Downlink Traffic Modeling and Analysis for Push to Talk over Cellular

This paper presents the downlink traffic pattern and analytical evaluation for Push-to-Talk over Cellular (PoC), which is a half duplex voice over IP (VoIP) service using IP capable Network. The behavior of user to form group and the nature of conversation within the group members are modeled and analyzed by simulation. Group session generation procedure is modeled by Binomial model while the floor control traffic is modeled as Poisson model and voice traffic has an ON-OFF traffic model. The Session Initiation Protocol (SIP) signaling is considered without using any compression algorithm and the GPRS and PoC voice traffic are considered at the packet level. Both PoC signaling and voice traffic share the GSM traffic channel with the GPRS traffic following FCFS queuing model and Fair Share Round Robin scheduling algorithm. The effect on PoC signaling traffic due to different group formation mode, user answering mode and session mode and effect of group size on PoC voice traffic are investigated and analyzed in this paper. We have developed an event driven simulator using Java programming language to simulate PoC traffic.