# A Performance Analysis of VANETs Propagation Models and Routing Protocols
## 2 Literature Review
Several literature contributions have emphasized the use of MIMO techniques to exploit multipath. In future vehicular networks, massive MIMO with beam-forming is being investigated as a potential wireless communication technique. It should be noted that the mixed noise in a complex environment such as a vehicular network is prevalent using MIMO [18]. In contrast to the literature study, this work attempts to analyze the performance of OLSR, AODV, and DSDV protocols while considering propagation models as a constant. The performance of various propagation models is compared, considering the OLSR as a routing protocol. For interfacing MAC and PHY layer, 802.11p is assumed to remain steady throughout the simulation. The performance metrics chosen for the analysis are PDR, throughput, delay, average routing goodput, and MAC/PHY overhead. Greedy Perimeter Coordinator Routing (GPCR), Zone Routing Protocol (ZRP), Vehicle-Assisted Data Delivery (VADD), Greedy Perimeter Stateless Routing (GPSR), Inter-Vehicle Geocast (IVG), Geographic-Delay Tolerant Network (Geo-DTN), Contention Based Forwarding (CBF), DV-CAST (Distribution Vehicular broadCAST) are some of the VANET routing protocols for efficient communication. Table 1 presents a comparative study of some routing protocols that can be implemented for the VANET scenario based on the type of protocol, type of communication, routing type, and type of data transmission approach. The GPCR is based on a predetermined path; this protocol implements a restricted greedy forwarding method. Coordinator nodes (nodes on junctions) are preferred over non-coordinator nodes even if the latter is not the geographically closest nodes to the destination. It considers the buffer size of the queue and the distance of nodes from the destination. ZRP offers both proactive and reactive advantages, designed to deal with excess bandwidth of proactive protocol and inefficient reactive protocol flooding. It maintains a topology with a node as the center of each zone. By doing this, routing information is immediately available within each zone. It provides the most efficient routing from the local routing information of the zones for the destinations outside the zone where it uses a route discovery method. VADD provides service using predictable vehicle mobility to implement the concept of carry forward by multihop data delivery. Based on beacon information, the GPSR selects the node closest to the final destination. Depending on the scenario, it selects a node for packet transmission by using greedy forwarding or perimeter forwarding. The IVG geo-cast routing protocol relays safety information, such as an accident, to all nodes that are located on the highway. Timer-based mechanisms allow each node of this protocol to receive packets and rebroadcast them once a timer expires. During periodic broadcasts, the IVG protocol reduces fragmentation between members of multicast groups. Heterogeneous networks like that of VANET can benefit from the DTN routing protocol. DTN protocols utilize the store-carry-forward mechanism for packet forwarding to overcome the challenge of frequent disconnection. The CBF technique is used in Intelligent Transportation Systems (ITS) to disseminate messages for traffic safety applications. This protocol implements a contention mechanism based on the priority of packets. DV-Cast is