Delay-overhead trade-offs in mobile opportunistic network using TTL based restricted flooding

This paper deals with the delay-overhead trade-offs which can be achieved by restricting packet replication in mobile opportunistic networks, a special class of store-carry-forward network. In this regard we propose a TTL based Restricted Flooding Algorithm where each node is allowed to spread fixed number of message replicas at specified time intervals based on the time-to-live of the message. This overcomes high packet overhead ratio of unrestricted flooding while maintaining a comparable packet delivery ratio. By theoretically analyzing the scheme, we provide an upper bound of delivery delay and provide an estimate for number of message replicas which leads to minimum delay. Using theoretical framework we also show that the scheme is scalable and delay approaches a constant value when relative transmission overhead (i.e., transmissions/message) between restricted TTL scheme and the optimal scheme is kept constant. We discuss the performance of the proposed scheme with respect to delivery ratio, overhead ratio and delay and compare it with some of the well-known opportunistic routing algorithms like epidemic, spray-and-wait and prophet.