Archived Technical Report

K. N. Sridhar and Mun Choon Chan, "Link Lifetimes: Distribution, Estimation and Application in Mobile Ad hoc Networks," Technical Report, Center for Internet Research, June 2008.

Lifetime of a link defines the amount of time the link is available for transmission. In this work, we begin with associating a statistical parametric model for link lifetime distribution for commonly used mobility patterns. The study reveals interesting properties about link lifetimes, including findings showing that lifetimes of the mobility patterns studied are of wear-out type, rather than random failure. Next, we propose a heuristics based link lifetime estimation process that exploits knowledge of the associated mobility pattern and show that the estimation performs well under diverse operating conditions. Finally, we present an application of link lifetime. In this application, link lifetime is used as an indicator of end-to-end channel-quality to carry out packet scheduling decisions.

Binbin Chen and Mun Choon Chgan, “MobiCent: a Credit-Based Incentive System for Disruption Tolerant Network,” Technical Report, Center for Internet Research, July 2009.

When Disruption Tolerant Network (DTN) is used in commercial environments, incentive mechanism should be employed to encourage cooperation among selfish mobile users. Key challenges in the design of an incentive scheme for DTN are that disconnections among nodes are the norm rather than exception and network topology is time varying. Thus, it is difficult to detect selfish actions that can be launched by mobile users or to pre-determine the routing path to be used. In this paper, we propose MobiCent, a credit-based incentive system for DTN. While MobiCent allows the underlying routing protocol to discover the most efficient paths, it is also incentive compatible. Therefore, using MobiCent, rational nodes will not purposely waste transfer opportunity or cheat by creating non-existing contacts to increase their rewards. MobiCent also provides different payment mechanisms to cater to client that wants to minimize either payment or data delivery delay.

Binbin Chen and Mun Choon Chan, “Incentive-compatible Resource Allocation in Overlapping Heterogeneous Wireless Networks,” Technical Report, Center for Internet Research, July 2009.

This paper considers the coordinated radio resource allocation problem for users which are simultaneously covered by multiple overlapping heterogeneous wireless networks. As the resource allocation decision depends on the channel measurement and feedback from users, inefficiency and instability arise if a selfish user can manipulate its measured channel state to increase its gain from network. Our contribution in this paper is the introduction of incentive compatibility as an addition criterion in the design of a resource allocation scheme. We formulate the multi-cell resource allocation game to capture the strategic interactions among users. A resource allocation scheme is incentive compatible if each user’s dominant strategy under the resulted game is to honestly report its channel state. We consider both multi-association setting, where a MS is allowed to simultaneously associate with multiple BSs, and single-association setting, where a MS is only associated with one BS. We show that for multi-association setting, a natural generalization of proportional fair allocation is incentive compatible. In contrast, the optimal solution using the same fairness criterion under single-association is not incentive compatible. In order to exploit the benefit of single-association, we propose an allocation scheme based on selfish load balancing. We show that such a scheme always converges to a Nash equilibrium, and achieves performance close to the optimal single-association allocation.