Coverage enhancements with carrier aggregation
Methods, systems, and devices are described for effective deployment of coverage enhancements in applications involving carrier aggregation or reception-limited devices, or both. Different categories of user equipment (UE) may be configured to receive simultaneous broadcasts and unicasts differently according physical limitations of each category of UE. Several component carriers may be utilized, and each may employ the same or different coverage enhancement techniques. Differences in coverage enhancement techniques may be accounted for with numbers and timing of hybrid automatic repeat request (HARM) processes, soft buffer partitioning, channel bundling, and/or transmission prioritization. UEs may determine to cease transmission of one or more component carriers based on different priorities assigned to the component carriers.
1. A method of wireless communication at a user equipment (UE), comprising:
receiving a first component carrier transmitted according to a first coverage enhancement technique;
receiving a second component carrier transmitted according to a second coverage enhancement technique, wherein at least one of the first or the second coverage enhancement technique comprises bundling and the second coverage enhancement technique is different from the first coverage enhancement technique, wherein one or more uplink control channels and one or more downlink control channels are allocated to a component carrier having the least bundling;
partitioning a soft buffer for the first and second component carriers, wherein the first component carrier is configured with a set number of hybrid automatic repeat request (HARQ) processes that is set based at least in part on the first coverage enhancement technique and the second component carrier is restricted to a same number of HARQ processes as the set number of HARQ processes;
measuring path loss of the first component carrier and the second component carrier; and
selecting, for initial access, the first component carrier or the second component carrier based at least in part on the measured path loss.
2. The method of claim 1 , wherein the first coverage enhancement technique and the second coverage enhancement technique each comprise bundling, and wherein a difference between the first coverage enhancement technique and the second coverage enhancement technique comprises a difference in bundling size that is based at least in part on the number of consecutive transmission time intervals (TTIs) transmitted in a bundled transmission.
3. The method of claim 1 , further comprising:
measuring path loss of the first component carrier and the second component carrier; and
transmitting feedback based on the measured path loss, the feedback comprising a suggested primary cell (PCell).
4. The method of claim 1 , further comprising:
partitioning the soft buffer equally for the first and second component carriers, wherein a bundling length is different for each of the first and second component carriers.
5. The method of claim 1 , further comprising:
partitioning the soft buffer based on a bundling length for each of the first and second component carriers, wherein the bundling length is different for each of the first and second component carriers.
6. The method of claim 1 , wherein the first component carrier and the second component carrier belong to a subset of a plurality of component carriers received at the UE, and wherein each component carrier of the subset needs coverage enhancement and is restricted to a same number of HARQ processes.
7. The method of claim 1 , further comprising:
receiving a third component carrier transmitted without coverage enhancement, wherein the third component carrier is configured with an unrestricted number of HARQ processes.
8. The method of claim 1 , further comprising:
determining which component carrier has the least bundling, wherein:
the first coverage enhancement technique and the second coverage enhancement technique each comprise bundling; and
all control channels are allocated to the component carrier having the least bundling.
9. The method of claim 1 , further comprising:
identifying a downlink (DL) HARQ timing based on whether the first component carrier comprises a bundled or an unbundled control channel.
10. The method of claim 1 , wherein:
at least one of the first coverage enhancement technique or the second coverage enhancement technique comprises channel repetition; and
a length of the channel repetition is interpreted by the UE based on a category of the UE.
11. The method of claim 10 , wherein at least one of the first component carrier or the second component carrier comprises a broadcast channel.
12. An apparatus for wireless communication, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, the instructions executable by the processor to cause the apparatus to:
receive a second component carrier transmitted according to a second coverage enhancement technique, wherein at least one of the first or the second coverage enhancement technique comprises bundling and the second coverage enhancement technique is different from the first coverage enhancement technique, wherein one or more uplink control channels and one or more downlink control channels are allocated to a component carrier having the least bundling; and
partitioning a soft buffer for the first and the second component carriers, wherein the first component carrier is configured with a set number of hybrid automatic repeat request (HARQ) processes that is set based at least in part on the first coverage enhancement technique and the second component carrier is restricted to a same number of HARQ processes as the set number of HARQ processes;
measure path loss of the first component carrier and the second component carrier; and
select, for initial access, the first component carrier or the second component carrier based at least in part on the measured path loss.
13. The apparatus of claim 12 , wherein the first coverage enhancement technique and the second coverage enhancement technique each comprise bundling, and wherein a difference between the first coverage enhancement technique and the second coverage enhancement technique comprises a difference in bundling size that is based at least in part on the number of consecutive transmission time intervals (TTIs) transmitted in a bundled transmission.
14. The apparatus of claim 12 , wherein the instructions are executable by the processor to cause the apparatus to:
measure path loss of the first component carrier and the second component carrier; and
transmit feedback based on the measured path loss, the feedback comprising a suggested primary cell (PCell).
15. The apparatus of claim 12 , wherein the instructions are executable by the processor to cause the apparatus to:
partition the soft buffer equally for the first and second component carriers, wherein a bundling length is different for each of the first and second component carriers.
16. The apparatus of claim 12 , wherein the instructions are executable by the processor to cause the apparatus to:
partition the soft buffer based on a bundling length for each of the first and second component carriers, wherein the bundling length is different for each of the first and second component carriers.
17. The apparatus of claim 12 , wherein the instructions are executable by the processor to cause the apparatus to:
receive a third component carrier transmitted without coverage enhancement, wherein the third component carrier is configured with an unrestricted number of HARQ processes.
18. The apparatus of claim 12 , wherein the first component carrier and the second component carrier belong to a subset of a plurality of component carriers received at a user equipment (UE), and wherein each component carrier of the subset needs coverage enhancement and is restricted to a same number of HARQ processes.
19. The apparatus of claim 12 , wherein the instructions are executable by the processor to cause the apparatus to:
determine which component carrier has the least bundling, wherein:
the first coverage enhancement technique and the second coverage enhancement technique each comprise bundling; and
all control channels are allocated to the component carrier having the least bundling.
20. The apparatus of claim 12 , wherein the instructions are executable by the processor to cause the apparatus to:
identify a downlink (DL) HARQ timing based on whether the first component carrier comprises a bundled or an unbundled control channel.
21. The apparatus of claim 12 , wherein:
at least one of the first coverage enhancement technique or the second coverage enhancement technique comprises channel repetition; and
a length of the channel repetition is interpreted by a user equipment (UE) based on a category of the UE.
22. The apparatus of claim 21 , wherein at least one of the first component carrier or the second component carrier comprises a broadcast channel.