Impact of Human Mobility on the Design of Opportunistic Forwarding Algorithms

TLDR

The inter‑contact time between human‑carried devices follows a heavy‑tailed distribution, contradicting the exponential decay assumed by most mobility models. In this paper, we study how this new characteristic of human mobility impacts a class of previously proposed forwarding algorithms. We use a simplified model based on renewal theory to study how the distribution parameters affect the delay performance of these algorithms. The heavy‑tailed inter‑contact time was confirmed across six datasets, and we recommend design guidelines for opportunistic forwarding algorithms based on this insight.

Abstract

Studying transfer opportunities between wireless devices carried by humans, we observe that the distribution of the inter-contact time, that is the time gap separating two contacts of the same pair of devices, exhibits a heavy tail such as one of a power law, over a large range of value. This observation is confirmed on six distinct experimental data sets. It is at odds with the exponential decay implied by most mobility models. In this paper, we study how this new characteristic of human mobility impacts a class of previously proposed forwarding algorithms. We use a simplified model based on the renewal theory to study how the parameters of the distribution impact the delay performance of these algorithms. We make recommendation for the design of well founded opportunistic forwarding algorithms, in the context of human carried devices.