A message ferrying scheme with differentiated services

Routing in partitioned ad-hoc networks is a challenging problem since end-to-end connectivity may not exist. A message ferrying (MF) (W. Zhao and M.H. Ammar, 2003) scheme has been proposed recently for non-real-time applications where certain mobile nodes referred to as message ferries are designated to collect and deliver packets. In R. Viswanathan et al. (2005), we have investigated a message ferrying scheme that allows urgent messages with more stringent delay requirement to be delivered earlier than regular messages. In this paper, we analyze a system where these two types of messages arrive according to an arrival distribution and that the buffer sizes at the ferry and the nodes are limited. We also assume that the nodes move and that the urgent/regular messages have different delivery deadlines. We design an elliptical zone forwarding (EZF) scheme for the ferry route. Then, we study how three buffer allocation schemes affect the fraction of delivered urgent messages that meet the deadlines as well as the dropping rates of urgent and regular messages due to buffer contention when used together with the EZF scheme. Our results indicate that the soft-partitioning scheme allows more urgent messages to be delivered while keeping the drop rate of regular messages low. Next, we compared the system performance achieved by the EZF scheme with the ferry initiated message ferry with nearest neighbor scheme presented in W. Zhao et al. (2004) assuming the FIFO scheme is used for the buffer allocation. Our simulation studies show that the EZF scheme we design achieves better performance than the FFM-NN scheme. The EZF routing scheme combined with the buffer allocation scheme can be used to intelligently disseminate information in military networks