1. A Push To Talk (PTT) over Cellular (PoC) system for establishing and managing a multimedia PoC session for performing a multimedia call service, the PoC system comprising:
a session establishment request PoC client for transmitting a session participation request (INVITE) message containing media type and media attribute information to a PoC server; and
the PoC server for storing the media type and media attribute information contained in the INVITE message, and if a first response message is received, transmitting a response message, which indicates that media types contained in the first response message are in a transportable state, to the session establishment request PoC client in order to establish a PoC session supporting only the media types set for media transmission in the first response message.
2. The PoC system of claim 1, wherein the PoC server compares the media types contained in the first response message and the stored media types, and if the media types are all the same, the PoC server transmits a response message, which indicates that all the stored media types are in the transportable state, to the session establishment request PoC client.
3. The PoC system of claim 2, wherein the PoC server inserts User Datagram Protocol (UDP) port numbers assigned to transportable media and a media feature value indicating that corresponding media types can be transmitted in the response message that is to be transmitted to the session establishment request PoC client.
4. The PoC system of claim 1, wherein the PoC server compares the media types contained in the first response message and the stored media types, and if the media types are not all the same, the PoC server transmits a response message, which indicates that only the media types contained in the first response message are in the transportable state, to the session establishment request PoC client.
5. The PoC system of claim 4, wherein the PoC server inserts User Datagram Protocol (UDP) port numbers assigned to transportable media and a media feature value indicating that corresponding media types can be transmitted in the response message that is to be transmitted to the session establishment request PoC client.
6. The PoC system of claim 1, wherein if a response message received in response to the INVITE message is not the first response message, and if media types contained in the response message are a portion of media types supported by a session established between the session establishment request PoC client and the PoC server, the PoC server does not update the session.
7. The PoC system of claim 1, wherein if a response message received in response to the INVITE message is not the first response message, and if media types contained in the response message are different from media types supported by a session established between the session establishment request PoC client and the PoC server, the PoC server updates the session so that the newly supported media types are in the transportable state.
8. The PoC system of claim 7, wherein when the PoC server updates the session so that the newly supported media types are in the transportable state, the PoC server performs the session update according to media attributes of the stored media types.
9. The PoC system of claim 7, wherein the PoC server transmits a re-INVITE message containing UDP port numbers assigned to the media types newly supported for the session update to the session establishment request PoC client.
10. The PoC system of claim 7, wherein when UDP port numbers are assigned to all the media types in the initial session establishment, and when the PoC server receives a newly supported media type and transmits a message for updating to a media feature value indicating that the media type can be transmitted, the message for updating is a Media Burst Control Protocol (MBCP) message using a Real-time Transport Control Protocol (RTCP) channel.
11. A method of establishing and managing a multimedia Push To Talk (PTT) over Cellular (PoC) session for performing a multimedia call service in a PoC system comprising a session establishment request PoC client, at least one session participation PoC client, and a PoC server for establishing and managing the multimedia PoC session, the method comprising:
a first process, wherein the session establishment request PoC client transmits a session participation request (INVITE) message containing media type and media attribute information to the PoC server;
a second process, wherein the PoC server stores the media type and media attribute information contained in the INVITE message; and
a third process, wherein if a first response message is received, the PoC server establishes a PoC session by transmitting a response message, which indicates that media types contained in the first response message are in a transportable state, to the session establishment request PoC client.
12. The method of claim 11, wherein the third process comprises:
the PoC server comparing the media types contained in the first response message and the stored media types; and
if the media types contained in the first response message are the same as the stored media types, transmitting a response message, which indicates that all the stored media types are in the transportable state, to the session establishment request PoC client.
13. The method of claim 12, further comprising if the media types are not all the same as a result of the comparison, transmitting a response message, which indicates that only the media types contained in the first response message are in the transportable state, to the session establishment request PoC client.
14. The method of claim 12, wherein the PoC server inserts User Datagram Protocol (UDP) port numbers assigned to the transportable media in the response message that is to be transmitted to the session establishment request PoC client.
15. The method of claim 13, wherein the PoC server inserts User Datagram Protocol (UDP) port numbers assigned to transportable media in the response message that is to be transmitted to the session establishment request PoC client.
16. The method of claim 12, further comprising:
a fourth process, wherein if a response message received in response to the INVITE message is not the first response message, it is determined whether media types contained in the response message are a portion of media types supported by a session established between the session establishment request PoC client and the PoC server; and
a fifth process, wherein if it is determined that the media types contained in the response message are a portion of the media types supported by the session established between the session establishment request PoC client and the PoC server, the PoC server does not update the session.
17. The method of claim 16, further comprising if it is determined that the media types contained in the response message are different from the media types supported by the session established between the session establishment request PoC client and the PoC server, updating the session so that the newly supported media types are in the transportable state.
18. The method of claim 17, wherein when the PoC server updates the session so that the newly supported media types are in the transportable state, the PoC server performs the session update according to media attributes of the stored media types contained in the INVITE message.
19. The method of claim 17, wherein the PoC server transmits a re-INVITE message containing UDP port numbers assigned to the media types newly supported for the session update to the session establishment request PoC client.
