A hierarchical social network-based P2P SIP system for mobile environments

P2P SIP (peer to peer session initiation protocol) systems have emerged as a new trend in multimedia realm due to their abilities to overcome the shortcomings of conventional SIP systems. Most of P2P SIP systems were implemented using Chord, a Distributed Hash Table (DHT) based routing algorithm which can provide scalability and reliability. Previous studies on P2P SIP systems did not address node heterogeneity, location information and mobility issues all together. For node heterogeneity, nodes with different capabilities (processing power, storage and bandwidth) should be treated suitably. For location information, the signaling latency is correlated with the distance between end users. This will influence call setup latency greatly. As to mobility, the node churn property will involve additional messages to maintain a stable DHT-based network and increases call setup latency. To conquer these problems, we propose a hierarchical social network-based P2P SIP system. The social network property can increase routing efficiency when calling friends. In addition, the proposed hybrid (structured/ unstructured) overlay is more resilient to cope with node churn. Simulation results show that our approach can improve 32% call setup latency with non-buddies and reduce 63% maintenance cost in comparison with the conventional Chord-based approach. In addition, we improve lookup efficiency from O(logN) to O(1) when making calls with buddies, where N is the number of nodes in a DHT-based network.