# Enhancing OLSR Protocol by an Advanced Greedy Forwarding Mechanism for VANET in Smart Cities
## 1 Introduction  
The ITS enhanced the well-being and driving surroundings with the integration of information technology in transport systems. Thus, it would be a great opportunity if vehicles could communicate directly with each other, provided that they are within range. On the other hand, they must react as a relay to reach far destinations, hence the VANET network.  
Today, many research works have taken interest in Ad Hoc wireless networks due to their low cost when there is a need to communicate in the absence of infrastructure. To improve road safety [1] or ensure internet access for passengers, road safety systems have emerged to ensure exchange inter-vehicle and fixed vehicle infrastructure information in a wireless network. Thousands of researchers [2; 3; 4] have been interested in this area and have tried to adapt the routing protocol for MANET to the VANET network because most traditional routing protocols of MANETs cannot directly apply to VANET. To reach this goal, we must improve the communication between vehicles to ensure information transmission by taking into account the VANET features. In other words, we must improve the routing process.  
Routing protocols must ensure low control overhead [5], low complexity, and must enhance broadcast capability. Following the criteria of the urban environment, the design of a routing protocol in VANET to ensure vehicle-to-vehicle (V2V) communication meets other challenges [6]. In particular, the high mobility of vehicles in this network requires adapting routing information to frequent changes in the topology. Therefore, we must reduce the convergence time for routing algorithms to find the path from the source to the destination that can enhance the end-to-end delay and minimize the latency time to discover neighbors.  
It is required to ensure communication integrity owing to the nature of information, which can reduce accidents and save lives, hence the importance of the packet delivery ratio. In addition, the end-to-end delay constraint of real-time applications and the retransmissions used for error control should be delay-constrained. The aim of this research is to improve the end-to-end delay of our network and its packet delivery ratio. Otherwise, the information will become obsolete.  
Thus, this paper contributes to the following areas:  
* We start by presenting the theoretical framework that includes a literature review of the routing protocol in the VANET environment, which is part of the smart cities challenges.
* We present an efficient implementation of the Advanced Greedy Forwarding algorithm \"GFA\", which overcomes the problem of stationary vehicles. The source node forwards incoming messages to a selected node according to a score based on its position and speed.
* We study the benefits of GFA compared to GF in terms of the end-to-end delay and packet delivery ratio using the NS3 simulator.
* We improve the OLSR protocol by introducing a GFA mechanism to collect information that is used in the proposed score to select the best way to the destination.
* We compare our proposed Greedy-OLSR (G-OLSR) to OLSR and we note that our protocol outperforms OLSR in terms of the end-to-end delay and packet delivery ratio.  
The rest of this paper is organized as follows. In the next section, we discuss the taxonomy of routing protocols for the VANET environment, their advantages, and their limitations, and related work is briefly presented. This is followed by the proposed routing strategy in the following section. The experimental results are presented in the next section. Finally, we conclude with a perspective.