Opportunistic Networking Applications: From Theory to Practice

Teemu Kärkkäinen

Research output: ThesisDoctoral ThesisCollection of Articles


Modern smartphones are the primary gateways to information, entertainment, social networks, and private relationships for billions of people.They typically achieve this by connecting to centralized Internet services via fast wireless links. However, these smart devices have another, less used, set of communication capabilities:They can also talk directly over device-to-device communication technologies, and exchange content and messages without the need for the Internet. Message passing over these contacts creates an Opportunistic or a Delay-Tolerant Network. This form of networking is particularly useful in rural and remote areas that lack infrastructure, and in urban areas where the infrastructure has been overloaded by a crowd or disabled by a disaster. Even when infrastructure is available, it allows networking without relinquishing control and privacy to a centralized service. In this dissertation, we contribute to advancing the availability and capability of opportunistic networking. We advance the availability by improving the opportunities for creating opportunistic contacts for smartphones, and the capability by designing advanced mechanisms for both content and computation interactions. For connectivity, we measure to what extent existing public Wi-Fi access points allow direct device-to-device communications. We then introduce mechanisms to help scale device-to-device communications in access points with many clients. As an alternative to using existing infrastructure, we introduce the Liberouter neighborhood networking system based on cheap stand alone opportunistic routers. On top of this basic connectivity, we design more advanced content access mechanisms to ease the development of opportunistic networking applications. In particular, we design a request/response mechanism for accessing content, particularly websites, that reside on servers outside the opportunistic network. We also design a query/response mechanism to search for content in other nearby devices. Finally, we present mechanisms for shared content editing, e.g., wikis, in opportunistic networks. We also introduce mechanisms to support opportunistic computations. First, we enable interactive web applications in the Liberouter network by attaching custom computations to the content messages. Second, we design a framework for the Liberouters for the opportunistic composition of general distributed services. Together, these contributions help advance the technical basis for smartphone-based opportunistic networking applications.
Translated title of the contributionOpportunististen tietoverkkojen sovellukset: teoriasta käytäntöön
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Ott, Jörg, Supervising Professor
  • Hyytiä, Esa, Thesis Advisor
Print ISBNs978-952-64-0321-2
Electronic ISBNs978-952-64-0322-9
Publication statusPublished - 2021
MoE publication typeG5 Doctoral dissertation (article)


  • opportunistic networking
  • delay-tolerant networking


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