Spontaneous Collaboration in Mobile Peer-to-Peer Networks

The field of mobile Peer-to-Peer networks (MP2P) has various forms and currently there exists no coherent view on what is understood by it. The term mobile emphasizes that nodes/peers in the network are mobile, and therefore need to be equipped with some kind of wireless communication technology. Examples of nodes include pedestrians with mobile devices [284] or vehicles with wireless communication capabilities [632]. Since all mobile Peer-to-Peer networks construct an overlay over an existing wireless network, implementations range from MP2P over mobile ad hoc networks (MANETs) [156] to MP2P over cellular based networks [299, 298]. This chapter looks into a specific class of application for mobile Peer-toPeer networks. Here the Peer-to-Peer network is formed by humans carrying mobile devices, like PDAs or mobile phones, with ad hoc communication capabilities. All presented applications exploit the physical presence of a user to support digital or real-life collaboration among them. The integration of wireless communication technologies like Bluetooth or IEEE 802.11b WiFi into mobile devices makes this kind of mobile Peer-to-Peer networks feasible. As stated by Dave Winer, “The P in P2P is People” [624]; most of the Peer-to-Peer systems rely on the users’ will to contribute. This could be observed in the success of first generation file-sharing applications like Napster [438] or Gnutella [252]. The key issue of user contribution prevails even more in mobile Peerto-Peer networks, where in general anonymous users form the network with their personal devices. Resources on the device are typically limited. Especially battery power can be a problem. A user risks draining his battery by contributing its resources to other users. The device may also become unavailable for personal tasks, like accessing the calender or making phone calls. However user contribution may be stimulated by the usefulness of an application. Currently, we see the emergence of several mobile Peer-to-Peer applications, both as commercial products and in research, as described in Section 25.2. As stated above, all these applications make use of the physical presence