Method and apparatus of scheduling for device to device (D2D) communication

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

generating, at an evolved NodeB (eNB), D2D scheduling assignment (D2D SA) grant associated with a transmission (Tx) UE;

transmitting the generated D2D SA grant to the Tx UE, the D2D SA grant enabling the Tx UE to transmit SA#0 to a reception (Rx) UE through a D2D communication, wherein the SA#0 is associated with first resources of a first multiple transmission opportunities (MTO) of a first period;

generating, at the eNB, a D2D data grant associated with the Tx UE;

transmitting the generated D2D data grant to the Tx UE, the D2D data grant enabling the Tx UE to transmit Transport Block #0 (TB#0) to the Rx UE, wherein the TB#0 is associated with second resources of a second MTO of the first period;

generating a separate grant for indicating overriding of the D2D SA grant, wherein the overriding replaces a scheduled transmission of the SA#0 in the first MTO of the first period with a transmission of SA-#1 in the first MTO of the first period, and wherein the SA#1 is associated with third resources, of the first MTO, that are different from the first resources; and

transmitting, by the eNB and to the Tx UE, the generated separate grant, the separate grant enabling the Tx UE to transmit, via the third resource, the SA#1 to the Rx UE.

2. The method of claim 1 , further comprising:

receiving a scheduling request (SR) message or a buffer state report (BSR) message from the Tx UE,

wherein the separate grant is generated based on the SR message or the BSR message.

3. The method of claim 1 , wherein:

the D2D data grant informs the Tx UE of transmitting the TB#0 to the Rx UE in the second MTO;

the TB#0 transfers D2D data; and

the separate grant comprises an overriding flag bit indicating a transmission of Transport Block #1 (TB#1) on the second MTO.

4. The method of claim 3 , wherein:

the D2D data grant comprises a resource pattern for transmission (RPT) for transmitting the TB#0 on the second MTO; and

the separate grant indicates that the TB#1 is based on the RPT.

5. The method of claim 3 , wherein the separate grant comprises at least one of modulation coding scheme (MCS), transmission power command (TPC), and timing alignment (TA) as control information for the transmission of the TB#1.

6. A method of supporting a device-to-device (D2D) communication between user equipments (UEs), the method comprising:

receiving, at a transmission (Tx) UE, D2D scheduling assignment (D2D SA) grant transmitted from an evolved NodeB (eNB), the D2D SA grant enabling the Tx UE to transmit SA#0 to a reception (Rx) UE through a D2D communication, wherein the SA#0 is associated with first resources of a first multiple transmission opportunities (MTO) of a first period;

receiving, at the Tx UE, a D2D data grant transmitted from the eNB, the D2D data grant enabling the Tx UE to transmit a Transport Block #0 (TB#0) to the Rx UE, wherein the TB#0 is associated with second resources of a second MTO of the first period;

scheduling, based on the D2D SA grant, the transmission of the SA#0 on the first resources;

scheduling, based on the D2D data grant, the transmission of the TB#0 on the second resources;

receiving, at the Tx UE, a separate grant for indicating overriding of the D2D SA grant;

replacing, by the Tx UE and based on the separate grant, the scheduled transmission of SA#0 in the first MTO of the first period with a transmission of SA#1 in the first MTO of the first period, wherein the SA#1 is associated with third resources, of the first MTO, that are different from the first resources;

transmitting, by the Tx UE and to the Rx UE, the SA#1 via the third resources; and

transmitting, by the Tx UE and to the Rx UE, TB#1 via fourth resources of the second MTO.

7. The method of claim 6 , further comprising:

replacing the scheduled transmission of TB#0 with a transmission of TB#1,

wherein the separate grant enables the Tx UE to transmit, to the Rx UE, the TB#1 in replacement of the TB#0.

8. The method of claim 7 , further comprising:

transmitting a scheduling request (SR) message or a buffer state report (BSR) message to the eNB,

wherein the separate grant is generated based on the SR message or the BSR message.

