Push-to-Talk in IMS Mobile Environment

The IP multimedia subsystem (IMS), originally designed by 3GPP and later updated by 3GPP, 3GPP2 and TISPAN, presents itself as an architectural framework that allows the convergence of the Internet, wireless and wireline networks and a global platform for the delivery of IP multimedia applications in next generation networks (NGN). One of the most used services to test IMS capabilities is push-to-talk (PTT). This service follows the IMS specifications and has motivated standardization work by the Open Mobile Alliance to assure interoperability between different operators. This paper describes a PTT over IMS solution designed with a talk burst control protocol based on SIP messages for call session control. The implementation was deployed and tested both with high-bandwidth LAN and CDMA2000 wireless network, demonstrating that IMS is a powerful and flexible architecture allowing the quick and easy development of multimedia applications, like PTT, for convergent networks.