Spontaneous Cooperation in Future Wireless Networks ?

1. Spontaneous Cooperation in Future Wireless Networks ? Márk Félegyházi Laboratory for Computer Communications and Applications (LCA) EPFL, Switzerland

2. Future Wireless Networks • Emerging networks • Cellular networks in a shared spectrum • Hybrid ad hoc networks (also called “Multi-hop cellular networks”) • Small operators, community networks • Mesh networks • Cognitive radio communication • “Autonomous” ad hoc networks • Vehicular networks • Sensor and RFID networks • Emerging properties • Centralized → Distributed • More sophisticated user devices • Self(ish)-organization

3. Spontaneous Cooperation in Emerging Networks? Channel allocation (spectrum allocation) Packet forwarding Channel access Power control … Cellular networks in a shared spectrum Hybrid ad hoc networks Small op., comm. NWs Mesh networks Cognitive radio communication Autonomous ad hoc NWs Vehicular networks Sensor networks

4. Game Theory: an Appropriate Tool Study rational behavior in wireless networks ↓ Design enforcement mechanisms (if necessary)

5. Problems We Studied Channel allocation (spectrum allocation) Packet forwarding Channel access Power control … Cellular networks in a shared spectrum Hybrid ad hoc networks Small op., comm. NWs Mesh networks Cognitive radio communication Autonomous ad hoc NWs Vehicular networks Sensor networks

6. Packet forwarding in ad hoc networks Dependency: the benefit of each source is dependent on the behavior of its forwarders dependency loop Theorem 3 (simplified): Assuming that node i is a forwarder, its behavior will be cooperative only if it has a dependency loop with each of its sources Corollary 2: If Theorem 3 holds for every node, it is a Nash-equilibrium. A B BUT Example in which Corollary 2 holds: Simulation results → in general, Corollary 2 does not hold C

7. Cellular Networks in a Shared Spectrum • Game G = (Players, Strategy, Utility function) • Players: operators • Strategy: radio range of base stations • Utility: useful coverage of their pilot signal: Static game – Pareto-optimal Nash equilibria • freely roaming users • power control of the pilot signal • users attach to the base station with the best pilot signal: Repeated game – A Nash equilibrium based on RMIN is enforceable using punishments where the channel gain:

8. References • Tutorials on game theory: • A. Mackenzie, L. Da Silva, and W. Tranter (Editor), Game Theory for Wireless Engineers,Morgan & Claypool Publishers, 2006 • M. Félegyházi and J.-P. Hubaux, Game Theory for Wireless Networks: A Tutorial, LCA-REPORT-2006-002, April 2006 • Packet forwarding in ad hoc networks: • V. Srinivasan, P. Nuggehalli, C. Chiasserini, and R. Rao, Cooperation in Wireless Networks, IEEE Transactions on Wireless Communications 2005 • M. Félegyházi, J. P. Hubaux, and L. Buttyán, Nash Equilibria of Packet Forwarding Strategies in Wireless Ad Hoc Networks, IEEE Transactions on Mobile Computing 2006 • Cellular networks in a shared spectrum: • M. Félegyházi and J. P. Hubaux, Wireless Operators in a Shared Spectrum, Infocom 2006 • Textbook in preparation: • L. Buttyán and J. P. Hubaux, Security and Cooperation in Wireless Networks, Cambridge University Press, 2007 • …

9. Graduate Textbook L. Buttyán and J. P. Hubaux “Security and Cooperation in Wireless Networks” Cambridge University Press, 2007 V1.0 full text available at: http://secowinet.epfl.ch (430 pages) • Part I: Existing and upcoming wireless networks • Part II: Thwarting malicious behavior • Part III: Thwarting selfish behavior • Appendix A: Introduction to security and cryptographic functions • Appendix B: Tutorial on game theory for wireless networks

10. Conclusion • Cooperation is usually assumed → selfishness can degrade network performance • Selfish or malicious ? → different mechanisms • In general, incentives for cooperation are needed • Links of our group: • Speaker: http://people.epfl.ch/mark.felegyhazi • Textbook: http://secowinet.epfl.ch • Articles: http://winet-coop.epfl.ch