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

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.

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.

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.