Fast feedback techniques for high frequency bands in wireless communications systems

A method for wireless communications at a base station, comprising:

• transmitting, to the UE, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band;
• transmitting a downlink message to the UE on the second frequency band;
• and
• receiving, from the UE, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and transmitting the downlink message on the second frequency band, the feedback message comprising a cyclic prefix having the indicated length.

An apparatus for wireless communications at a user equipment (UE), comprising:

• a processor;
• memory in electronic communication with the processor;
• and
• instructions stored in the memory, wherein the instructions are executable by the processor to:
• receive, from the base station, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band;
• monitor the second frequency band for a downlink message from the base station;
• and
• transmit, to the base station, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and on the monitoring the second frequency band, the feedback message comprising a cyclic prefix having the indicated length.

An apparatus for wireless communications at a base station, comprising:

• a processor;
• memory in electronic communication with the processor;
• and
• instructions stored in the memory, wherein the instructions are executable by the processor to:
• transmit, to the UE, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band;
• transmit a downlink message to the UE on the second frequency band;
• and
• receive, from the UE, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and transmitting the downlink message on the second frequency band, the feedback message comprising a cyclic prefix having the indicated length.