Impact of node density and TTL in vehicular delay tolerant networks: performance comparison of different routing protocols

In this work, we evaluate the performance of different routing protocols in vehicular delay tolerant networks (VDTNs). We study the impact of vehicles density and TTL on the network performance. The simulations are conducted with the opportunistic network environment (ONE) simulator. The performance is analysed using delivery probability, overhead ratio, average latency and average number of hops metrics. The simulation results show that the increase of node density improves the network performance. In dense network scenario, the performance of epidemic and maxprop routing protocols is better because the number of opportunistic contacts between nodes increases. For spray and wait, the performance is not improved since it uses a maximum of two hops to deliver bundles. Hence, in dense networks, a bundle may have a significant delay because it can only be delivered when a relay or source node have an opportunistic contact with the destination. The increase of ttl from 30 to 120 min does not improve the performance of three routing protocols in both scenarios. Multiple-copy protocols perform better in terms of delivery probability compared with single-copy protocol. The single-copy protocol uses the highest average number of hops and higher average latency compared with multiple-copy protocols.