POC
Push to talk Over Cellular
POC which is also termed PTT (Push To Talk) uses the GPRS network to send packetized speech between participants of a POC session. The process as far as the user is concerned can be likened to CB Radio in which users share a communication channel, by pressing the button to talk, and then releasing it to allow other participants to speak. PoC is also available as an IMS managed service, with PoC sessions established using SIP. In this case, the IP-CAN is not necessarily GPRS.