Uplink transmission techniques in low-latency wireless communication
Methods, systems, and devices for wireless communications are described that provide for indicating transmit power control information to a user equipment (UE) for semi-persistent scheduling (SPS) transmissions in short transmission time intervals (TTIs) from the UE, and for configuring reference signal transmissions in SPS transmissions of short TTIs. A UE may be configured with uplink power control information for SPS transmissions that use sTTIs that is separate from uplink power control for longer TTIs. A UE may receive the power control information and apply it in SPS transmissions that use sTTIs. Uplink transmit power for SPS sTTI transmissions may be independent of power control for regular sTTI transmissions and independent of power control for long TTI transmissions. UEs may apply a cyclic shift to reference signals transmitted is SPS transmissions according to a SPS configuration, rather than a cyclic shift indicated in a SPS activation command.
1. A method for wireless communication performed by a user equipment (UE), comprising:
receiving a semi-persistent scheduling (SPS) activation for transmitting uplink SPS transmissions in short transmission time intervals (sTTIs), wherein the sTTIs have a first TTI duration that is shorter than a slot;
receiving a first uplink power control information for setting a first uplink transmission power for at least a first uplink transmission in the SPS transmissions;
monitoring, with the SPS activated, a common search space for a power control command;
modifying SPS power according to the power control command;
and
transmitting, after receiving the power control command, an uplink transmission in the SPS transmissions according to the power control command.
2. The method of claim 1 , wherein the power control command is included in downlink control information (DCI).
3. A method for wireless communication performed by a network access node, comprising:
transmitting, to a user equipment (UE), a semi-persistent scheduling (SPS) activation for transmitting uplink SPS transmissions in short transmission time intervals (sTTIs), wherein the sTTIs have a first TTI duration that is shorter than a slot;
transmitting a first uplink power control information for setting a first uplink transmission power at the UE for at least a first uplink transmission in the SPS transmissions;
transmitting, with the SPS activated, a power control command in a common search space; and
receiving, after transmitting the power control command, an uplink transmission in the SPS transmissions according to the power control command.
4. The method of claim 3 , wherein the power control command is included in downlink control information (DCI).
5. An apparatus for wireless communication, comprising:
a processor;
memory coupled with the processor; and
instructions stored in the memory and executable by the processor to cause the apparatus to:
receive a semi-persistent scheduling (SPS) activation for transmitting uplink SPS transmissions in short transmission time intervals (sTTIs), wherein the sTTIs have a first TTI duration that is shorter than a slot;
receive a first uplink power control information for setting a first uplink transmission power a first uplink transmission in the SPS transmissions, monitor, with the SPS activated, a common search space for a power control command;
modify SPS power according to the power control command;
and
transmit, after receiving the power control command, an uplink transmission in the SPS transmissions according to the power control command.
6. The apparatus of claim 5 , wherein the power control command is included in downlink control information (DCI).
7. An apparatus for wireless communication, comprising:
a processor;
memory coupled with the processor; and
instructions stored in the memory and executable by the processor to cause the apparatus to:
transmit, to a user equipment (UE), a semi-persistent scheduling (SPS) activation for transmitting uplink SPS transmissions in short transmission time intervals (sTTIs), wherein sTTIs have a first TTI duration that is shorter than a slot;
transmit first uplink power control information for setting a first uplink transmission power at the UE for at least a first uplink transmission in the SPS transmissions;
transmit, with the SPS activated, a power control command in a common search space; and
receive, after transmitting the power control command, an uplink transmission in the SPS transmissions according to the power control command.
8. A method for wireless communication performed by a UE, comprising:
receiving a semi-persistent scheduling (SPS) activation for transmitting uplink SPS transmissions in short transmission time intervals (sTTIs), wherein the sTTIs have a first TTI duration that is shorter than a slot;
receiving a first transmit power control (TPC) for the SPS transmissions;
receiving a second TPC for a sTTI transmission scheduled by a downlink control information (DCI) grant;
setting, based at least in part on the first TPC and independent of the second TPC, an uplink power for an uplink transmission of the SPS transmission; and
transmitting the uplink transmission of the SPS transmissions using the uplink power.