Flexible multiplexing and feedback for variable transmission time intervals
Methods, systems, and devices for wireless communication are described. A base station may employ a multiplexing configuration based on latency and efficiency considerations. The base station may transmit a resource grant, a signal indicating the length of a downlink (DL) transmission time interval (TTI), and a signal indicating the length of a subsequent uplink (UL) TTI to one or more user equipment (UEs). The base station may dynamically select a new multiplexing configuration by, for example, setting the length of an UL TTI to zero or assigning multiple UEs resources in the same DL TTI. Latency may also be reduced by employing block feedback, such as block hybrid automatic repeat request (HARQ) feedback. A UE may determine and transmit HARQ feedback for each transport block (TB) of a set of TBs, which may be based on a time duration of a downlink TTI.
1. A method of wireless communication comprising:
identifying a downlink burst of a time-division duplex (TDD) configured carrier, the downlink burst comprising one or more downlink transmission time intervals (TTIs), wherein respective downlink TTIs of the one or more downlink TTIs have a variable duration;
receiving respective indications of a duration of the respective one or more downlink TTIs, the respective indications received within a first control portion of each of the respective one or more downlink TTIs;
receiving an indication of a duration of an uplink burst that follows the downlink burst, wherein the indication of the duration of the uplink burst is received within a second control portion of each of the respective one or more downlink TTIs, the second control portion being separated in time from the first control portion by a data portion of each of the respective one or more downlink TTIs; and
communicating based at least in part on the respective indications of the duration of the respective one or more downlink TTIs and the indication of the duration of the uplink burst.
2. The method of claim 1 , further comprising:
receiving a downlink grant during a downlink TTI of the respective one or more downlink TTIs, wherein the downlink grant assigns a first set of resources during the downlink TTI.
3. The method of claim 2 , further comprising:
receiving an indication of a duration of a subsequent downlink burst that follows the downlink burst, wherein the indication of the duration of the subsequent downlink burst is received during the subsequent downlink burst;
receiving an indication of a duration of a subsequent uplink burst that follows the subsequent downlink burst, wherein the indication of the duration of the subsequent uplink burst is received during the subsequent downlink burst; and
communicating based at least in part on the indication of the duration of the subsequent downlink burst and the indication of the duration of the subsequent uplink burst.
4. The method of claim 1 , wherein the indication of the duration of the uplink burst indicates that the duration of the uplink burst is zero.
5. The method of claim 4 , wherein the respective one or more downlink TTIs and a subsequent one or more downlink TTIs form a composite downlink burst that is time division multiplexed on resources of the TDD configured carrier.
6. The method of claim 1 , wherein the communicating comprises:
receiving a set of transport blocks (TBs) during the respective one or more downlink TTIs;
determining hybrid automatic repeat request (HARQ) feedback for each TB of the set of TBs, wherein a number of TBs in the set of TBs is based at least in part on the duration of the respective one or more downlink TTIs; and
transmitting the HARQ feedback for at least one TB of the set of TBs during the uplink burst.
7. The method of claim 6 , further comprising:
determining HARQ feedback for a number of code blocks (CBs), wherein each TB of the set of TBs comprises at least one CB, and wherein a quantity of CBs in each TB is based at least in part on a size of each TB; and
transmitting the HARQ feedback for the number of CBs during the uplink burst.
8. The method of claim 1 , further comprising:
entering a low power state during the downlink burst or the uplink burst based at least in part on an absence of a grant of resources in the downlink burst or the uplink burst.
9. An apparatus for wireless communication comprising:
means for identifying a downlink burst of a time-division duplex (TDD) configured carrier, the downlink burst comprising one or more downlink transmission time intervals (TTIs), wherein respective downlink TTIs of the one or more downlink TTIs have a variable duration;
means for receiving respective indications of a duration of the respective one or more downlink TTIs, the respective indications received within a first control portion of each of the respective one or more downlink TTIs;
means for receiving an indication of a duration of an uplink burst that follows the downlink burst, wherein the indication of the duration of the uplink burst is received within a second control portion of each of the respective one or more downlink TTIs, the second control portion being separated in time from the first control portion by a data portion of each of the respective one or more downlink TTIs; and
means for communicating based at least in part on the respective indications of the duration of the respective one or more downlink TTIs and the indication of the duration of the uplink burst.
