# Improved Road Segment-Based Geographical Routing Protocol for Vehicular Ad-hoc Networks
## 1 Introduction  
Real-time data communication among on-road vehicle nodes can be enabled by realizing vehicular ad hoc networks (VANETs) with or without the support of existing infrastructure alongside roads [1]. This networking field has gained significant popularity among researchers and automobile industries because of its different types of advanced traffic applications. Most of the applications in this area offer convenience and improvement in road safety. In addition, the safety applications contain information to alert drivers in case of accidents, traffic congestion, repair work, emergency braking, available parking spaces, and the presence of police radar and emergency response vehicles [2]. Vehicle nodes are taking advantage of new and advanced networking technologies, and they are reducing thedeployment cost of on-road wireless communication devices. Indeed, by the installation of sensor node enabled communication kit in vehicles or at the edges of roads and in control centers, vehicular communications can alert drivers for possible dangers on the road ahead in advance. Additionally, to improve data communication and road safety, vehicular networks offer new services to road users for more convenience and road safety [3]. Several research projects related to road safety have been running in academia and industries, where different electronic devices are installed in vehicle nodes to develop such a network including radars, cameras, and global positioning system (GPS) tracking systems. Vehicular nodes contain an on-board unit (OBU) that is attached to the vehicle to enable communication with other OBUs and roadside units (RSUs). An RSU refers to a node or base station installed on the roadside that provides connectivity among vehicle nodes. It allows easy access to the network and provides further connection to the main network control station. Two types of vehicular communications are mainly realized in VANETs including vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) [4]. The design of information dissemination-centric routing protocols is one of the most challenging tasks in realizing VANETs due to the dynamic vehicular network environment when considering the higher mobility of vehicular nodes and unpredictable vehicular network topologies [5]. Because of these constraints, the exchanged network information among nodes becomes outdated quite frequently. It results in network disconnections and packet dropping issues in information dissemination. These issues have been addressed in different vehicular network routing protocols that have considered limited network parameter predictions [6]. Vehicle node movement in VANETs is typically restricted in two-way roads and streets. The routing protocols that use physical location information of the nodes received from GPS and existing road or street map knowledge are the best to consider for routing decisions in the vehicular environment [7]. There are still various challenges for the deployment of VANETs and the development of related traffic applications such as the unstable movement of traffic that results in multi-path topologies and insufficient physical network deployment in terms of lack of RSUs [8]. Thus, the higher mobility of vehicle nodes and unpredictable network topologies transform VANETs into highly dynamic network environments. For predicting network topology, several incremental packets increase the network overhead in a vehicular traffic environment. The frequent network disconnections mostly happen in a sparse network environment where the distance between vehicle nodes is longer than dense traffic areas [9]. Furthermore, obstacles, like the different sizes of vehicles and high rise buildings, are some other issues that lead to network disconnection. It is little easy to establish a communication path between vehicles to communicate in a dense traffic network environment. In contrast, in lower vehicle density environments, frequent network disconnections lead to network overhead and stale packets [10].