Delivery ratio- and buffered time-constrained: Multicasting for Delay Tolerant Networks

Almost all multicast routing algorithms for Delay Tolerant Networks (DTNs) mainly focus on improving routing performance, but hardly consider the constraints in actual DTN applications. In this paper, we investigate the constrained multicasting problems in social network scenarios. A pattern of constrained multicasting is defined, and then based on the node mobility in social network scenarios that the pair-wise inter-contact time is exponentially distributed, we propose a Delivery Ratio- and Buffered Time-Constrained Multicast routing algorithm, named as DBCM. DBCM considers the delivery predictability as utility value within the maximum buffered time, and makes routing decisions based on the utilities of current neighbors. To utilize contact more effectively, an enhanced scheme of DBCM, called E_DBCM, is introduced. E_DBCM can increase message delivery ratio without inducing additional overhead. The performance of DBCM is analyzed theoretically in terms of message delivery ratio, average number of hops and end-to-end delay. We also develop the RWP mobility model, and propose a social mobility based version (SM_RWP). Pair-wise inter-contact time in SM_RWP is proven to follow exponential distribution. Simulation results show that DBCM and E_DBCM outperform the most of the existing multicasting algorithms on delivery ratio and routing overhead.