Method and apparatus for reducing push-to-talk (PTT) latency in a WCDMA network

1. A method of reducing latency when setting up a Push-to-Talk (PTT) session from a user terminal in a radio communication network, said method comprising the steps of:

obtaining a radio bearer for the user terminal when a user of the terminal indicates that a PTT session will be requested in the near future;

maintaining the radio bearer during a time period while waiting for the user to request that the PTT session be set up;

sending from the user terminal to the network at least one Heartbeat message having a length exceeding a network threshold for triggering the network to place the user terminal on a Dedicated Channel (DCH),

sending a plurality of Heartbeat messages separated by a time period with a duration shorter than a network time period for removing terminals from the DCH for inactivity;

detecting that the user has requested that the PTT session be set up; and

sending a PTT request message to the network utilizing the radio bearer previously obtained for the user terminal.

2. The method as recited in claim 1 , wherein the step of obtaining a radio bearer includes obtaining a radio bearer for the user terminal when the user of the terminal selects to view PTT contacts information stored in the user terminal.

3. The method as recited in claim 1 , wherein the user of the terminal selects to view PTT contacts information by instructing the terminal to display a page of PTT contacts.

4. The method as recited in claim 1 , wherein the step of detecting that the user has requested that the PTT session be set up includes detecting that the user has pressed a PTT button on the user terminal.

5. The method as recited in claim 1 , wherein the user terminal is a User Equipment (UE) in a Wideband Code Division Multiple Access (WCDMA) network, and the step of sending a request message to the network includes sending a SIP INVITE message to a Call/Session Control Function (CSCF).

6. A method of reducing latency when setting up a Push-to-Talk (PTT) session from a user terminal in a radio communication network, said method comprising the steps of:

obtaining a radio bearer for the user terminal when a user of the terminal opens a PTT application on the terminal;

periodically transmitting a Heartbeat message from the user terminal to the network to maintain the radio bearer while the PTT application is open;

determining whether the user initiates the PTT session or closes the PTT application;

if the user initiates the PTT session, sending a PTT request message to the network utilizing the radio bearer previously obtained for the user terminal; and

if the user closes the PTT application, stopping the transmission of the Heartbeat messages, thereby allowing the network to deallocate the radio bearer.

7. The method as recited in claim 6 , wherein the Heartbeat message has a length that exceeds a network threshold for triggering the network to place the user terminal on a Dedicated Channel (DCH).

8. An apparatus in a user terminal for reducing latency when setting up a Push-to-Talk (PTT) session in a radio communication network, said apparatus comprising:

a user interface for detecting that a user of the terminal has performed an action indicating that a PTT session will be requested in the near future;

a controller in communication with the user interface for obtaining for the user terminal, a radio bearer from the network in response to the user performing the action, wherein the radio bearer is obtained prior to the user requesting the PTT session;

the user terminal maintaining the radio bearer during a time period while waiting for the user to request that the PTT session be set up;

transmission means for sending from the user terminal to the network at least one Heartbeat message having a length exceeding a network threshold for triggering the network to place the user terminal on a Dedicated Channel (DCH) and for

the user terminal sending a plurality of Heartbeat messages separated by a time period with a duration shorter than a network time period for removing terminals from the DCH for inactivity;

means for the user to request the PTT session; and

a transceiver for sending a PTT request message to the network utilizing the radio bearer previously obtained for the user terminal.

9. The apparatus as recited in claim 8 , wherein the user terminal also includes a memory for storing PTT contacts information, and the controller obtains the radio bearer for the user terminal when the user of the terminal selects to view PTT contacts information stored in the user terminal.

10. The apparatus as recited in claim 8 , wherein the means for the user to request the PTT session includes detecting that the user has pressed a PTT button on the user terminal.

11. The apparatus as recited in claim 8 , wherein the user terminal is a User Equipment (UE) in a Wideband Code Division Multiple Access (WCDMA) network, and the PTT request message is a SIP INVITE message sent to a Call/Session Control Function (CSCF).

12. An apparatus in a user terminal for reducing latency when setting up a Push-to-Talk (PTT) session in a radio communication network, wherein the user terminal includes a PTT application and a control processor for running the application, said apparatus comprising:

means for detecting that a user of the terminal has opened the PTT application;

means for obtaining a radio bearer for the user terminal in response to the user opening the PTT application;

means for periodically transmitting a Heartbeat message from the user terminal to the network to maintain the radio bearer while the PTT application is open;

means for determining whether the user initiates the PTT session or closes the PTT application;

means for sending a PTT request message to the network utilizing the radio bearer previously obtained for the user terminal if the user initiates the PTT session; and

means for stopping the transmission of the Heartbeat messages, thereby allowing the network to deallocate the radio bearer, if the user closes the PTT application.

13. The apparatus as recited in claim 12 , wherein the means for periodically transmitting a Heartbeat message includes means for transmitting a Heartbeat message having a length that exceeds a network threshold for triggering the network to place the user terminal on a Dedicated Channel (DCH).