Channel feedback reporting for shared frequency spectrum
Methods, systems, and devices are described for wireless communication. A device may use enhanced reporting mechanisms to support control information reporting on shared spectrum. In some cases, a device may utilize enhanced component carriers (eCCs) for data transmissions. In one example, the device may transmit control information (e.g., ACK/NACK, CSI, etc.) to a corresponding device using a CCA exempt transmission (CET). In another example, a device may report control information quasi-periodically. For instance, a device may be assigned a specified interval and a control feedback window for reporting control information (e.g., CSI). The window may provide a duration prior and subsequent to the specified interval during which a UE may transmit control information. For example, the device may perform a CCA reserving the channel for a duration that does not include the specified interval but may transmit feedback information based on determining the specified interval falls within the assigned window.
1. A method of wireless communication at a user equipment (UE), comprising:
communicating with an evolved node B (eNB) over a frequency channel of a shared frequency band;
receiving a data transmission from the eNB over the frequency channel of the shared frequency band;
determining acknowledgement/negative acknowledgement (ACK/NACK) information for the data transmission; and
transmitting the ACK/NACK information in a clear channel assessment (CCA) exempt feedback transmission to the eNB via the frequency channel of the shared frequency band, wherein the ACK/NACK information is mapped to designated resources of an uplink control channel structure for the CCA-exempt feedback transmission.
2. The method of claim 1 , further comprising:
determining uplink scheduling feedback or channel state information (CSI) feedback; and
transmitting, in the CCA-exempt feedback transmission, the uplink scheduling feedback or the CSI feedback.
3. The method of claim 2 , further comprising:
determining a target modulation and coding scheme (MCS) for a subsequent data transmission based at least in part on channel measurements of one or more reference signals associated with the data transmission; and
wherein the transmitted CSI feedback comprises an indicator associated with the target MCS.
4. The method of claim 3 , further comprising:
identifying a current MCS for the data transmission; and
determining a channel quality delta between the current MCS and the target MCS,
wherein the indicator associated with the target MCS comprises the channel quality delta.
5. The method of claim 3 , wherein the one or more reference signals comprise any of a cell-specific reference signal (CRS), a demodulation reference signal (DM-RS), a UE-specific reference signal (UE-RS), or combinations thereof.
6. The method of claim 5 , wherein the determining the target MCS for the subsequent data transmission comprises estimating a quality of a channel from the eNB based at least in part on the CRS and an identified precoding matrix for the data transmission.
7. The method of claim 1 , wherein the uplink control channel structure comprises a subset of frequency resources of the frequency channel of the shared frequency band.
8. The method of claim 1 , wherein the start of the CCA-exempt feedback transmission occurs less than a predetermined CCA time period from an end of the data transmission.
9. The method of claim 1 , wherein the frequency channel of the shared frequency band comprises an enhanced component carrier (eCC) configured for the UE in a standalone operation mode.
10. The method of claim 1 , further comprising:
receiving a feedback configuration for providing feedback for transmissions over the frequency channel of the shared frequency band, wherein the feedback configuration indicates providing the feedback in the CCA-exempt feedback transmission, a CCA-compliant feedback transmission, or combinations thereof.
11. 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:
communicate with an evolved node B (eNB) over a frequency channel of a shared frequency band;
receive a data transmission from the eNB over the frequency channel of the shared frequency band;
determine acknowledgement/negative acknowledgement (ACK/NACK) information for the data transmission; and
transmit the ACK/NACK information in a clear channel assessment (CCA) exempt feedback transmission to the eNB via the frequency channel of the shared frequency band, wherein the ACK/NACK information is mapped to designated resources of an uplink control channel structure for the CCA-exempt feedback transmission.
12. The apparatus of claim 11 , wherein the instructions are operable to cause to:
determine uplink scheduling feedback or channel state information (CSI) feedback; and
transmit, in the clear channel assessment (CCA)-exempt feedback transmission, the uplink scheduling feedback or the CSI feedback.
13. The apparatus of claim 12 , wherein the instructions are operable to cause to:
determine a target modulation and coding scheme (MCS) for a subsequent data transmission based at least in part on channel measurements of one or more reference signals associated with the data transmission; and
wherein the transmitted CSI feedback comprises an indicator associated with the target MCS.
14. The apparatus of claim 13 , wherein the instructions are operable to cause to:
identify a current MCS for the data transmission; and
determine a channel quality delta between the current MCS and the target MCS, wherein the indicator associated with the target MCS comprises the channel quality delta.
15. The apparatus of claim 13 , wherein the one or more reference signals comprise any of a cell-specific reference signal (CRS), a demodulation reference signal (DM-RS), a UE-specific reference signal (UE-RS), or combinations thereof.
16. The apparatus of claim 15 , wherein the determining the target MCS for the subsequent data transmission comprises estimating a quality of a channel from the eNB based at least in part on the CRS and an identified precoding matrix for the data transmission.
17. The apparatus of claim 11 , wherein the instructions are operable to cause to:
receive a feedback configuration for providing feedback for transmissions over the frequency channel of the shared frequency band, wherein the feedback configuration indicates providing the feedback in the CCA-exempt feedback transmission, a CCA-compliant feedback transmission, or combinations thereof.