Wideband low latency communication
Methods, systems, and devices for wireless communication are described. A wireless device configured for carrier aggregation may communicate using transport blocks (TBs) mapped according to a wideband configuration that includes resources of multiple component carriers (CCs) within a single, low latency transmission time interval (TTI)—e.g., a TTI that has a shorter duration relative to other TTIs used in the same system. The number of CCs, and thus bandwidth, available for mapping each TB may change dynamically based on the configuration of the CCs. For a CC configured with a control region during a given low latency TTI, a TB sent during that low latency TTI may not be mapped to resources of that CC. In other cases, portions of a CC configured with a control region may be used for wideband configurations. Wideband low latency communications may be used on the uplink or downlink communications, or both.
1. A method of wireless communication using a carrier aggregation (CA) configuration having a first component carrier (CC) and a second CC comprising:
identifying a first transmission time interval (TTI) and a second TTI, wherein the second TTI has a longer duration than the first TTI;
identifying a control channel transmission on the first CC that assigns resources of both of the first CC and the resources of the second CC;
mapping a transport block (TB) within the first TTI according to a wideband configuration that comprises the resources of the first CC and resources of the second CC; and
using the TB to communicate during the first TTI on the resources of the first CC and the resources of the second CC.
2. The method of claim 1 , wherein using the TB to communicate comprises:
transmitting the TB or receiving the TB.
3. The method of claim 1 , further comprising:
using a second TB to communicate, in a different direction than the TB, using a non-wideband configuration that comprises other resources of the first CC or other resources of the second CC.
4. The method of claim 1 , wherein the TB is an uplink (UL) TB or a downlink (DL) TB.
5. The method of claim 1 , further comprising:
identifying a third TTI that has a shorter duration than the second TTI;
mapping a second TB within the third TTI according to a non-wideband configuration that comprises resources of the first CC and excludes resources of the second CC; and
using the second TB to communicate during the third TTI on the resources of the first CC.
6. The method of claim 5 , further comprising:
determining that the second CC comprises at least one of a control region, a multicast-broadcast single frequency network (MBSFN) region, a guard period, an uplink subframe, or a cell-specific reference signal (CRS), or any combination thereof, during the third TTI, wherein mapping the second TB is based at least in part on the determination.
7. The method of claim 1 , wherein the first CC and the second CC use different resource allocation methods or different modulation orders, or both.
8. The method of claim 1 , wherein the resources of the first CC or the resources of the second CC, or both, comprise guard band resources.
9. The method of claim 1 , further comprising:
performing a first channel estimation for the first CC and a second channel estimation for the second CC, wherein the TB is communicated based at least in part on the first channel estimation and the second channel estimation.
10. The method of claim 9 , wherein the first CC has a first cell-specific reference signal (CRS) port configuration and the second CC has a second CRS port configuration, and wherein the first channel estimation is based at least in part on the first CRS port configuration and the second channel estimation is based at least in part on the second CRS port configuration.
11. The method of claim 1 , wherein the first CC and the second CC comprise a same number of demodulation reference signal (DMRS) ports.
12. The method of claim 1 , wherein the first TTI and the second TTI comprise different precoding resource block (RB) group (PRG) configurations.
13. The method of claim 1 , further comprising:
performing a first rate matching procedure for the first CC and a second rate matching procedure for the second CC, wherein the TB is communicated based at least in part on the first rate matching procedure and the second rate matching procedure.
14. The method of claim 1 , wherein a resource allocation scheme for the TB is based at least in part on a number of component carriers (CCs) used for mapping the TB.
15. The method of claim 14 , wherein the resource allocation scheme comprises a frequency diversity scheme or a frequency selectivity scheme.
16. The method of claim 1 , wherein a RB indexing configuration is based at least in part on a bandwidth of the first CC and the second CC.
17. The method of claim 1 , wherein the first TTI comprises two or more symbols, and wherein the mapping for the TB comprises a frequency-first mapping scheme.
18. The method of claim 1 , wherein a code block scheme for the TB is based at least in part on combined resources from the first CC and the second CC.
19. The method of claim 1 , wherein a first portion of the TB is mapped to the resources of the first CC using a first code block scheme and a second portion of the TB is mapped to the resources of the second CC using a second code block scheme.
20. The method of claim 1 , wherein a first modulation and coding scheme (MCS) is used for the first CC and a second MCS is used for the second CC.
21. The method of claim 1 , further comprising:
identifying a same channel state information (CSI) report for the first CC and the second CC.
22. The method of claim 1 , wherein the first CC has a first CSI reference signal (CSI-RS) port configuration and the second CC has a second CSI-RS configuration.
23. The method of claim 1 , wherein a quasi-co-location (QCL) indication is configured for the first CC and the second CC.
24. The method of claim 1 , wherein the resources of the first CC comprise a first uplink shared channel (UL-SCH) cluster and the resources of the second CC comprise a second UL-SCH cluster.
25. The method of claim 1 , further comprising:
performing a joint discrete Fourier transform (DFT) operation on the TB over the first CC and the second CC.
26. The method of claim 1 , further comprising:
communicating using an sounding reference signal (SRS) in a guard band of the first CC or the second CC, or both.
27. An apparatus for wireless communication using a carrier aggregation (CA) configuration having a first component carrier (CC) and a second CC comprising:
means for identifying a first transmission time interval (TTI) and a second TTI, wherein the second TTI has a longer duration than the first TTI;
means for identifying a control channel transmission on the first CC that assigns the resources of both of the first CC and the resources of the second CC;
means for mapping a transport block (TB) within the first TTI according to a wideband configuration that comprises the resources of the first CC and resources of the second CC; and
means for using the TB to communicate during the first TTI on the resources of the first CC and the resources of the second CC.
28. An apparatus for wireless communication using a carrier aggregation (CA) configuration having a first component carrier (CC) and a second CC, 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 a first transmission time interval (TTI) and a second TTI, wherein the second TTI has a longer duration than the first TTI;
identify a control channel transmission on the first CC that assigns the resources of both of the first CC and the resources of the second CC;
map a transport block (TB) within the first TTI according to a wideband configuration that comprises the resources of the first CC and resources of the second CC; and
use the TB to communicate during the first TTI on the resources of the first CC and the resources of the second CC.
29. A non-transitory computer-readable medium storing code for wireless communication using a carrier aggregation (CA) configuration having a first component carrier (CC) and a second CC, the code comprising instructions executable by a processor to:
identify a first transmission time interval (TTI) and a second TTI, wherein the second TTI has a longer duration than the first TTI;
identify a control channel transmission on the first CC that assigns the resources of both of the first CC and the resources of the second CC;
map a transport block (TB) within the first TTI according to a wideband configuration that comprises the resources of the first CC and resources of the second CC; and
use the TB to communicate during the first TTI on the resources of the first CC and the resources of the second CC.