在無線隨意網路中，節點經由中介節點的轉送來與其他的節點做通訊，而這些中介節點彼此間必須共同合作才能使得網路的傳輸更加可靠。然而網路中可能存在著一些自私或惡意的節點，這些自私的節點可能為了節省電池能源而不願意提供服務或轉送訊息；而惡意的節點可能蓄意破壞網路或不願遵守協定所制定的規則。有一些信譽系統及提供鼓勵的機制被提出來解決這些問題，並促使在無線隨意網路中的各個節點都能彼此間共同合作。
在本論文中，我們提出了一個以鼓勵為基礎的信譽系統來鼓勵這些自私的節點能夠在封包的轉送上共同合作，並且運用信譽的機制來防止節點的惡意行為。這是一個完全自我組織管理的系統，每個提供服務的節點所獲得的報酬以及每個使用服務的節點所支付的費用是以賽局理論的觀點來設計，並且也考慮到各個節點合作機率的問題所造成的影響。同時我們也將整個系統的付費機制設計成一個訊息轉送的遊戲，並且證明了在這個系統中，對每個節點來說合作會是最佳的策略。因此透過這些機制，每個節點都樂意提供訊息轉送的服務來增加自己的報酬。最後，透過軟體模擬的結果，顯示出在一般的情況下，在這個系統中節點傳送訊息的成功機率很高，每個結點都願意彼此合作來轉送訊息，並且配合信譽機制也同時提高了網路的效能。

In mobile ad hoc networks, nodes communicate with others usually using intermediate nodes as relays; and they are expected to cooperate to make the networks reliably. Several reputation systems and incentive mechanisms have been proposed for mobile ad hoc networks in order to stimulate cooperation among the participating nodes. In this thesis, we propose an incentive-based reputation system to motivate the selfish nodes to cooperate in packet forwarding, and apply a simple reputation scheme to encourage the trustworthy behaviors; this system is fully self-organized and the reward of each node is determined from a game theoretical viewpoint. We also take the cooperating probability of each node in the network into account, and prove that cooperating is the optimal strategy for each node in our system. The results of performance evaluation show that the selfish nodes can cooperate with each other in the general situations.

[1] S. Marti, T. Giuli, K. Lai, and M. Baker, “Mitigating Routing Misbehavior in Mobile Ad Hoc Networks,” in Proceedings of The Sixth International Conference on Mobile Computing and Networking 2000, Boston, MA, Aug. 2000.
[2] S. Buchegger and J.-Y Le Boudec, “Performance Analysis of the CONFIDANT Protocol: Cooperation of Nodes - Fairness in Dynamic Ad-Hoc Networks,” in Proceedings of IEEE/ACM Workshop on Mobile Ad Hoc Networking and Computing (MobiHOC). IEEE, June 2002.
[3] S. Buchegger and J.-Y Le Boudec. “The Effect of Rumor Spreading in Reputation Systems in Mobile Ad-hoc Networks,“ in Proceedings of Modeling and Optimization in Mobile, Ad Hoc and Wireless networks (WiOpt’03), INRAI Sofia-Antipolis, France, Mar. 2003.
[4] P. Michiardi and R. Molva, “CORE: A Cooperative Reputation Mechanism to enforce node cooperation in Mobile Ad hoc Network,” in Communications and Multimedia Security Conference (CMS) 2002.
[5] P. Michiardi, and R. Molva, “Simulation-based analysis of security exposures in mobile ad hoc networks,” in European, Wireless 2002 Conference, Florence, Italy, Feb. 2002.
[6] P. W. Yau, C. J. Mitchell, “Reputation Methods for Routing Security for Mobile Ad Hoc Networks,” Joint IST Workshop on Mobile Future and Symposium on Trends in Communications (SympoTIC’03), Pages:130 – 137, Bratislava, Slovakia, Oct. 2003.
[7] Qi He, Oliver D. Wu and Pradeep Khosla, “SORI: A Secure and Objective Reputation-based Incentive Scheme for Ad-hoc Networks,” in Proceedings of IEEE Wireless Communications and Networking Conference (WCNC) 2004, Pages:825 – 830, Atlanta, Georgia, March 2004.
[8] A. Spyropoulos and C. Raghavendra, “Energy Efficient Communications in Ad Hoc Networks Using Directional Antennas,” in Proceedings of IEEE INFOCOM ’02, New York, NY, June 2002.
[9] J. E. Wieselthier, G. Nguyen, and A. Ephremides, “Energy-limited Wireless Networking with Directional Antennas: The case of Session-based Multicasting,” in Proceedings of IEEE INFOCOM ’02, New York, NY, June 2002.
[10] L. Buttyan and J. P. Hubaux, “Nuglets: A Virtual Currency to Stimulate Cooperation in Self-Organized Mobile Ad-Hoc Networks”. Technical Report DSC/2001/001, Swiss Federal Institute of Technology, Lausanne, Switzerland, Jan. 2001.
[11] L. Buttyan and J. P. Hubaux, “Enforcing Service Availability in Mobile Ad-Hoc WANs,” in IEEE/ACM Workshop on Mobile Ad Hoc Networking and Computing (MobiHOC), Boston, MA, Aug. 2000.
[12] L. Buttyan and J. P. Hubaux, “Stimulating Cooperation in Self-Organizing Mobile Ad Hoc Networks,” ACM Journal for Mobile Networks (MONET), special issue on Mobile Ad Hoc Networks, Oct. 2003.
[13] S. Zhong, J. Chen and Y.R. Yang, “Sprite: A Simple, Cheat-Proof, Credit-based System for Mobile Ad-Hoc Networks,” in Proceedings of IEEE INFOCOM ’03, San Francisco, CA, Apr. 2003.
[14] V. Srinivasan, P. Nuggehalli, Carla F. Chiasserini and Ramesh R. Rao, “Cooperation in Wireless Ad Hoc Networks”, in Proceedings of IEEE INFOCOM ’03, San Francisco, CA, Apr. 2003.
[15] M. Felegyhazi, L. Buttyan, and J.P. Hubaux, “Equilibrium Analysis of Packet Forwarding Strategies in Wireless Ad Hoc Networks – the Static Case,” in Proceedings of International Conference on personal Wireless Communications (PCW’03), Venice, Italy, Sept. 2003.
[16] A. Urpi, M. Bonuccelli, and S. Giordano, “Modeling Cooperation in Mobile Ad Hoc Networks: a Formal Description of Selfishness,” in Proceedings of Modeling and Optimization in Mobile, Ad Hoc and Wireless networks (WiOpt’03), Sophia-Antipolis, France, Mar. 2003.
[17] P. Michiardi and R. Molva, “A Game Theoretical Approach to Evaluate Cooperation Enforcement Mechanisms in Mobile Ad Hoc Networks,” in Proceedings of Modeling and Optimization in Mobile, Ad Hoc and Wireless networks (WiOpt’03), Sophia-Antipolis, France, Mar. 2003.
[18] J. Crowcroft, R. Gibbens, F. Kelly, and S. Ostring, “Modelling Incentives for Collaboration in Mobile Ad Hoc Networks,” in Proceedings of Modeling and Optimization in Mobile, Ad Hoc and Wireless networks (WiOpt’03), Sophia-Antipolis, France, Mar. 2003.
[19] O. Ileri, S.-C. Mau, N. Mandayam, “Pricing for Enabling Forwarding in Self-Configuring Ad Hoc Networks,” in Proceedings of IEEE Wireless Communications and Networking Conference (WCNC) 2004, Atlanta, Georgia, March 2004.