Low latency uplink power control
Methods, systems, and devices for wireless communication are described. A user equipment (UE) may determine separate uplink (UL) power limitations for multiple transmission time interval (TTI) durations based on distinct power control parameters. In some cases, an adjustment factor or a power backoff may be applied to communications using one TTI duration to ensure that total transmit power does not exceed a threshold. The UE and the serving base station may also identify one or more demodulation reference signal (DMRS) windows. UL data transmissions may be demodulated based on a DMRS sent during the same window. Transmit power control (TPC) commands may be applied at the beginning of each window. However, if an UL transmission is scheduled at the beginning of the window, the UE may wait until a DMRS transmission or until no more transmissions are scheduled for the window before applying the TPC adjustment.
1. A method of wireless communication, comprising:
identifying, by a first wireless device, a first demodulation reference signal (DMRS) sharing window and a second DMRS sharing window, each of the first DMRS sharing window and the second DMRS sharing window including a discrete set of symbol periods, wherein each symbol period of the discrete set of symbols periods spans a portion of time;
receiving, from a second wireless device, a first transmit power control (TPC) command during the first DMRS sharing window;
receiving, by the first wireless device, a second TPC command during a first symbol period of the discrete set of symbol periods of the second DMRS sharing window, wherein the first symbol period of the second DMRS sharing window precedes a remainder of the discrete set of symbol periods of the second DMRS sharing window;
determining that an uplink (UL) data message is scheduled for transmission during the first symbol period of the second DMRS sharing window such that the second TPC command is received and the UL data message is scheduled for transmission during a same symbol period of the discrete set of symbol periods of the second DMRS sharing window;
determining to use the first TPC command for the UL data message based at least in part on receiving the second TPC command during the first symbol period of the second DMRS sharing window and determining that the UL data message is scheduled for transmission during the first symbol period; and
transmitting, to the second wireless device, the UL data message during the second DMRS sharing window based at least in part on the first TPC command.
2. The method of claim 1 , further comprising:
transmitting, to the second wireless device, a DMRS during the second DMRS sharing window after transmitting the UL data message, wherein the DMRS is transmitted based at least in part on the first TPC command and the second TPC command; and
transmitting, to the second wireless device, a second UL data message after transmitting the DMRS, wherein the second UL data message is transmitted based at least in part on the first TPC command and the second TPC command.
3. An apparatus for wireless communication, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to:
identify, by a first wireless device, a first demodulation reference signal (DMRS) sharing window and a second DMRS sharing window, each of the first DMRS sharing window and the second DMRS sharing window including a discrete set of symbol periods, wherein each symbol period of the discrete set of symbols periods spans a portion of time;
receive, from a second wireless device, a first TPC command during the first DMRS sharing window;
receive, by the first wireless device, a second TPC command during a first symbol period of the discrete set of symbol periods of the second DMRS sharing window, wherein the first symbol period of the second DMRS sharing window precedes a remainder of the discrete set of symbol periods of the second DMRS sharing window;
determine that an uplink (UL) data message is scheduled for transmission during the first symbol period of the discrete set of symbol periods of the second DMRS sharing window such that the second TPC command is received and the UL data message is scheduled for transmission during a same symbol period of the discrete set of symbol periods of the second DMRS sharing window;
determine to use the first TPC command for the UL data message based at least in part on receiving the second TPC command during the first symbol period of the second DMRS sharing window and determining that the UL data message is scheduled for transmission during the first symbol period; and
transmit, to the second wireless device, the UL data message during the second DMRS sharing window based at least in part on the first TPC command.
4. The apparatus of claim 3 , wherein the instructions are further executable to cause the apparatus to:
transmit, to the second wireless device, a DMRS during the second DMRS sharing window after transmitting the UL data message, wherein the DMRS is transmitted based at least in part on the first TPC command and the second TPC command; and
transmit, to the second wireless device, a second UL data message after transmitting the DMRS, wherein the second UL data message is transmitted based at least in part on the first TPC command and the second TPC command.
5. A method for wireless communication, comprising:
identifying, by a first wireless device, a first demodulation reference signal (DMRS) sharing window and a second DMRS sharing window;
receiving, from a second wireless device, a first transmit power control (TPC) command during the first DMRS sharing window;
receiving, by the first wireless device, a second TPC command during the second DMRS sharing window;
determining that an uplink (UL) data message is scheduled for a symbol period different from an initial symbol period of the second DMRS sharing window;
determining to use the second TPC command for the UL data message based at least in part on receiving the second TPC command during the second DMRS sharing window and determining that the UL data message is scheduled for the symbol period different from the initial symbol period; and
transmitting, to the second wireless device, the UL data message during the second DMRS sharing window based at least in part on the first TPC command and the second TPC command.