Method and apparatus for transmitting buffer status report in wireless communication system supporting device to device communication

1. A method of supporting a device-to-device (D2D) communication, the method comprising:

establishing a radio resource control (RRC) connection with an evolved NodeB (eNB);

receiving, by a user equipment (UE), configuration information associated with a D2D communication from the eNB, the configuration information comprising information of a resource selection mode for a D2D data transmission, the information of a resource selection mode indicating a resource pool from which the UE selects a resource for a D2D data transmission to another UE;

identifying, based on a D2D discovery procedure, D2D target identities of a plurality of target UEs;

mapping a D2D target identity of a first target UE, among the plurality of target UEs, to a first group identity, and mapping a D2D target identity of a second target UE, among the plurality of target UEs, to a second group identity;

generating an RRC message to be transmitted to the eNB, the RRC message comprising information of the D2D target identity of the first target UE and information of the D2D target identity of the second target UE;

transmitting the RRC message to the eNB;

generating a MAC-laver message to be transmitted to the eNB, the MAC-layer message comprising a first field that indicates mapping information between the first group identity and the D2D target identity of the first UE and a second field that indicates mapping information between the second group identity and the D2D target identity of the second UE; and

transmitting the MAC-layer message to the eNB.

2. The method of claim 1 , further comprising:

transmitting, to the eNB, a different RRC message comprising changed mapping information between the first group identity and a D2D target identity of a third target UE.

3. The method of claim 2 , wherein the D2D target identity of the first target UE is configured to be identified by Proximity Service (ProSe) Layer-2 identity, and

wherein Prose layer-2 associated with the ProSe Layer-2 identity comprises Media Access Control (MAC) layer, Radio Link Control (RLC) layer, and Packet Data Convergence Protocol (PDCP) layer.

4. The method of claim 1 , wherein a D2D target identity of a group of target UEs is associated with a plurality of target UEs to receive D2 D data transmitted from the UE.

5. The method of claim 1 ,

wherein the MAC-layer message comprises a buffer status report (BSR) associated with a plurality of D2D target identities.

6. The method of claim 5 , further comprising

configuring a Media Access Control Protocol Data Unit (MAC PDU) for the BSR by using logical channel group identity (LCG ID) for indicating a BSR for D2D data or LCG ID for indicating a truncated BSR.

7. The method of claim 2 , wherein the different RRC message is associated with a resource scheduling by the eNB, the resource scheduling indicating a resource for a D2D data transmission of the UE.

8. The method of claim 1 , further comprising:

receiving a System Information Block (SIB) message from the eNB, the SIB message comprising information supporting a D2D data transmission of the UE.

9. The method of claim 8 , wherein the information supporting a D2D data transmission of the UE indicates whether a specific cell supports a D2D data transmission, and

wherein the specific cell is associated with a frequency band through which the UE transmits D2D data.

10. A user equipment (UE) to support a device-to-device (D2D) communication, the UE comprising:

a wireless transceiver to establish a radio resource control (RRC) connection with an evolved NodeR (eNB), and to receive configuration information associated with a D2D communication from the eNB, the configuration information comprising information of a resource selection mode for a D2D data transmission, the information of a resource selection mode indicating a resource pool from which the UE selects a resource for a D2D data transmission to another UE; and

a processor configured to identify, based on a D2D discovery procedure, D2D target identities of a plurality of target UEs,

wherein the processor is configured to map a D2D target identity of a first target UE, among the plurality of target UEs, to a first group identity, and to map a D2D target identity of a second target UE, among the plurality of target UEs, to a second group identity,

wherein the processor is configured to generate an RRC message to be transmitted to the eNB, the RRC message comprising information of the D2D target identity of the first target UE and information of the D2D target identity of the second target UE,

wherein the wireless transceiver transmits the RRC message to the eNB, and

wherein the processor is configured to generate a MAC-layer message to be transmitted to the eNB, the MAC-layer message comprising a first field that indicates mapping information between the first group identity and the D2D target identity of the first UE and a second field that indicates mapping information between the second group identity and the D2D target identity of the second UE.

11. The UE of claim 10 , wherein the processor generates a different RRC message comprising changed mapping information between the first group identity and a D2D target identity of a third target UE, and

the wireless transceiver transmits the different RRC message to the eNB.

12. The UE of claim 11 , wherein the D2D target identity of the first target UE is configured to be identified by Proximity Service (ProSe) Layer-2 identity, and

wherein Prose layer-2 associated with the ProSe Layer-2 identity comprises Media Access Control (MAC) layer, Radio Link Control (RLC) layer, and Packet Data Convergence Protocol (PDCP) layer.

13. The UE of claim 10 , wherein a D2D target identity of a group of target UEs is associated with a plurality of target UEs to receive D2D data transmitted from the UE.

14. The UE of claim 10 ,

wherein the MAC-layer message comprises a buffer status report (BSR) associated with a plurality of D2D target identities.

15. The UE of claim 14 , wherein the processor configures a Media Access Control Protocol Data Unit (MAC PDU) for the BSR by using logical channel group identity (LCG ID) for indicating a BSR for D2D data or LCG ID for indicating a truncated BSR.

16. The UE of claim 11 , wherein the different RRC message is associated with a resource scheduling by the eNB, the resource scheduling indicating a resource for a D2D data transmission of the UE.

17. The UE of claim 10 , wherein the wireless transceiver receives a System Information Block (SIB) message from the eNB, the SIB message comprising information supporting a D2D data transmission of the UE.

18. The UE of claim 17 , wherein the information supporting a D2D data transmission of the UE indicates whether a specific cell supports a D2D data transmission, and

wherein the specific cell is associated with a frequency band through which the UE transmits D2D data.

19. A method of supporting a buffer status report (BSR) associated with a device-to-device (D2D) communication, the method comprising:

receiving, by a user equipment (UE) and from an evolved NodeB (eNB), a first radio resource control (RRC) message comprising configuration information associated with a D2D communication between the UE and another UE;

identifying, based on a D2D discovery procedure, D2D target identities of a plurality of target UEs;

mapping, based on a classification of the plurality of target UEs, a D2D target identity of a first target UE to a first group identity and a D2D target identity of a second target UE to a second group identity;

generating a second RRC message to be transmitted to the eNB, the second RRC message comprising information of the D2D target identity of the first target UE mapped to the first group identity and information of the D2D target identity of the second target UE mapped to the second group identity;

transmitting the second RRC message to the eNB;

generating a MAC-layer message to be transmitted to the eNB, the MAC-layer message comprising a first field that indicates mapping information between the first group identity and the D2D target identity of the first UE and a second field that indicates mapping information between the second group identity and the D2D target identity of the second UE; and

transmitting the MAC-layer message to the eNB.