Method for controlling power saving mode in group communication

1. A method of controlling power saving modes of a plurality of terminals joining in a group communication by a base station, the method comprising:

establishing a group call connection with the plurality of terminals; and

establishing a same power saving mode pattern for the plurality of terminals;

receiving a request message for establishing a power saving mode pattern that is different from the same power saving mode pattern, from a predetermined terminal of the plurality of terminals in which the same power saving mode pattern is established; and

transmitting a response message including information on the different power saving mode pattern to the predetermined terminal, wherein the different power saving mode pattern is applied to the predetermined terminal while the same power saving mode pattern is applied to terminals except the predetermined terminal among the plurality of terminals.

2. The method of claim 1 , wherein the power saving mode pattern comprises a power saving cycle having a listening window and a sleep window.

3. The method of claim 1 , wherein the power saving mode pattern is established when the group call connection is established.

4. The method of claim 1 , wherein establishing the power saving mode pattern comprises transmitting messages including information on the power saving mode pattern to the plurality of terminals by unicast, respectively.

5. The method of claim 1 , wherein establishing the power saving mode pattern comprises transmitting a message including information on the power saving mode pattern to the plurality of terminals by multicast.

6. The method of claim 1 , further comprising:

receiving a request message for changing the power saving mode pattern from a predetermined terminal of the plurality of terminals; and

transmitting a response message including information on a changed power saving mode pattern to the plurality of terminals by multicast.

7. The method of claim 1 , further comprising allocating a same identifier to the plurality of terminals, for controlling power saving modes of the plurality of terminals.

8. The method of claim 7 , further comprising transmitting a traffic indication message to the plurality of terminals when traffic to be transmitted to the plurality of terminals exists,

wherein the traffic indication message comprises the identifier.

9. A method of controlling a power saving mode by a terminal joining in a group communication, the method comprising:

establishing a group call connection with a base station;

establishing a same power saving mode pattern as other terminals joining in the group communication; and

entering a power saving mode according to the power saving mode pattern;

when the same power saving mode pattern as the other terminals is established in the terminal, transmitting a request message for establishing a power saving mode pattern that is different from the same power saving mode pattern, to the base station; and

receiving a response message including information on the different power saving mode pattern from the base station, wherein the terminal operates with the different power saving mode pattern in the power saving mode while the other terminals operate with the same power saving mode pattern.

10. The method of claim 9 , further comprising entering the power saving mode when other service connection is released and no burst for the group call exists.

11. The method of claim 9 , wherein the power saving mode pattern comprises a power saving cycle having a listening window and a sleep window.

12. The method of claim 9 , wherein the power saving mode pattern is established when the group call connection is established.

13. The method of claim 9 , wherein establishing the power saving mode pattern comprises receiving a messages including information on the power saving mode pattern from the base station.

14. The method of claim 9 , further comprising:

transmitting a request message for changing the power saving mode pattern to the base station; and

receiving a response message including information on a changed power saving mode pattern from the base station.

15. The method of claim 14 , wherein the terminal is a terminal with a highest priority among a plurality of terminals.

16. The method of claim 9 , further comprising receiving an identifier from the base station, the identifier being equally allocated to a plurality of terminals for controlling power saving modes of the plurality of terminals.

17. The method of claim 16 , further comprising:

receiving a traffic indication message from the base station in a listening window of the power saving mode; and

checking whether the identifier exists in the traffic indication message.

18. The method of claim 9 , wherein the power saving mode pattern comprises a power saving cycle having a listening window and a sleep window, and

wherein the method further comprises:

establishing a connection for other service, and

setting a sleep window that is common to the sleep window according to the power saving mode pattern and a sleep window of the other service as a new sleep window when a traffic burst for the other service is terminated.