A Survey of Geographic Routing Protocols for Vehicular
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This document summarizes and classifies several geographic routing protocols for vehicular ad hoc networks (VANETs). It discusses unicast routing protocols like GPSR, GSR, and GPCR that use greedy forwarding and perimeter routing. It also covers broadcast protocols like UMB and cluster-based protocols like COIN. Finally, it examines geocast routing protocols for disseminating messages to nodes within a specified geographic region, such as IVG, Cached Geocast, and Abiding Geocast. The document concludes that the optimal protocol depends on the routing type (unicast, broadcast, geocast) and the road scenario (city vs highway).
A Survey of Geographic Routing Protocols for Vehicular
- 1. A Survey of Geographic Routing Protocols for Vehicular Ad Hoc Networks (VANETs) By Jesus Gabriel Balderas Lopez
- 2. Problem definition - Routing in VANETs is a challenge due to mobility of the nodes and fast change in the topology of the network. - Position-based routing is a good solution for VANETs because you know where is located the intended receiving node, the sending node, and intermediate nodes.
- 3. Classification By routing type of the protocol (how the protocol uses the position information): Unicast: GPSR(Packet forwarding), GSR(Packet forwarding), GPCR(Packet forwarding) , A-STAR(Packet forwarding), COIN(Cluster formation), LORA_CBF(Packet forwarding). Broadcast: UMB(Packet forwarding), BROADCOMM(Formation of cells), V-TRADE/HV-TRADE(Classify forwarding group). Geocast: IVG(Packet forwarding), Cached Geocast(Packet forwarding), Abiding Geocast(Packet forwarding)
- 4. Unicast protocols (GPSR) Greedy Perimeter Stateless Routing (GPSR): One of the best known position-based protocols. It combines greedy routing with face routing. The geographic information is used for packet forwarding.Â
- 5. Unicast protocols (GSR) Geographic Source Routing (GSR): The algorithm needs global knowledge of the city topology (street map). The sender determines the junctions that have to be traversed by the packet using the Dijkstra's shortest path algorithm. Forwarding between junctions is done in a position-based fashion. GSR was designed for city environments
- 6. Unicast protocols (GPCR) Greedy Perimeter Coordinator Routing (GPCR): The nodes at a junction in the street follow a natural planar graph. Thus, a restricted greedy algorithm can be followed as long as the nodes are in a street. Junctions are the only places where actual routing decisions are taken. Therefore packets should always be forwarded to a node on a junction (Coordinator).
- 7. Unicast protocols (GPCR cont.)
- 8. Unicast protocols (A-STAR) Anchor-based Street and Traffic Aware Routing (A-STAR): Designed for city environments. A-STAR uses the street map to compute the sequence of junctions (anchors) through which a packet must pass to reach its destination. The difference between A-STAR and GSR is that A-STAR computes the anchor paths with traffic awareness. It is possible by using statistically rated maps (counting the number of city bus routes on each street) or dynamically rated maps (monitoring the latest traffic conditions). In recovery state, to prevent other packets from traversing through the same void area, the street at which the local minimum ocurred is marked as "out of service".
- 9. Unicast protocols (COIN) Clustering for Open Inter-vehicular communication Networks (COIN): It is a Cluster-Based Routing protocol. The geographic information is used for cluster formation. Â Cluster head election is based on vehicular dynamics and driver intentions, instead of ID or relative mobility as in classical clustering methods.
- 10. Unicast protocols (LORA_CBF) LORA_CBF is also a cluster-based routing protocol. Packets are forwarded from a source to the destination by protocol similar greedy routing. If the location of the destination is not available, the source will send out the location request (LREQ) packets. Only cluster heads and gateways will disseminate the LREQ and LREP (location Reply) message.Â
- 11. Broadcast protocols The simplest way to implement a broadcast service is flooding in which each node re-broadcast messages to all of its neighbors except the one it got this message from. Flooding guarantees the message will eventually reach all nodes in the network. Flooding performs relatively well fro a limited small number of nodes and is easy to be implemented. But when the number of nodes in the network increases, the performance drops quickly.
- 12. Broadcast protocols (BREADCOMM) In BROADCOMM, the highway is divided into virtual cells, which moves as the vehicles move. The nodes in the highway are organized into two level of hierarchy: the first level includes all the nodes in a cell; the second level is represented by the cell reflectors, which are a few nodes usually located closed to the geographical center of the cell. This protocol only works with simple highway networks.
- 13. Broadcast protocols (UMB) Urban Multi-Hop Broadcast protocol (UMB) is designed to overcome interference, packet collision, and hidden nodes problems during message dissemination in multihop broadcast. The sender try to select the furthest node in the broadcast direction to assign the duty of a forwarding and acknowledging the packet without any a priori topology information. Repeaters are installed in the intersections to forward the packets to all road segments.
- 14. Broadcast protocols (V-TRADE & HV-TRADE) Vector-based TRAcking DEtection (V-TRADE) and History-enhanced V-TRADE (HV-TRADE): They are GPS based message broadcasting protocols. Based on position and movement information, their methods classify the neighbors into different forwarding groups. For each group, only a small subset of vehicles (called border vehicles) is selected to rebroadcast the message.
- 15. Geocast Routing Geocast routing is basically a location-based multicast routing. The objective of a geocast routing is to deliver the packer from a source node to all other nodes with a specified geographic region (Zone of Relevance, ZOR)
- 16. Geocast Routing (IVG) Inter-Vehicles Geocast protocol (IVG) broadcast an alarm message to all the vehicles being in risk area based on defer time algorithm in a highway. When a node receives a packet, it does not rebroadcast it immediately but has to wait some waiting time to make a decision about rebroadcast.
- 17. Geocast Routing (Cached Geocast) The main idea of the cached greedy geocast inside the ZOR is to add small cache to the routing layer that holds those packets that a node cannot forward instantly due to a local minimum. When a new neighbor comes into reach or known neighbors change their positions, the cached message can be possibly forwarded to the newly discovered node.
- 18. Geocast Routing (Abiding geocast) The packets need to delivered to all nodes that are sometime during the geocast lifetime (a certain period of time) inside the geocast destination region.Â
- 19. Conclusions There are several options of geographic routing protocols for VANETs depending on the routing type (unicast, broadcast, geocast), the scenario (city environment or highway). There is no protocol that works optimally in both city environment and highway.
- 20. Questions?