A method and apparatus are provided for transmitting a Session Initiation Protocol message by a User Equipment in {TAIL ~ an idle mode} in {HEAD ~ an Internet Protocol Multimedia Subsystem system} 
A method and apparatus are provided for transmitting a Session Initiation Protocol message by a User Equipment in { TAIL ~ an idle mode } in { HEAD ~ an Internet Protocol Multimedia Subsystem system }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD