Low latency physical uplink control channel with scheduling request and channel state information
Methods, systems, and devices for wireless communication are described. A user equipment (UE) and a base station may use low latency communications to improve the throughput of a wireless link. To facilitate efficient low latency communication, the UE may send UE-initiated CSI reports in addition to periodic and base station-initiated reports. For example, the UE may, in various examples, send UE-initiated CSI reports using contention based spectrum, using a request-to-transmit, or using a CSI differential (i.e., an indicator of a change in channel conditions). The base station may schedule different UEs for uplink low latency communication by providing resources to each UE for CSI and scheduling requests (SRs) using coherent or non-coherent uplink transmissions. The CSI and SR may also be combined with uplink feedback.
1. A method of wireless communication, comprising:
determining channel state information (CSI) for a communication link that uses a first transmission time interval (TTI) duration in a system that supports operation with the first TTI duration and a second TTI duration that is greater than the first TTI duration;
identifying resources of an unscheduled uplink channel on which to transmit a report with the determined CSI, wherein the identified resources are reserved for uplink control information (UCI) and a number of resources reserved is based on whether a corresponding transmission is to be a coherent transmission or a non-coherent transmission;
identifying subcarriers of at least a first resource block from the identified resources, wherein a number of subcarriers from the identified resources for the coherent transmission is greater than a number of subcarriers from the identified resources for the non-coherent transmission; and
transmitting the report on the identified resources as the corresponding transmission.
2. The method of claim 1 , wherein transmitting the report on the identified resources comprises:
transmitting the report via a TTI having the first TTI duration, wherein the first TTI duration is two symbols.
3. The method of claim 1 , wherein identifying resources of the unscheduled uplink channel further comprises:
identifying resources for a coherent transmission, wherein the number of resources reserved for UCI for the UE is one-third of available resource units of a symbol.
4. The method of claim 1 , wherein identifying resources of the unscheduled uplink channel further comprises:
identifying resources for a non-coherent transmission, wherein the number of resources reserved for UCI for the UE is one-sixth of available resource units of a symbol.
5. The method of claim 1 , wherein identifying resources of the unscheduled uplink channel further comprises:
identifying the first resource block and a second resource block, each resource block comprising a two symbol TTI, wherein a group of users corresponding to a first symbol of the first resource block is a same group of users corresponding to a second symbol of the second resource block.
6. The method of claim 1 , wherein the identified resources comprise the first resource block and a second resource block, each resource block corresponding to a separate subcarrier of a paired frequency region based at least in part on a frequency hopping configuration.
7. The method of claim 1 , wherein transmitting the report on the identified resources comprises:
transmitting a coherent transmission that comprises a pilot symbol, a scheduling request, and the CSI report.
8. The method of claim 1 , wherein transmitting the report on the identified resources comprises:
transmitting a non-coherent transmission that comprises a scheduling request and the CSI report.
9. The method of claim 1 , wherein the second TTI duration is a subframe including two slots, and wherein the first TTI duration is one slot or less.
10. The method of claim 1 , wherein the report is transmitted with a different cyclic shift from an uplink reference signal.
11. An apparatus for wireless communication, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory and executable by the processor to cause the apparatus to:
determine channel state information (CSI) for a communication link that uses a first transmission time interval (TTI) duration in a system that supports operation with the first TTI duration and a second TTI duration that is greater than the first TTI duration;
identify resources of an unscheduled uplink channel on which to transmit a report with the determined CSI, wherein the identified resources are reserved for uplink control information (UCI) and a number of resources reserved is based on whether a corresponding transmission is to be a coherent transmission or a non-coherent transmission;
identify subcarriers of at least a first resource block from the identified resources, wherein a number of subcarriers from the identified resources for the coherent transmission is greater than a number of subcarriers from the identified resources for the non-coherent transmission; and
transmit the report on the identified resources as the corresponding transmission.
12. The apparatus of claim 11 , wherein the instructions to transmit the report on the identified resources are executable by the processor to cause the apparatus to:
transmit the report via a TTI having the first TTI duration, wherein the first TTI duration is two symbols.
13. The apparatus of claim 11 , wherein the instructions to identify resources of the unscheduled uplink channel further are executable by the processor to cause the apparatus to:
identify resources for a coherent transmission, wherein the number of resources reserved for UCI for the UE is one-third of available resource units of a symbol.
14. The apparatus of claim 11 , wherein the instructions to identify resources of the unscheduled uplink channel further are executable by the processor to cause the apparatus to:
identify resources for a non-coherent transmission, wherein the number of resources reserved for UCI for the UE is one-sixth of available resource units of a symbol.
