9.1.1 PDCCH assignment procedure
36.2133GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical layer proceduresRelease 17TS
The control region of each serving cell consists of a set of CCEs, numbered from 0 to 
according to Clause 6.8.1 in [3], where 
is the total number of CCEs in the control region of subframe 
.
The UE shall monitor a set of PDCCH candidates on one or more activated serving cells as configured by higher layer signalling for control information, where monitoring implies attempting to decode each of the PDCCHs in the set according to all the monitored DCI formats.
A BL/CE UE is not required to monitor PDCCH.
A UE is not required to monitor PDCCH in an MBSFN subframe with zero-size non-MBSFN region.
The set of PDCCH candidates to monitor are defined in terms of search spaces, where a search space 
at aggregation level 
is defined by a set of PDCCH candidates. For each serving cell on which PDCCH is monitored, the CCEs corresponding to PDCCH candidate m of the search space 
are given by
where
is defined below, 
. For the common search space 
. For the PDCCH UE specific search space, for the serving cell on which PDCCH is monitored, if the monitoring UE is configured with carrier indicator field then 
for 
=0 and 
for 
>0 where 
is the carrier indicator field value and 
is the reference number of PDCCH candidates for a carrier indicator field value "x", else if the monitoring UE is not configured with carrier indicator field then 
, where 
. 
is the number of PDCCH candidates to monitor in the given search space for the scheduled serving cell. If the monitoring UE is configured with higher layer parameter shortTTI, for monitoring DCI format 7-0A/7-0B/7-1A/7-1B/7-1C/7-1D/7-1E/7-1F/7-1G, 
is replaced by the corresponding element of higher layer parameter dci7-CandidatesPerAL-PDCCH. If a carrier indicator field value "x" corresponds to a LAA SCell and the monitoring UE is configured with uplink transmission on the LAA SCell, 
is the maximum number of 
over all configured DCI formats for the LAA SCell. Otherwise, 
is determined according to Table 9.1.1-1 by replacing 
with 
.
If a UE is configured with higher layer parameter cif-InSchedulingCell-r13, the carrier indicator field value corresponds to cif-InSchedulingCell-r13, otherwise, the carrier indicator field value is the same as ServCellIndex given in [11].
If a UE is configured with a LAA SCell for UL transmissions, and if the UE is configured with higher layer parameter cif-InSchedulingCell-r14 for the LAA SCell, the carrier indicator field value in PDCCH scheduling PUSCH corresponds to cif-InSchedulingCell-r14, otherwise, the carrier indicator field value is the same as ServCellIndex given in [11].
The UE shall monitor one common search space in every non-DRX subframe at each of the aggregation levels 4 and 8 on the primary cell.
A UE shall monitor common search space on a cell to decode the PDCCHs necessary to receive MBMS on that cell when configured by higher layers. In addition to applying the procedures described in this Clause for determining PDCCH assignment for non-MBSFN subframes on a MBMS-dedicated cell to receive MBMS on that cell when configured by higher layers, the UE shall also monitor a common search space 
at aggregation level 
with a single PDCCH candidate 
and 
set to 0.
If a UE is not configured for EPDCCH monitoring, and if the UE is not configured with a carrier indicator field, then the UE shall monitor one PDCCH UE-specific search space at each of the aggregation levels 1, 2, 4, 8 on each activated serving cell in every non-DRX subframe.
If a UE is not configured for EPDCCH monitoring, and if the UE is configured with a carrier indicator field, then the UE shall monitor one or more UE-specific search spaces at each of the aggregation levels 1, 2, 4, 8 on one or more activated serving cells as configured by higher layer signalling in every non-DRX subframe.
If a UE is configured for EPDCCH monitoring on a serving cell, and if that serving cell is activated, and if the UE is not configured with a carrier indicator field, then the UE shall monitor one PDCCH UE-specific search space at each of the aggregation levels 1, 2, 4, 8 on that serving cell in all non-DRX subframes where EPDCCH is not monitored on that serving cell.
If a UE is configured for EPDCCH monitoring on a serving cell, and if that serving cell is activated, and if the UE is configured with a carrier indicator field, then the UE shall monitor one or more PDCCH UE-specific search spaces at each of the aggregation levels 1, 2, 4, 8 on that serving cell as configured by higher layer signalling in all non-DRX subframes where EPDCCH is not monitored on that serving cell.
A UE is not expected to monitor PDCCH candidates with DCI format 0/1/1A/2/2A/2B/2C/2D mapped onto the UE-specific search space, and with the CRC scrambled by the SPS C-RNTI, when the UE is configured with higher layer parameter shortProcessingTime.
A UE is not expected to monitor PDCCH candidates with DCI format 7-0A/7-0B/7-1A/7-1B/7-1C/7-1D/7-1E/7-1F/7-1G over more than
– 28 CCEs on a serving cell if the higher layer parameter dl-STTI-Length is set to ‘subslot’.
