Cooperative Content Distribution Networks in Cellular Networks
We evaluate the performance of a P2P-based content distribution system in heterogeneous, wireless networks. The mobile users coordinate each other with cooperation strategies enabled by the multi-source download mechanism, as in eDonkey or BitTorrent. Due to the mobility, vertical handovers between different wireless access technologies are required which may result in transmission delays and IP address changes of the switching peer. Hence, connections among users have to be reestablished and downloading users are requeued at a providing peer<92>s waiting queue. In detail, we investigate a) the impact of requeueing with each VHO as well as the use of mechanisms that preserve the IP address and connections beyond VHOs, like MobileIP; b) the abrupt change of the available bandwidth, e.g., from a fast WLAN connection to a rather slow UMTS connection; c) the impact of user behavior, i.e. seeders and leechers. As a result, we develop different cooperation strategies to increase the efficiency and the robustness of the system while minimizing signaling traffic and guaranteeing fairness among users.
Supporting Mobility by P2P
Vertical handovers are expected to be a key feature in Beyond 3G (B3G) networks. We investigate the application of structured P2P overlay networks for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points for mobile entities and to retrieve rapidly the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability. In addition, this approach is applied for the configuration and management of radio access nodes in Beyond 3G (B3G) networks We compare the efficiency and the scalability of Pastry, CAN, and Kademlia and modify the protocols to optimize them w.r.t. these particular tasks.