20. The method of claim 17, wherein when UDP port numbers are assigned to all the media types in the initial session establishment, and when the PoC server receives a newly supported media type and transmits a message for updating to a media feature value indicating that the media type can be transmitted, the message for updating is a Media Burst Control Protocol (MBCP) message using a Real-time Transport Control Protocol (RTCP) channel.
21. A User Equipment (UE) for establishing and managing a multimedia Push To Talk (PTT) over Cellular (PoC) session for performing a multimedia call service in a PoC system, the UE comprising:
a data transmitter for performing transmission and reception of packet data with a PoC server; and
a controller for controlling the data transmitter to transmit a session participation request (INVITE) message containing media type and media attribute information required for session establishment, and if a re-INVITE message containing specific media type information supported in a current session is received, to transmit a response message in response to the re-INVITE message.
22. The UE of claim 21, wherein if an INVITE message is received, the controller controls the data transmitter to transmit a response message containing supportable media type information, in response to the INVITE message.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A circuit comprising:
an active pull-up device coupled to a one-wire bus, wherein the active pull-up device is configured to decrease the transition time of a voltage signal on the one-wire bus transitioning from a first voltage level to a second, higher voltage level; and
a level shift circuit coupled to the active pull-up device to circuit ground, said level shift circuit providing a substantially constant reference voltage level different than said circuit ground, wherein the active pull-up device is configured to operate with respect to the constant reference voltage level for decreasing the transition time of said voltage signal.
2. The circuit of claim 1 wherein the one-wire bus is a hi-directional one-wire bus for hi-directional communications, and the active pull-up device switches from a first impedance to a second, lower impedance when the voltage signal rises above a designated threshold voltage level between the first and second voltage levels, for decreasing said transition time of the voltage signal due to parasitic capacitances on the one-wire bus.
3. The circuit of claim 2 wherein:
the voltage signal on the one-wire bus includes a bias signal equal to the reference voltage level; and
the active pull-up device has a voltage sense switch that is coupled to the level shift circuit, said active pull-up device being configured to initiate the decrease of said transition time when the voltage sense switch determines that a measured level of the voltage signal has risen above the designated threshold voltage level, said voltage signal being measured with respect to said reference voltage level.
4. The circuit of claim 2 where the level shift circuit is a diode with its cathode connected to circuit ground and its anode connected to a reference connection point of the active pull-up device.
5. The circuit of claim 2 further comprising:
at least one communication device coupled to the one-wire bus and configured to output said voltage signal for communicating over the one-wire bus, wherein the at least one communication device is configured to include a bias signal equal to the reference voltage level in the voltage signal.
6. The circuit of claim 5 further comprising:
a transceiver having a processor, wherein the transceiver is coupled to the one wire bus and is configured to communicate with said at least one communication device over said one-wire bus, wherein communication signals generated by the transceiver are biased by said reference voltage level.
7. A circuit comprising:
a level shift circuit connected to a circuit ground and configured to output a substantially constant reference voltage level different than said circuit ground; and
an active pull-up device coupled to the level shift circuit and to a one-wire bus for bi-directional communications wherein the active pull-up device is configured to output a first designated voltage level on the one-wire bus when a measured voltage level of a communication signal on the bus rises above a second designated voltage level, said second voltage level being less than the first voltage level said active pull-up device measuring the voltage level of the communication signal with respect to the constant reference voltage; and
wherein the active pull-up device decreases a transition time of the communication signal on the one-wire bus transitioning from the second voltage level to the first voltage level.
8. The circuit of claim 7 wherein:
the active pull-up device switches from a first impedance to a second, lower impedance when the measured voltage level of the communication signal on the bus rises above the second designated voltage level, for decreasing said transition time of the communication signal; and
the communication signal includes a bias signal equal to the reference voltage level.
9. The circuit of claim 8 wherein the level shift circuit is a diode with its cathode connected to circuit ground and its anode connected to a reference connection point of the active pull-up device.
10. The circuit of claim 7 further comprising:
at least one communication device coupled to the one-wire bus and configured to output said voltage signal for communicating over the one-wire bus, wherein the at least one communication device is configured to include a bias signal equal to the reference voltage level in the voltage signal.
11. The circuit of claim 10 further comprising:
a transceiver having a processor, wherein the transceiver is coupled to the one wire bus and is configured to communicate with said at least one communication device over said one-wire bus, wherein communication signals generated by the transceiver are biased by said reference voltage level.
12. A communication system comprising:
a one-wire bus for bi-directional communications:
a transceiver connected to the one-wire bus;
a communication device connected to the one wire-bus, wherein the communication device is configured to apply a voltage signal to the bus for communicating with the transceiver;
an active pull-up device connected to the one-wire bus and configured decrease the transition time of the voltage signal on the one-wire bus when transitioning from a first voltage level to a second, higher voltage level, when the voltage signal passes above a threshold level; and
a level shift circuit disposed between the active pull-up device and a circuit ground, said level shift circuit providing a substantially constant reference voltage level above or below said circuit ground, wherein the active pull-up device is configured to operate with respect to the constant reference voltage level, and wherein the voltage signal applied by the communication device includes a bias voltage equal to said constant reference voltage level.