Functioning

There are two main steps involved in how opportunistic routing works:

• Selection of potential forwarders between the source and destination
• Prioritization among these forwarders, where various metrics play a role.

As mentioned above, instead of pre-selecting a single specific node to be the next-hop as a forwarder for a packet, multiple nodes can potentially be selected. Thus the source can use multiple paths to deliver the packets to the destination.

When the current node transmits a packet, all the candidates that receive the packet successfully will coordinate with each other to determine which one would actually forward the packet, while the other nodes will simply discard the packet. This method minimizes the chance of multiple nodes transmitting the same packet, which could lead to collision.

Consider an example. The source node S has 3 intermediate nodes with packet delivery probability of 20%. Each node has packet delivery probability of 78% to the destination. Traditional routing will chose only one path for forwarding the data, while Opportunistic Routing will consider all the paths.

Node S forwards data packets to multiple nodes using broadcasting. Each edge has a different probability weight based on metrics. Candidate nodes are {A, B, C}. Based on this set, each path from A to D is tried, whoever reaches the destination first is the chosen path. Notice, how the process takes place dynamically.

Forward Batch: It is a group of packets forwarded by a node to the next hop node.

Dynamic Relay Node can be used to forward the packet, to increase the transmission reliability and network throughput.

Opportunistic routing is a technique, that makes use of the broadcasting nature of wireless networks i.e. when one node transmits, multiple other nodes can listen to the data transmitted. Rather than pre-selecting a single next hop, the route is determined dynamically based on which node is closest to the destination and the forwarding of data is done by the same. A core aspect of this method is determining the set of potential forwarders and ranking them based on certain parameters. This technique enhances the effectiveness, data transfer rate, and reliability of wireless networks.

Traditional routing consists of predetermined fixed paths, which might not always be optimal because of fluctuations in link quality, interference, and mobility and may not be available for transmission at all times. Unlike traditional routing, in Opportunistic Routing multiple paths are established and explored.