A Study of Presence Services in SIP-Based Group Communication Systems

摘要

As the Presence Service provides users with dynamic information such as status and availability of their contacts increases the likelihood for success of the user's communications, and enhances user satisfaction. Currently the Presence Service is used importantly in VoIP and Instant Messaging Service. However, in the systems that a real-time property is required, presence service should be provided limitedly and efficiently because it is in the trade-off relation with a real-time property. In this paper, we propose more effective Presence Service in the Group Communication System based on SIP. As the Presence Service of in this paper extracts the presence information from the normal SIP messages and sends minimal changed presence information to previously defined watchers instead of the OMA defined SIMPLE framework which consists of complex presence messages such as REGISTER, SUBSCRIBE, PUBLISH and NOTIFY it can be provided more efficiently in the Group Communication System.