9. The method of claim 7 , wherein:

the separate grant comprises an overriding flag bit indicating a transmission of the TB#1 on the second MTO.

10. The method of claim 7 , wherein:

the D2D data grant comprises a resource pattern for transmission (RPT) for transmitting the TB#0 on the second MTO; and

the separate grant indicates that the TB#1 is based on the RPT.

11. The method of claim 7 , wherein the separate grant comprises at least one of modulation coding scheme (MCS), transmission power command (TPC), and timing alignment (TA) as control information for the transmission of the TB#1.

12. The method of claim 6 , wherein the replacement of the scheduled transmission of SA#0 with the transmission of SA#1 occurs in m th subframe after the subframe in which the separate grant is transmitted, where m is an integer.

13. The method of claim 6 , wherein the transmission of SA#1 is indicated based on Demodulation Reference Signal (DM-RS).

14. An evolved NodeB (eNB) to support a device-to-device (D2D) communication between user equipments (UEs), the eNB comprising:

a processor configured to generate D2D scheduling assignment (D2D SA) grant associated with a transmission (Tx) UE and generate a D2D data grant associated with the Tx UE; and

a transmitter to transmit, to the Tx UE, the generated D2D SA grant and the generated D2D data grant, the D2D SA grant enabling the Tx UE to transmit SA#0 to a reception (Rx) UE through a D2D communication, the D2D data grant enabling the Tx UE to transmit Transport Block #0 (TB#0) to the Rx UE, wherein SA#0 is associated with first resources of a first multiple transmission opportunities (MTO) of a first period, and wherein the TB#0 is associated with second resources of a second MTO of the first period,

wherein the processor is configured to generate a separate grant for indicating overriding of the D2D SA grant, wherein the overriding replaces a scheduled transmission of the SA#0 in the first MTO of the first period with a transmission of SA#1 in the first MTO of the first period, and wherein the SA#1 is associated with third resources, of the first MTO, that are different from the first resources, and

wherein the transmitter transmits, to the Tx UE, the generated separate grant, the separate grant enabling the Tx UE to transmit, via the third resources, the SA#1 to the Rx UE.

15. A transmission user equipment (Tx UE) to perform a device-to-device (D2D) communication with a reception UE (Rx UE), the Tx UE comprising:

a transmitter;

a receiver to receive D2D scheduling assignment (D2D SA) grant transmitted from an evolved NodeB (eNB) and receive a D2D data grant transmitted from the eNB, the D2D SA grant enabling the Tx UE to transmit SA#0 to a reception (Rx) UE through a D2D communication, the D2D data grant enabling the Tx UE to transmit a Transport Block #0 (TB#0) to the Rx UE, wherein the SA#0 is associated with first resources of a first multiple transmission opportunities (MTO) of a first period, and wherein the TB#0 is associated with second resources of a second MTO of the first period; and

a processor configured to schedule, based on the D2D SA grant the transmission of SA#0 on the first resources and schedule, based on the D2D data grant, the transmission of TB#0 on the second resources,

wherein: the receiver receives a separate grant for indicating overriding of the D2D SA grant;

based on the separate grant, the processor is configured to replace the scheduled transmission of SA#0 in the first MTO of the first period with a transmission of SA#1 in the first MTO of the first period;

the SA#1 is associated with third resources, of the first MTO, that are different from the first resources; and

the transmitter transmits, to the Rx UE, the SA#1 via the third resources and TB#1 via fourth resources of the second MTO.

16. The Tx UE of claim 15 , wherein the processor is configured to replace the scheduled transmission of TB#0 with a transmission of TB#1; and

wherein the separate grant enables the Tx UE to transmit, to the RX UE, the TB#1 in replacement of TB#0.

17. The Tx UE of claim 15 , wherein:

the separate grant comprises an overriding flag bit indicating a transmission of the TB#1 on the second MTO.

18. The Tx UE of claim 15 , wherein:

the D2D data grant comprises a resource pattern for transmission (RPT) for transmitting the TB#0 on the second MTO; and

the separate grant indicates that the TB#1 is based on the RPT.