A Buffer Management Strategy Based on Power-Law Distributed Contacts in Delay Tolerant Networks

Abstract

In Delay Tolerant Networks (DTNs) with resource constraints such as short contact durations and small buffers, message scheduling and drop prioritization is a critical issue as it affects the routing performance. Current solutions mainly focus on devising buffer management strategies by assuming that the contact rates between mobile nodes are exponentially distributed. While this assumption is suitable for vehicular mobility scenarios such as taxicabs in a city, it is often invalid for mobility traces that feature human-assisted devices. Recent studies have shown that human mobility traces follow a truncated power-law distribution. In this paper, we propose a new buffer management strategy based on power-law distributed contacts. The main objective is to minimize the average message delivery delay in DTN networks with resource constraints and heterogeneous node mobility. We focus on two key issues: (1) in which order should messages be replicated when contact duration and forwarding bandwidth are limited, and (2) which messages should be dropped first when the buffer is full. We develop a utility function using global network information to compute per-packet average delay utility. Messages are then scheduled and dropped according to their utility values. Extensive simulation results based on real-life human mobility traces show that our proposed scheme can deliver messages in up to 27% less time than existing schemes, while still achieving a high delivery ratio.