Interaction predictability of opportunistic networks in academic environments

Abstract

ABSTRACTThe ubiquitousness of mobile devices in recent years has led to an ever‐growing interest in mobile networks. One such example is represented by opportunistic networks, which are composed of mobile devices that interact in a store‐carry‐and‐forward fashion. A mobile node stores data and carries it around; when it encounters another node, it may decide to forward the data if the encountered node is the destination or has a better chance of bringing the data closer to the destination. If the encountered node is likely to have a contact with the destination sooner than the data carrier, the data should be forwarded, in order for it to reach its destination with a lower delivery latency. Because nodes in opportunistic networks are carried by humans, their mobility plays a very important role in the behaviour of the network. Therefore, predicting a node's interactions and mobility patterns is paramount to the implementation of efficient routing algorithms. Thus, in this paper we present a mobile interaction trace collected at the University POLITEHNICA of Bucharest in the spring of 2012 and analyse it in terms of the predictability of encounters and contact durations. We show that there is a regular pattern in the contact history of a node and we prove that by modelling the time series as a Poisson distribution (with the number of contacts being the Poisson events in a fixed one‐hour interval), we can efficiently predict the number of contacts per time unit in the future. These assumptions are demonstrated both on the trace presented here, as well as on a trace recorded in a different environment, showing that predictability doesn't happen only in strict and controlled situations. Moreover, we analyse the predictability of an opportunistic node's sightings of wireless access points, which can help us discover a user's patterns and behaviour. Copyright © 2013 John Wiley & Sons, Ltd.