehicle and vehicle to infrastructure communications. Recently, the promises of wireless communications to support vehicular applications have led to several research project and implimentations around world. National Highway Traffic Safety Administration (NHTSA) and the automotive OEMs created the Vehicle Safety Communication Consortium (VSCC) to promote V2V networking for safety.
Governments and prominent industrial corporations, suchas Toyota, BMW, and Daimler–Chrysler, have launched important project and implimentations for IVC communications. Advanced Driver Assistance Systems (ADASE2) , Crash Avoidance Metrics Partnership (CAMP) , Chauffeur in EU ,CarTALK2000 , FleetNet [5 , California Partners for Advanced Transit and Highways (California PATH) ,DEMO 2000 by Japan Automobile Research Institute (JSK), Electronic Toll Collection service (ETC), Advanced Cruise-Assist Highway System (AHS), Vehicle Information and Communication System (VICS) , AutoNet , Path , C2C-CC project and implimentation  in Europe, and the related project and implimentations include Safety Support , PReVENT project and implimentation , Network on Wheels project and implimentation , COMeSafety  etc are few notable examples. The Internet ITS (Intelligent Transportation Systems) Consortium  in Japan is one of the samples of VANETs project and implimentations. These project and implimentations are a major step toward the realization of intelligent transport services. The design of effective vehicular communications poses a series of technical challenges. Guaranteeing a stable and reliable routing mechanism over ANETs is an important step toward the realization of effective vehicular communications. Existing routing protocols, which are traditionally designed for MANET, do not make use of the unique characteristics of VANETs and are not suitable for vehicle-to-vehicle communications over VANETs.
Indeed, the control messages in reactive protocols and route update timers in proactive protocols are not used to anticipate link breakage. They solely indicate presence or absence of a route to a given node. Consequently, the route maintenance process in both protocol types is initiated only after a link-breakage event takes place. When a path breaks, not only portions of data packets are lost, but also in many cases, there is a significant delay in establishing a new path. This delay depends on whether another valid path already exists (in the case of multipath routing protocols) or whether a new route-discovery process needs to take place. The latter scenario introduces yet another problem. In addition to the delay in discovering new paths, flooding required for path discovery would greatly degrade the throughput of the network as it introduces a large amount of network traffic. In a highly mobile system such as VANET, where link breakage is frequent, flooding requests would largely degrade the system performance due to the introduction of additional network traffic into the system and interruption in data transmission.