– 32 CCEs on a serving cell if the higher layer parameter dl-STTI-Length is set to ‘slot’.
A UE is not expected to be configured to monitor more than
– 6 PDCCH candidates with DCI format 7-0A/7-0B/7-1A/7-1B/7-1C/7-1D/7-1E/7-1F/7-1G on a service cell in a subslot if the higher layer parameter dl-STTI-Length is set to ‘subslot’
– 12 PDCCH candidates with DCI format 7-0A/7-0B/7-1A/7-1B/7-1C/7-1D/7-1E/7-1F/7-1G on a serving cell in a slot if the higher layer parameter dl-STTI-Length is set to ‘slot’.
The UE is not expected to be configured to monitor PDCCH corresponding to DCI format 7-0A/7-0B /7-1A/7-1B/7-1C/7-1D/7-1E/7-1F/7-1G with carrier indicator field in a given serving cell.
A UE configured with higher layer parameter shortTTI for a serving cell is not required to monitor PDCCH for the serving cell on any other serving cell.
The UE is not expected to be configured to monitor PDCCH corresponding to DCI format 7-0A/7-0B /7-1A/7-1B/7-1C/7-1D/7-1E/7-1F/7-1G when CFI value is 3 and 
.
The common and PDCCH UE-specific search spaces on the primary cell may overlap. If the UE is configured with higher layer parameter shortProcessingTime, a PDCCH with DCI format 0/1A detected in the overlap shall be considered by the UE as having been received in the PDCCH common search space.
A UE configured with the carrier indicator field associated with monitoring PDCCH on serving cell c shall monitor PDCCH configured with carrier indicator field and with CRC scrambled by C-RNTI in the PDCCH UE specific search space of serving cell c.
A UE configured with the carrier indicator field associated with monitoring PDCCH on the primary cell shall monitor PDCCH configured with carrier indicator field and with CRC scrambled by SPS C-RNTI or UL-SPS-V-RNTI in the PDCCH UE specific search space of the primary cell.
The UE shall monitor the common search space for PDCCH without carrier indicator field.
For the serving cell on which PDCCH is monitored, if the UE is not configured with a carrier indicator field, it shall monitor the PDCCH UE specific search space for PDCCH without carrier indicator field, if the UE is configured with a carrier indicator field it shall monitor the PDCCH UE specific search space for PDCCH with carrier indicator field.
If the UE is not configured with a LAA Scell, the UE is not expected to monitor the PDCCH of a secondary cell if it is configured to monitor PDCCH with carrier indicator field corresponding to that secondary cell in another serving cell.
If the UE is configured with a LAA Scell, the UE is not expected to monitor the PDCCH UE specific space of the LAA SCell if it is configured to monitor PDCCH with carrier indicator field corresponding to that LAA Scell in another serving cell,
– where the UE is not expected to be configured to monitor PDCCH with carrier indicator field in an LAA Scell;
– where the UE is not expected to be scheduled with PDSCH starting in the second slot in a subframe in an LAA Scell if the UE is configured to monitor PDCCH with carrier indicator field corresponding to that LAA Scell in another serving cell.
For the serving cell on which PDCCH is monitored, the UE shall monitor PDCCH candidates at least for the same serving cell.
A UE configured to monitor PDCCH candidates with CRC scrambled by C-RNTI, SPS C-RNTI or UL-SPS-V-RNTI with a common payload size and with the same first CCE index 
(as described in Clause 10.1) but with different sets of DCI information fields as defined in [4] in the
– common search space
– PDCCH UE specific search space
on the primary cell shall assume that for the PDCCH candidates with CRC scrambled by C-RNTI, SPS C-RNTI or UL-SPS-V-RNTI,
if the UE is configured with the carrier indicator field associated with monitoring the PDCCH on the primary cell, only the PDCCH in the common search space is transmitted by the primary cell;
otherwise, only the PDCCH in the UE specific search space is transmitted by the primary cell.
A UE configured to monitor PDCCH candidates in a given serving cell with a given DCI format size with CIF, and CRC scrambled by C- RNTI, where the PDCCH candidates may have one or more possible values of CIF for the given DCI format size, shall assume that a PDCCH candidate with the given DCI format size may be transmitted in the given serving cell in any PDCCH UE specific search space corresponding to any of the possible values of CIF for the given DCI format size.
If a serving cell is a LAA Scell, and if the higher layer parameter subframeStartPosition for the Scell indicates ‘s07’,
– The UE monitors PDCCH UE-specific search space candidates on the Scell in both the first and second slots of a subframe, and the aggregation levels defining the search spaces are listed in Table 9.1.1-1A;
otherwise,
– The aggregation levels defining the search spaces are listed in Table 9.1.1-1.
If a serving cell is a LAA Scell, the UE may receive PDCCH with DCI CRC scrambled by CC-RNTI as described in Clause 13A on the LAA Scell.
