Node Density-Based Adaptive Spray and Focus Routing in Opportunistic Networks

Message delivery is one of the challenging issues in opportunistic networks because of the short-lived connectivity environment. To deal with this issue, replication-based routing protocols inject a specific number of multiple message copies into the network to achieve the tradeoff between the delivery probability and overhead. However, in most of the current copy-limited routing algorithms, message copies would be premature to be distributed. In the case of high node density, a large number of message copies are limited to the small local area, which causes long delay and low delivery ratio. To address this problem, a node Density-based Adaptive Spray and Focus (DASF) routing algorithm is proposed in this paper. By estimating the node density of the current location, DASF could control the total number of message copies for allocation. Then it decides the proportion of message copies between encountered nodes according to the level of node activity. Simulation results show that the proposed DASF routing algorithm can improve delivery ratio and reduce the average message transmission delay when node density increases.