10. The apparatus of claim 9 , further comprising:
means for receiving a downlink grant during a downlink TTI of the respective one or more downlink TTIs, wherein the downlink grant assigns a first set of resources during the downlink TTI.
11. The apparatus of claim 10 , further comprising:
means for receiving an indication of a duration of a subsequent downlink burst that follows the downlink burst, wherein the indication of the duration of the subsequent downlink burst is received during the subsequent downlink burst;
means for receiving an indication of a duration of a subsequent uplink burst that follows the subsequent downlink burst, wherein the indication of the duration of the subsequent uplink burst is received during the subsequent downlink burst; and
means for communicating based at least in part on the indication of the duration of the subsequent downlink burst and the indication of the duration of the subsequent uplink burst.
12. The apparatus of claim 9 , wherein the indication of the duration of the uplink burst indicates that the duration of the uplink burst is zero.
13. The apparatus of claim 12 , wherein the respective one or more downlink TTIs and a subsequent one or more downlink TTIs form a composite downlink burst that is time division multiplexed on resources of the TDD configured carrier.
14. The apparatus of claim 9 , wherein the means for communicating comprises means for receiving a set of transport blocks (TBs) during the respective one or more downlink TTIs, wherein the apparatus further comprises:
means for determining hybrid automatic repeat request (HARQ) feedback for each TB of the set of TBs, wherein a number of TBs in the set of TBs is based at least in part on the duration of the respective one or more downlink TTIs; and
means for transmitting the HARQ feedback for at least one TB of the set of TBs during the uplink burst.
15. The apparatus of claim 14 , further comprising:
means for determining HARQ feedback for a number of code blocks (CBs), wherein each TB of the set of TBs comprises at least one CB, and wherein a quantity of CBs in each TB is based at least in part on a size of each TB; and
means for transmitting the HARQ feedback for the number of CBs during the uplink burst.
16. The apparatus of claim 9 , further comprising:
means for entering a low power state during the downlink burst or the uplink burst based at least in part on an absence of a grant of resources during the downlink burst or the uplink burst.
17. 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:
identify a downlink burst of a time-division duplex (TDD) configured carrier, the downlink burst comprising one or more downlink transmission time intervals (TTIs), wherein respective downlink TTIs of the one or more downlink TTIs have a variable duration;
receive respective indications of a duration of the respective one or more downlink TTIs, the respective indications received within a first control portion of each of the respective one or more downlink TTIs;
receive an indication of a duration of an uplink burst that follows the downlink burst, wherein the indication of the duration of the uplink burst is received within a second control portion of each of the respective one or more downlink TTIs, the second control portion being separated in time from the first control portion by a data portion of each of the respective one or more downlink TTIs; and
communicate based at least in part on the respective indications of the duration of the respective one or more downlink TTIs and the indication of the duration of the uplink burst.
18. The apparatus of claim 17 , wherein the instructions are operable to cause the apparatus to:
receive a downlink grant during a downlink TTI of the respective one or more downlink TTIs, wherein the downlink grant assigns a first set of resources during the downlink TTI.
19. The apparatus of claim 18 , wherein the instructions are operable to cause the apparatus to:
receive an indication of a duration of a subsequent downlink burst that follows the downlink burst, wherein the indication of the duration of the subsequent downlink burst is received during the subsequent downlink burst;
receive an indication of a duration of a subsequent uplink burst that follows the subsequent downlink burst, wherein the indication of the duration of the subsequent uplink burst is received during the subsequent downlink burst; and
communicate based at least in part on the indication of the duration of the subsequent downlink burst and the indication of the duration of the subsequent uplink burst.
