The use of Social network is becoming gradually more popular on mobile devices. The important component of a social network application is a mobile presence service because it maintains each mobile user's presence information, such as the current status (online/offline), GPS location and network address, and also updates the user's online friends with the information repeatedly. If presence updates occur frequently, the enormous number of messages distributed by presence servers may lead to a scalability problem in a large-scale mobile presence service. We propose an efficient and scalable server architecture, called PresenceCloud, to address the problem, which enables mobile presence services to support large-scale social network applications. PresenceCloud searches for the presence of his/her friends and notifies them of his/her arrival when a mobile user joins a network. For efficient presence searching presenceCloud categorizes presence servers into a quorum-based server-to-server design. Directed search algorithm and a one-hop caching strategy to achieve small constant search latency is also controls by it. The performance of PresenceCloud we scrutinize in terms of the search cost and search satisfaction level. The search cost is characterized as the total number of messages generated by the presence server when a user arrives; and search approval level is defined as the time it takes to search for the arriving user's friend list. The results of simulations demonstrate that PresenceCloud achieves performance gains in the search cost without compromising search satisfaction.
Social networks, mobile presence services, distributed presence servers, cloud computing
