ABSTRACT
CONTENTS 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 3.2 Mobility-Induced Link-Level Metrics and Network Performance . . . . 73
3.2.1 Mathematical Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 3.2.2 The Status Quo for Mobility-Induced Link-Level Dynamics 74
3.3 Impact of User Availability on Link-Level Dynamics: Model and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.3.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.3.2 User Availability Comes into Picture . . . . . . . . . . . . . . . . . . . . . . . 80 3.3.3 Analysis of Link-Level Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.3.3.1 Transfer-Time Distribution and Mean Inter-transfer Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.3.3.2 Inter-transfer Time Distribution . . . . . . . . . . . . . . . . . 83
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.5 Discussion and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.1 Introduction Opportunistic networks, a.k.a., delay-or disruption-tolerant networks, have emerged as one of the most promising evolutions of mobile ad hoc networks, and are designed to operate without the need of infrastructure support and in the presence of frequent disruptions in link connectivity. In these networks, mobile nodes exploit node mobility and opportunistic contacts (based on their geographical proximity) for communications, while coping with such intermittent connectivity. The so-called store-carry-and-forward paradigm is, thus, used as a means of forwarding and routing in opportunistic networks: mobile nodes can carry messages, and copy and/or relay them to other nodes when they come into contact, thereby rendering messages eventually delivered to their destinations, even if end-to-end paths never exist [46]. In other words, direct device-to-device communications based upon opportunistic contacts and the cooperation of participating nodes (as relay nodes) enable network-wide communications.