20. The apparatus of claim 17 , wherein the indication of the duration of the uplink burst indicates that the duration of the uplink burst is zero.
21. The apparatus of claim 20 , wherein the respective one or more downlink TTIs and a subsequent one or more downlink TTIs form a composite downlink burst that is time division multiplexed on resources of the TDD configured carrier.
22. The apparatus of claim 17 , wherein the instructions are operable to cause the apparatus to:
receive a set of transport blocks (TBs) during the one or more downlink TTIs;
determine hybrid automatic repeat request (HARQ) feedback for each TB of the set of TBs, wherein a number of TBs in the set of TBs is based at least in part on the duration of the respective one or more downlink TTIs; and
transmit the HARQ feedback for at least one TB of the set of TBs during the uplink burst.
23. The apparatus of claim 22 , wherein the instructions are operable to cause the apparatus to:
determine HARQ feedback for a number of code blocks (CBs), wherein each TB of the set of TBs comprises at least one CB, and wherein a quantity of CBs in each TB is based at least in part on a size of each TB; and
transmit the HARQ feedback for the number of CBs during the uplink burst.
24. The apparatus of claim 17 , wherein the instructions are operable to cause the apparatus to:
enter a low power state during the downlink burst or the uplink burst based at least in part on an absence of a grant of resources during the downlink burst or the uplink burst.
25. A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable to:
identify a downlink burst of a time-division duplex (TDD) configured carrier, the downlink burst comprising one or more downlink transmission time intervals (TTIs), wherein respective downlink TTIs of the one or more downlink TTIs have a variable duration;
receive respective indications of a duration of the respective one or more downlink TTIs, the respective indications received within a first control portion of each of the respective one or more downlink TTIs;
receive an indication of a duration of an uplink burst that follows the downlink burst, wherein the indication of the duration of the uplink burst is received within a second control portion of each of the respective one or more downlink TTIs, the second control portion being separated in time from the first control portion by a data portion of each of the respective one or more downlink TTIs; and
communicate based at least in part on the respective indications of the duration of the respective one or more downlink TTIs and the indication of the duration of the uplink burst.
26. The non-transitory computer-readable medium of claim 25 , wherein the instructions are executable to:
receive a downlink grant during a downlink TTI of the respective one or more downlink TTIs, wherein the downlink grant assigns a first set of resources during the downlink TTI.
27. The non-transitory computer-readable medium of claim 26 , wherein the instructions are executable to:
receive an indication of a duration of a subsequent downlink burst that follows the downlink burst, wherein the indication of the duration of the subsequent downlink burst is received during the subsequent downlink burst;
receive an indication of a duration of a subsequent uplink burst that follows the subsequent downlink burst, wherein the indication of the duration of the subsequent uplink burst is received during the subsequent downlink burst; and
communicate based at least in part on the indication of the duration of the subsequent downlink burst and the indication of the duration of the subsequent uplink burst.
28. The non-transitory computer-readable medium of claim 25 , wherein the indication of the duration of the uplink burst indicates that the duration of the uplink burst is zero.
29. The non-transitory computer-readable medium of claim 25 , wherein the instructions are executable to:
receive a set of transport blocks (TBs) during the respective one or more downlink TTIs;
determine hybrid automatic repeat request (HARQ) feedback for each TB of the set of TBs, wherein a number of TBs in the set of TBs is based at least in part on the duration of the respective one or more downlink TTIs; and
transmit the HARQ feedback for at least one TB of the set of TBs during the uplink burst.
30. The non-transitory computer-readable medium of claim 25 , wherein the instructions are executable to:
enter a low power state during the downlink burst or the uplink burst based at least in part on an absence of a grant of resources during the downlink burst or the uplink burst.
31. The method of claim 1 , wherein the variable duration of the respective one or more downlink TTIs comprises one or more symbol periods having a duration less than a duration of a subframe.
32. The method of claim 1 , wherein the variable duration of the respective one or more downlink TTIs comprises one or more symbol periods having a duration different than a duration of a subframe.