15. The apparatus of claim 11 , wherein the instructions to identify resources of the unscheduled uplink channel further are executable by the processor to cause the apparatus to:
identify the first resource block and a second resource block, each resource block comprising a two symbol TTI, wherein a group of users corresponding to a first symbol of the first resource block is a same group of users corresponding to a second symbol of the second resource block.
16. The apparatus of claim 11 , wherein the identified resources comprise the first resource block and a second resource block, each resource block corresponding to a separate subcarrier of a paired frequency region based at least in part on a frequency hopping configuration.
17. The apparatus of claim 11 , wherein the instructions to transmit the report on the identified resources are executable by the processor to cause the apparatus to:
transmit a coherent transmission that comprises a pilot symbol, a scheduling request, and the CSI report.
18. The apparatus of claim 11 , wherein the instructions to transmit the report on the identified resources are executable by the processor to cause the apparatus to:
transmit a non-coherent transmission that comprises a scheduling request and the CSI report.
19. The apparatus of claim 11 , wherein the second TTI duration is a subframe including two slots, and wherein the first TTI duration is one slot or less.
20. The apparatus of claim 11 , wherein the report is transmitted with a different cyclic shift from an uplink reference signal.
21. An apparatus for wireless communication, comprising:
means for determining channel state information (CSI) for a communication link that uses a first transmission time interval (TTI) duration in a system that supports operation with the first TTI duration and a second TTI duration that is greater than the first TTI duration;
means for identifying resources of an unscheduled uplink channel on which to transmit a report with the determined CSI, wherein the identified resources are reserved for uplink control information (UCI) and a number of resources reserved is based on whether a corresponding transmission is to be a coherent transmission or a non-coherent transmission;
means for identifying subcarriers of at least a first resource block from the identified resources, wherein a number of subcarriers from the identified resources for the coherent transmission is greater than a number of subcarriers from the identified resources for the non-coherent transmission; and
means for transmitting the report on the identified resources as the corresponding transmission.
22. The apparatus of claim 21 , wherein the means for transmitting the report on the identified resources comprises:
means for transmitting the report via a TTI having the first TTI duration, wherein the first TTI duration is two symbols.
23. The apparatus of claim 21 , wherein the means for identifying resources of the unscheduled uplink channel further comprises:
means for identifying the first resource block and a second resource block, each resource block comprising a two symbol TTI, wherein a group of users corresponding to a first symbol of the first resource block is a same group of users corresponding to a second symbol of the second resource block.
24. The apparatus of claim 21 , wherein the identified resources comprise the first resource block and a second resource block, each resource block corresponding to a separate subcarrier of a paired frequency region based at least in part on a frequency hopping configuration.
25. The apparatus of claim 21 , wherein the means for transmitting the report on the identified resources comprises:
means for transmitting a coherent transmission that comprises a pilot symbol, a scheduling request, and the CSI report.
26. The apparatus of claim 21 , wherein the means for transmitting the report on the identified resources comprises:
means for transmitting a non-coherent transmission that comprises a scheduling request and the CSI report.
27. The apparatus of claim 21 , wherein the means for identifying resources of the unscheduled uplink channel further comprises:
means for identifying resources for a coherent transmission, wherein the number of resources reserved for UCI for the UE is one-third of available resource units of a symbol.
28. The apparatus of claim 21 , wherein the means for identifying resources of the unscheduled uplink channel further comprises:
means for identifying resources for a non-coherent transmission, wherein the number of resources reserved for UCI for the UE is one-sixth of available resource units of a symbol.
29. A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:
determine channel state information (CSI) for a communication link that uses a first transmission time interval (TTI) duration in a system that supports operation with the first TTI duration and a second TTI duration that is greater than the first TTI duration;
identify resources of an unscheduled uplink channel on which to transmit a report with the determined CSI, wherein the identified resources are reserved for uplink control information (UCI) and a number of resources reserved is based on whether a corresponding transmission is to be a coherent transmission or a non-coherent transmission;
identify subcarriers of at least a first resource block from the identified resources, wherein a number of subcarriers from the identified resources for the coherent transmission is greater than a number of subcarriers from the identified resources for the non-coherent transmission; and
transmit the report on the identified resources as the corresponding transmission.
30. The non-transitory computer-readable medium of claim 29 , wherein the code executable to identify resources of the unscheduled uplink channel further comprises instructions executable by the processor to:
identify the first resource block and a second resource block, each resource block comprising a two symbol TTI, wherein a group of users corresponding to a first symbol of the first resource block is a same group of users corresponding to a second symbol of the second resource block.