Vehicular Reactive Routing Protocol - VRR Broadcasting

VRR Broadcasting

This algorithm is based on combination of three approaches

• Neighbour elimination family: receiving nodes themselves decide to rebroadcast data or not on base of network coverage. If all nodes in transmit range of receiver node are covered by the information, then the receiver node does not rebroadcast. If some node is not covered by the information in transmit range of the node then the node prepares data to rebroadcast.
• Source-dependent dominating sets: The principle is that a sender determines for a small subset of neighbours which is called multipoint relay (MPR). Only nodes inside the subset can rebroadcast information from the source.
• Probability: where probability depending on the distance between a transmitter and a receiver. A Higher probability is chosen for node further from a source and vice versa with a lower probability for closer nodes.

Principle of VRR Broadcasting simply like that: A transmitter sends a broadcast data.

• If receiving node is chosen as MPR node by transmitter, it sets up shortest backoff time (waiting time before rebroadcasting).
• If receiving node is not chosen as MPR node by transmitter, it sets up backoff time depend on its mobility behaviour (distance from a transmitter, speed and vector of motion).
• If receiving node calculates that its neighbour's nodes are already covered by broadcast information, then the node doesn't rebroadcast.

An advantage of VRR Broadcasting approach is that all receiving nodes have some opportunity to rebroadcast information (not only MPR nodes), but only a few nodes have the best opportunity (i.e. the shortest backoff time) for rebroadcasting. Another advantage is that in the case of the multipoint relay node not always receiving the broadcast due to collisions (in a dense busy network) then other nodes who overhear can transmit the information instead.