The DCI formats that the UE shall monitor depend on the configured transmission mode per each serving cell as defined in Clause 7.1.
If a UE is configured with higher layer parameter skipMonitoringDCI-format0-1A for a serving cell, the UE is not required to monitor the PDCCH with DCI Format 0/1A in the UE specific search space for that serving cell.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured with higher layer parameter skipMonitoringDCI-format0A for the LAA SCell, the UE is not required to monitor the PDCCH with DCI Format 0A in the UE specific search space for the LAA SCell.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured in transmission mode 2 and if the UE is configured with higher layer parameter skipMonitoringDCI-format4A for the LAA SCell, the UE is not required to monitor the PDCCH with DCI Format 4A in the UE specific search space for the LAA SCell.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured with higher layer parameter enableMonitoringDCI-format0B for the LAA SCell, the UE is required to monitor the PDCCH with DCI Format 0B in the UE specific search space for the LAA SCell.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured in transmission mode 2 and if the UE is configured with higher layer parameter enableMonitoringDCI-format4B for the LAA SCell, the UE is required to monitor the PDCCH with DCI Format 4B in the UE specific search space for the LAA SCell.
If a UE is not configured for PUSCH/PUCCH transmission for at least one TDD serving cell, the UE is not expected to monitor PDCCH on serving cell 
if the PDCCH overlaps in time with SRS transmission (including any interruption due to uplink or downlink RF retuning time [10]) on TDD serving cell 
not configured for PUSCH/PUCCH transmission, and if the UE is not capable of simultaneous reception and transmission on serving cell 
and serving cell 
.
If a UE is configured with higher layer parameter pdcch-candidateReductions for a UE specific search space at aggregation level L for a serving cell, the corresponding number of PDCCH candidates is given by 
, where the value of 
is determined according to Table 9.1.1-2 and 
is determined according to Table 9.1.1-1 by replacing 
with 
.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured with higher layer parameter pdcch-candidateReductions-Format0A for a UE specific search space at aggregation level L for the LAA SCell, the corresponding number of PDCCH candidates for DCI format 0A is given by 
, where the value of 
is determined according to Table 9.1.1-2 and 
is determined according to Table 9.1.1-1 by replacing 
with 
.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured with higher layer parameter pdcch-candidateReductions-Format0B-4A-4B-AL1-2 for a UE specific search space of the first and second aggregation level for the LAA SCell, the corresponding number of PDCCH candidates for DCI format 0B/4A/4B is given by 
, where the value of 
is determined according to Table 9.1.1-2 and 
is determined according to Table 9.1.1-1 by replacing 
with 
.
If a UE is configured with a LAA SCell for UL transmissions and if the UE is configured with higher layer parameter pdcch-candidateReductions-Format0B-4A-4B-AL3-4 for a UE specific search space of the third and fourth aggregation level for the LAA SCell, the corresponding number of PDCCH candidates for DCI format 0B/4A/4B is given by 
, where the value of 
is determined according to Table 9.1.1-3 and 
is determined according to Table 9.1.1-1 by replacing 
with 
.
Table 9.1.1-1: PDCCH candidates monitored by a UE
|
Search space |
Number of PDCCH |
||
|
Type |
Aggregation level |
Size [in CCEs] |
|
|
UE-specific |
1 |
6 |
6 |
|
2 |
12 |
6 |
|
|
4 |
8 |
2 |
|
|
8 |
16 |
2 |
|
|
Common |
4 |
16 |
4 |
|
8 |
16 |
2 |
|
Note: the Size [in CCEs] is given assuming 
=1
Table 9.1.1-1A: PDCCH UE-specific search space candidates monitored by a UE on LAA Scell
|
Search space |
Number of PDCCH |
Number of PDCCH |
||
|
Type |
Aggregation level |
Size [in CCEs] |
||
|
UE-specific |
1 |
6 |
6 |
6 |
|
2 |
12 |
6 |
6 |
|
|
4 |
8 |
2 |
2 |
|
|
8 |
16 |
2 |
2 |
|
Note: the Size [in CCEs] is given assuming 
=1
Table 9.1.1-2: Scaling factor for PDCCH candidates reduction
|
pdcch-candidateReductions |
Value of |
|
0 |
0 |
|
1 |
0.33 |
|
2 |
0.66 |
|
3 |
1 |
Table 9.1.1-3: Scaling factor for PDCCH candidates reduction
|
pdcch-candidateReductions |
Value of |
|
0 |
0 |
|
1 |
0.5 |
|
2 |
1 |
|
3 |
1.5 |
For the common search spaces, 
is set to 0 for the two aggregation levels 
and 
.
For the UE-specific search space 
at aggregation level
, the variable 
is defined by
where 
, 
, 
and 
, 
is the slot number within a radio frame.
The RNTI value used for 
is defined in Clause 7.1 in downlink and Clause 8 in uplink.