How does user heterogeneity affect performance of P2P caching?: Evolutionary game theoretic approach

Ubiquitous information societies enables us to freely obtain information anytime and anywhere. Beyond this concept, achievement of ambient information societies has been expected in recent years, in which we can retrieve desired information in accordance with current conditions of surrounding environments. In this paper, we focus on Peer-to-Peer (P2P) file sharing systems as an example of such ambient information sharing systems. We try to figure out the system performance when all users behave selfishly and autonomously according to their surrounding situations. In P2P file sharing systems, file availability is improved by users cooperatively caching and sharing files. However, many users may hesitate to cache files cooperatively due to the cost for caching, such as storage consumption, processing load, and bandwidth consumption. In such a case, unpopular files are likely to disappear from the system. In this paper, we reveal how the selfish user behavior affects the system performance using evolutionary game theoretic approach. Specifically, we focus on situations where users are heterogeneous in terms of aggressiveness in cooperative caching. Analytical results show that the user heterogeneity contributes to the stability of file availability.