Closed P2P system for PVR-based file sharing

Most data placement schemes of P2P systems are based on open systems where a node can access any data in the system once the node joins the system, which is not suitable for PVR-based file sharing, because PVR is a private device. This paper suggests a closed P2P model where a node is connected only with some specific nodes and data are shared only within those nodes. In this model, since shared files usually contain large multimedia data, the data placement scheme employed should maximize the space available to each node by increasing the degree of sharing and by reducing redundancy in data placement. In this paper, we prove that the problem to maximize the space is NP-hard and suggest several heuristic approaches that can be realized on a peer-to-peer architecture. Performance problems of the above algorithms are explored through simulation studies.