System and method for power control command for device-to-device transmissions
A transmit power control rule for device-to-device (D2D) transmissions may not be necessary during periods in which no uplink transmissions are scheduled to be received by an enhanced Node B base station (eNB). When uplink transmissions are not scheduled to be received by the eNB, the eNB may send a transmit power control (TPC) command to a D2D capable user equipment (D2D UE) that instructs the D2D UE to perform a D2D transmission at a pre-defined transmit power level (e.g., maximum transmit power level). When uplink transmissions are scheduled to be received the eNB, the eNB may send a TPC command to the D2D UE that instructs the D2D UE to perform a D2D transmission at a transmit power level defined by a power control rule.
1. A method for power control command for device-to-device (D2D) communications in a wireless communication network, the method comprising:
establishing, by a base station, a link with a user equipment (UE) in a cell, wherein the UE is configured to perform D2D transmissions to one or more UEs;
sending, by the base station, a first transmit power control (TPC) command to the UE, the first TPC command instructing the UE to perform a first D2D transmission at a pre-defined transmit power level over first time-frequency resources available to carry the first D2D transmission; and
sending, by the base station, a second TPC command to the UE, the second TPC command instructing the UE to perform a second D2D transmission at a transmit power level defined by a power control rule over second time-frequency resources available to carry the second D2D transmission, the transmit power level defined by the power control rule being lower than the pre-defined transmit power level.
2. The method of claim 1 , wherein each TPC command is valid for a specific period.
3. The method of claim 2 , wherein the specific period comprises one or more subframes.
4. The method of claim 2 , wherein the specific period is communicated from the base station to the UE via higher layer signaling.
5. The method of claim 1 , wherein parameters of the power control rule are configured by higher layer signaling.
6. The method of claim 1 , wherein the power control rule comprises an open-loop power control rule.
7. The method of claim 1 , wherein the TPC commands are communicated using a downlink control information (DCI) format.
8. The method of claim 7 , wherein the TPC commands are transmitted on a physical downlink control channel (PDCCH).
9. The method of claim 7 , wherein the TPC commands are transmitted on an enhanced physical downlink control channel (EPDCCH).
10. The method of claim 7 , wherein the DCI format associates the TPC commands with the UE by carrying a radio network temporary identifier (RNTI).
11. The method of claim 1 , wherein the power control rule is in accordance with at least one uplink transmission scheduled to be received by the base station over second time-frequency resources available to carry the second D2D transmission.
12. A base station for power control command for device-to-device (D2D) communications in a wireless communication network, the base station comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions configuring the base station to:
establish a link with a user equipment (UE) in a cell, wherein the UE is configured to perform D2D transmissions to one or more UEs;
send a first transmit power control (TPC) command to the UE, the first TPC command instructing the UE to perform a first D2D transmission to the one or more UEs at a pre-defined transmit power level over first time-frequency resources available to carry the first D2D transmission; and
send a second TPC command to the UE, the second TPC command instructing the UE to perform a second D2D transmission at a transmit power level defined by a power control rule over second time-frequency resources available to carry the second D2D transmission, the transmit power level defined by the power control rule being lower than the pre-defined transmit power level.
13. The base station of claim 12 , wherein the TPC commands are communicated using a downlink control information (DCI) format.
14. The base station of claim 13 , wherein the TPC commands are transmitted on a physical downlink control channel (PDCCH).
15. The base station of claim 13 , wherein the TPC commands are transmitted on an enhanced physical downlink control channel (EPDCCH).
16. The base station of claim 13 , wherein the DCI format associates the TPC commands with the UE by carrying a radio network temporary identifier (RNTI).
17. The base station of claim 12 , wherein each TPC command is valid for a specific period.
18. The base station of claim 17 , wherein the specific period comprises one or more subframes.
19. The base station of claim 17 , wherein the specific period is communicated from the base station to the UE via higher layer signaling.
20. The base station of claim 12 , wherein parameters of the power control rule are configured by higher layer signaling.
21. The base station of claim 12 , wherein the power control rule comprises an open-loop power control rule.
22. The base station of claim 12 , wherein the power control rule is in accordance with at least one uplink transmission scheduled to be received by the base station over second time-frequency resources available to carry the second D2D transmission.