Peer-to-Peer Solutions for Cellular Networks Andreas Berl and Hermann de Meer Computer Networks and Communications University of Passau, Germany Email: {berl,demeer}@uni-passau.de Tobias Hoßfeld Department of Distributed Systems University of W¨ urzburg, Germany Email: hossfeld@informatik.uni-wuerzburg.de Abstract The participation of stationary computers with high- bandwidth links in peer-to-peer content-distribution networks is highly popular. Mobile devices (e.g. cell phones), however, could not yet be launched into the field to a satisfactory extent. This paper discusses mobile peer-to-peer approaches that cover this issue and compares two promising approaches in detail. The first approach supports mobile devices by adding new infrastructure elements to the mobile network opera- tor’s domain. In the second approach, voluntary peers provide support for mobile devices. Both approaches are able to foster the integration of mobile devices into peer-to-peer networks with a large user community. 1. Introduction Peer-to-peer (P2P) content-distribution applications are widely spread on stationary computers in fixed networks today. But also mobile devices (MDs) in cellular radio networks, e.g. phones or personal digital assistants, are potential candidates for participating in these popular P2P networks. Their integration into pop- ular P2P content-distribution networks (CDNs) with large user communities is a special instance of the mobile peer-to-peer (mobile P2P) research field [1] . Although current MDs mostly have enough hard- ware resources to join such P2P networks, they are barely able to benefit from them. Their participation together with a large number of stationary comput- ers with high-bandwidth links, increases heterogeneity within P2P networks, which causes performance prob- lems, especially for MDs, cf. [2]. In contrast to this heterogeneity, P2P systems apply homogeneous logical structures (the overlay), in which computers and links are considered to be equal, having similar properties and capabilities. Several mobile P2P approaches have been sug- gested, focussing on cellular radio networks. Although some of them might be applicable to popular CDNs, MDs are still not widely integrated in them. These approaches are categorized and their shortcomings are discussed in Section 2. In addition, two approaches towards an integration of mobile peers into popular P2P-based CDNs are presented in detail and compared to each other. First, Section 3 presents a mobile P2P architecture, in which the Mobile Network Operator (MNO) supports MDs in his domain by integrating additional infrastructure elements [3]. The MNO aims at improving the cus- tomer’s experience with the P2P-based CDN, while maintaining control over the network, e.g., in order to reduce expensive inter-domain traffic. Second, Sec- tion 4 describes a mobile P2P architecture, in which MDs are supported by specialized peers, enabling them to efficiently profit from the P2P network [4]. MDs provide mobile services in return to compensate for this support. Section 5 compares the two approaches and Section 6 concludes this paper. 2. Mobile P2P Solutions Mobile P2P approaches that focus on cellular ra- dio networks are partitioned in three categories with respect to the support they provide to MDs: 1) no additional support, 2) support from the P2P protocol, and 3) other support not being part of the P2P protocol. No support: Solutions of this category are re- shaping P2P client software to the requirements of MDs, considering the MDs limitations, whereas the P2P protocol remains unchanged. MDs join P2P networks as ordinary peers without getting further support. In this paper, this approach is called the straight-forward approach or no support solution. Symella (http://symella.aut.bme.hu), e.g., is such a P2P client for the Gnutella [5] P2P file-sharing net- Copyright and Reference Information: This material (preprint, accepted manuscript, or other author-distributable version) is provided to ensure timely dissemination of scholarly work. Copyright and all rights therein are retained by the author(s) and/or other copyright holders. All persons copying this work are expected to adhere to the terms and constraints invoked by these copyrights. This work is for personal use only and may not be redistributed without the explicit permission of the copyright holder. The definite version of this work is published as [·] Andreas Berl, Hermann De Meer and Tobias Hossfeld. P2P solutions for cellular networks. In Proc. of the 1st Int’l Conf. on Advances in P2P Systems (AP2PS 2009), pages 54–59. IEEE Computer Society, 2009. See http://www.net.fim.uni- passau.de/papers/Berl2009c for full reference details (BibTeX, XML).