A new reliable transport scheme in Delay Tolerant Networks based on acknowledgments and random linear coding

We propose a new reliable transport scheme for Delay Tolerant Networks (DTNs) based on the use of acknowledgments (ACKs) as well as coding. We, specifically, develop a fluid-limit model to derive expressions for the delay performance of the proposed reliable transport scheme and derive the optimal setting of the parameters which minimize the file transfer time. Our results yield optimal values for the number of outstanding random linear combinations to be sent before time-out as well as the optimal value of the time-out itself, which, in turn, minimize the file transfer time.

I. Introduction

Delay Tolerant Networks (DTNs) are Mobile Ad Hoc NETworks (MANETs) in which the number of mobile nodes per unit area is typically very low which makes the connectivity between the nodes intermittent. In a DTN environment, in the absence of connectivity, a source node has to rely on the mobility of other nodes which act as relays, and takes advantage of the transmission opportunities which occur when the mobile relays come into contact. Hence, the transfer of data in DTNs is very much dependent on the mobility of the nodes and the packet replication method. Such forwarding strategy is commonly known as opportunistic routing [1], [2].