Search space overbooking and pruning
Methods, systems, and devices for wireless communication are described. In some cases, due to blind decoding and channel estimation (CE) limits, one or more user equipment (UE) specific search sets may be pruned for blind decoding and/or CE purposes. For instance, after hashing a set of common decoding candidates to control channel elements (CCEs) within the control region, the UE specific search sets may be pruned so as to conform to the blind decode limitation, since a common search space has already occupied a portion of the total blind decode limit. Following pruning, the UE may hash the sets of UE-specific decoding candidates associated with the one or more UE specific search sets to CCEs within the control region. The UE may further prune UE specific search sets, based on CE limits, while reusing CE for overlapping hashed locations.
1. A method for wireless communication at a base station, comprising:
identifying, for a control region of a control channel, one or more sets of decoding candidates associated with one or more search space sets;
determining a total number of available control channel elements (CCEs) for the one or more search space sets based at least in part on a CCE channel estimation limitation of a user equipment (UE);
determining respective numbers of available CCEs for the one or more search space sets based at least in part on the total number of available CCEs;
determining an applied one or more sets of decoding candidates by hashing a first subset of the one or more sets of decoding candidates associated with a common search space set to a first subset of CCEs of the control region based at least in part on the total number of available CCEs;
admitting, to the applied one or more sets of decoding candidates, a second subset of the one or more sets of decoding candidates associated with a UE-specific search space set having hashed locations overlapping with the first subset of CCEs; and
transmitting control information to the UE via the control channel over at least one of the applied one or more sets of decoding candidates of the control region.
2. The method of claim 1 , further comprising:
determining a total number of available blind decodes for the one or more search space sets based at least in part on a blind decoding limitation of the UE;
determining respective numbers of available blind decodes for the one or more search space sets based at least in part on the total number of available blind decodes; and
pruning the one or more sets of decoding candidates based at least in part on the respective numbers of available blind decodes for the one or more search space sets.
3. The method of claim 2 , wherein the determining the respective numbers of available blind decodes comprises allocating the total number of available blind decodes for the one or more search space sets to the one or more search space sets in proportion to respective numbers of decoding candidates in the one or more search space sets.
4. The method of claim 2 , wherein the determining the respective numbers of available blind decodes comprises uniformly allocating the total number of available blind decodes to the one or more search space sets.
5. The method of claim 2 , wherein the determining the respective numbers of available blind decodes comprises allocating a minimum number of blind decodes to each of the one or more search space sets.
6. The method of claim 2 , wherein the one or more sets of decoding candidates comprise one or more sets of UE-specific decoding candidates of one or more UE-specific search space sets, the method further comprising:
identifying, for the control region, a set of common decoding candidates associated with the common search space set; and
hashing the set of common decoding candidates to a second subset of CCEs of the control region, wherein the total number of available blind decodes is determined based at least in part on a number decoding candidates of the set of common decoding candidates and the blind decoding limitation of the UE.
7. The method of claim 1 , wherein the determining the respective numbers of available CCEs for the one or more sets of decoding candidates comprises:
allocating the total number of available CCEs to the one or more search space sets in proportion to respective numbers of CCEs spanned by respective sets of decoding candidates in the one or more search space sets.
8. The method of claim 1 , wherein the determining the respective numbers of available CCEs for the one or more sets of decoding candidates comprises:
uniformly allocating the total number of available CCEs to the one or more search space sets, allocating a minimum number of CCEs to each of the one or more search space sets, or a combination thereof.
9. The method of claim 1 , wherein the determining the respective numbers of available CCEs for the one or more sets of decoding candidates comprises:
allocating the total number of available CCEs to the one or more search space sets based at least in part on an aggregation level size of decoding candidates in the one or more search space sets.
10. The method of claim 1 , wherein, for each of the one or more search space sets, the determining the applied one or more sets of decoding candidates comprises performing, for each aggregation level from a highest aggregation level to a lowest aggregation level of the each of the one or more search space sets:
identifying decoding candidates of the each aggregation level spanning a number of CCEs less than or equal to a remaining number of the total number of available CCEs;
hashing the identified decoding candidates to CCEs of the first subset of CCEs; and
including decoding candidates of a next aggregation level lower than the each aggregation level that hash to CCEs of the first subset of CCEs.
11. The method of claim 1 , wherein, for each of the one or more search space sets, the determining the applied one or more sets of decoding candidates comprises:
identifying, for each aggregation level from a highest aggregation level to a lowest aggregation level of the each of the one or more search space sets, decoding candidates of the each aggregation level spanning a number of CCEs less than or equal to a remaining number of the total number of available CCEs;
hashing the identified decoding candidates to CCEs of the first subset of CCEs; and
including decoding candidates of aggregation levels lower than a lowest aggregation level that hashed to CCEs of the first subset of CCEs.
12. The method of claim 1 , wherein the one or more sets of decoding candidates comprise one or more sets of UE-specific decoding candidates of one or more UE-specific search space sets, the method further comprising:
identifying, for the control region, a set of common decoding candidates associated with the common search space set; and
hashing the set of common decoding candidates to a second subset of CCEs of the control region, wherein the total number of available CCEs is determined based at least in part on the CCE channel estimation limitation and a number of CCEs of the second subset of CCEs.
13. The method of claim 12 , wherein the determining the applied one or more sets of decoding candidates comprises:
admitting, prior to the admitting the second subset of the one or more sets of decoding candidates, a third subset of the one or more sets of decoding candidates having hashed locations overlapping with the second subset of CCEs.
14. An apparatus for wireless communication at a base station, 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:
identify, for a control region of a control channel, one or more sets of decoding candidates associated with one or more search space sets;
determine a total number of available control channel elements (CCEs) for the one or more search space sets based at least in part on a CCE channel estimation limitation of a user equipment (UE);
determine respective numbers of available CCEs for the one or more search space sets based at least in part on the total number of available CCEs;
determine an applied one or more sets of decoding candidates by hashing a first subset of the one or more sets of decoding candidates associated with a common search space set to a first subset of CCEs of the control region based at least in part on the total number of available CCEs,
admit, to the applied one or more sets of decoding candidates, a second subset of the one or more sets of decoding candidates associated with a UE-specific search space set having hashed locations overlapping with the first subset of CCEs; and
transmit control information to the UE via the control channel over at least one of the applied one or more sets of decoding candidates of the control region.
15. The apparatus of claim 14 , wherein the instructions are further executable by the processor to cause the apparatus to:
determine a total number of available blind decodes for the one or more search space sets based at least in part on a blind decoding limitation of the UE;
determine respective numbers of available blind decodes for the one or more search space sets based at least in part on the total number of available blind decodes; and
prune the one or more sets of decoding candidates based at least in part on the respective numbers of available blind decodes for the one or more search space sets.