# Dynamic Multiple Junction Selection Based Routing Protocol for VANETs in City Environment
## 1 Introduction  
The emerging Vehicular Ad-hoc Networks (VANETs) is getting a spotlight from entities like academicians, research institutes, and industries because it is envisioned to play a very important role for the future transportation system. It aims at enhancing the driving experience of the users by playing a crucial role in developing Intelligent Transportation System (ITS) and road safety by providing road conditions and vehicular traffic information to the drivers. For the safety of drivers and regulating the flow of vehicles, the drivers have to be alerted to unwanted traffic accidents, traffic congestion, road conditions, and other associated features. The main objective of VANETs is to address these issues by providing the exact and timely information to the drivers [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12]. In VANETs, nodes are self-organized and capable of communicating in an infrastructure-less environment [1; 2; 3; 4; 5; 13; 14]. The integration of advanced wireless technologies in vehicles helps them to communicate without any infrastructure, which reduces the cost of hefty infrastructure deployment. For the wireless access in a vehicular environment, IEEE 802.11 committee has developed a standard named as IEEE 802.11p. For Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications,the Federal Communications Commission (FCC) has allocated a bandwidth of 75 MHz in 5.9 GHz band for licensed Dedicated Short Range Communication (DSRC). Each vehicle exchanges information with other vehicles as well as roadside units within their radio ranges by using the allocated bandwidth by FCC [1; 2; 3; 13; 14]. Also, various significant projects like CarTALK2000(Car Talk 2000) [15], C2 CCC(Car 2 Car Communication Consortium) [16], California PATH(California Partners for Advanced Transportation Technology) [17], FleetNet [18], DEMO 2000 by Japan Automobile Research Institute (JSK) [19], Chauffeur in EU [20] and Crash Avoidance Metrics Partnership (CAMP) [19] are initiated by different firms for developing vehicular communication. VANETs are an offshoot of Mobile Ad hoc Networks with certain differentiating characteristics. For instance, the nodes in MANETs (Mobile Ad-hoc Networks) have random movements, but the movement of vehicular nodes is constrained by predefined roads. Traffic control system, speed barriers, and congestion on the road also affect the speed and mobility pattern of vehicles. The vehicles can be equipped with transceivers having longer transmission ranges, broad on-board storage capacities, digital maps, and sensors for revealing vehicle states. Unlike MANETs, limited battery, processing power, and storage do not make an issue in VANET due to the availability of rechargeable sources of energy [11; 12; 13; 14; 21; 22]. There are a lot of technical challenges in the design of effective vehicular communications. One of them is to design an efficient routing strategy capable of computing shortest rich density optimal path. Finding such a path is a challenge because of the high mobility of the nodes, the intermittent connectivity, and the uneven distribution of vehicular nodes, which varies with time and location. The nodes in one area may be sparsely connected while in another area they can be densely connected. While, at the same time, the predictable mobility and mobility restrictions are helpful in establishing routes [2; 3; 8]. Traditional MANETs routing protocols are unable to handle these issues. For routing in VANETs, researchers have evaluated various well-known MANETs routing protocols but they have concluded that MANETs routing protocols do not fit well in VANETs setting [23; 24; 25; 26]. In the existing literature, most of the well-known routing protocols specifically designed for VANETs establish routing path by considering immediate junction/street from source to destination.