PDCCH modulationV15.8.0

Toolbox: CCE to REG mapper
ParameterValue
nCCE
duration Nsymb
cce-REG-MappingType
reg-BundleSize L
interleaverSize R
nshift
CCEREG
Bundle
REG
55333435
303132
24272829
242526
43212223
181920
12151617
121314
3191011
678
00345
012
3 symbols
L=6,R=3,nshift=0

Toolbox: PDCCH signal generator
ParameternRNTInID
Value
Index3029282726252423222120191817161514131211109876543210-1
Binary00000000011111110000000000001010
cinit8323082
Input bits (0,1,...)
scrambling seq (0,1,...)
scrambled bits (0,1,...)
Modulation schemeQPSK
Modulated signal

Control-channel element (CCE)

A physical downlink control channel consists of one or more control-channel elements (CCEs) as indicated in Table 7.3.2.1-1. I.e., the aggregation level equals number of CCEs per PDCCH. Higher level means lower coding rate, is more suitable for UEs with poor channel conditions.

Table 7.3.2.1-1: Supported PDCCH aggregation levels.
Aggregation levelNumber of CCEsResource Element Groups (REG)Resource Elements (RE)
11672
2212144
4424288
8848576
1616961152

Control-resource set (CORESET)

A control-resource set consists of resource blocks in the frequency domain and symbols in the time domain.

A control-channel element consists of 6 resource-element groups (REGs) where a resource-element group equals one resource block during one OFDM symbol. Resource-element groups within a control-resource set are numbered in increasing order in a time-first manner, starting with 0 for the first OFDM symbol and the lowest-numbered resource block in the control resource set.

A UE can be configured with multiple control-resource sets. Each control-resource set is associated with one CCE-to-REG mapping only.

The CCE-to-REG mapping for a control-resource set can be interleaved or non-interleaved and is described by REG bundles:

  • REG bundle i is defined as REGs {iL, iL+1,...,iL+L-1} where L is the REG bundle size, is the number of REGs in the CORESET
  • CCE j consists of REG bundles { f(6j/L), f(6j/L+1),...,f(6j/L+6/L-1)} where f(·) is an interleaver.
    • For non-interleaved CCE-to-REG mapping, L = 6 and f(x) = x.
    • For interleaved CCE-to-REG mapping, and . The interleaver is defined bywhere R ∈ {2,3,6}.

The UE is not expected to handle configurations resulting in the quantity C not being an integer.

For a CORESET configured by the ControlResourceSet IE:

  • is given by the higher-layer parameter frequencyDomainResources;
  • is given by the higher-layer parameter duration, where is supported only if the higher-layer parameter dmrs-TypeA-Position (part of ServingCellConfigCommon) equals 3;
  • interleaved or non-interleaved mapping is given by the higher-layer parameter cce-REG-MappingType;
  • L equals 6 for non-interleaved mapping and is given by by the higher-layer parameter reg-BundleSize for interleaved mapping;
  • R is given by the higher-layer parameter interleaverSize;
  • nshift ∈ {0,1,...,274} is given by the higher-layer parameter shiftIndex if provided, otherwise ; What it means: nshift applies a cyclic shift to the interleaving pattern. The cyclic shift moves the CCE pattern upwards, with wraparound from the top to the bottom.
  • for both interleaved and non-interleaved mapping, the UE may assume
    • the same precoding being used within a REG bundle if the higher-layer parameter precoderGranularity equals sameAsREG-bundle;
    • the same precoding being used across the all resource-element groups within the set of contiguous resource blocks in the CORESET, and that no resource elements in the CORESET overlap with an SSB or LTE cell-specific reference signals as indicated by the higher-layer parameter lte-CRS-ToMatchAround, if the higher-layer parameter precoderGranularity equals allContiguousRBs.
    What it means: PDCCH and DMRS are transmitted using a single antenna port (2000). 3GPP hasn't specified the precoding for PDCCH but base station can apply precoding to this antenna port to generate a beam in the direction of the UE. The precoding is transparent to the UE. The same precoding is applied to both PDCCH and DMRS so the UE can use the DMRS to estimate the composite impact of both the precoding and the propagation channel. UE shall know the freequency selectivity of the precoding applied by the base station.
Parameter structure of ControlResourceSet
ParameterValueDescriptions
controlResourceSetId0..11coreset index, unique among the BWPs of a serving cell
frequencyDomainResourcesBIT STRING (SIZE 45)a set of resource blocks, each bit corresponds a group of 6 RBs
duration1, 2, 3contiguous time duration of the CORESET in number of symbols
cce-REG-MappingTypeCHOICE
interleavednonInterleaved
reg-BundleSize2, 3, 6-number of REGs bundled together
interleaverSize2, 3, 6
shiftIndex0..274when absent, use physCellId
precoderGranularitysameAsREG-bundle, allContiguousRBsprecoder granularity in frequency domain
tci-StatesPDCCH-ToAddListSEQUENCE(SIZE 1..64) of TCI-StateIda subset of the TCI states defined in pdsch-Config
tci-StatesPDCCH-ToReleaseListSEQUENCE(SIZE 1..64) of TCI-StateId
tci-PresentInDCIenabledfield present: TCI field is present in DL-related DCI

field absent: TCI field is absent in DL-related DCI
pdcch-DMRS-ScramblingID0..65535DM-RS scrambling sequence initialization value. When absent, use physCellId

Non-interleaved CCE mapping examples
CCEREG
5333435
303132
4272829
242526
3212223
181920
2151617
121314
191011
678
0345
012
3 symbols
CCEREG
32223
2021
1819
21617
1415
1213
11011
89
67
045
23
01
2 symbols
CCEREG
111
10
9
8
7
6
05
4
3
2
1
0
1 symbol

Interleaved CCE mapping examples
CCEREG
Bundle
REG
1111697071
666768
810636465
606162
59575859
545556
28515253
484950
107454647
424344
76394041
363738
45333435
303132
14272829
242526
93212223
181920
62151617
121314
3191011
678
00345
012
3 symbols
L=6,R=3,nshift=0
CCEREG
Bundle
REG
811697071
666768
510636465
606162
29575859
545556
108515253
484950
77454647
424344
46394041
363738
15333435
303132
94272829
242526
63212223
181920
32151617
121314
0191011
678
110345
012
3 symbols
L=6,R=3,nshift=1
CCEREG
Bundle
REG
1111697071
666768
510636465
606162
109575859
545556
48515253
484950
97454647
424344
36394041
363738
85333435
303132
24272829
242526
73212223
181920
12151617
121314
6191011
678
00345
012
3 symbols
L=6,R=6,nshift=0
CCEREG
Bundle
REG
1123697071
822666768
521636465
220606162
1119575859
818545556
517515253
216484950
1015454647
714424344
413394041
112363738
1011333435
710303132
49272829
18242526
97212223
66181920
35151617
04121314
9391011
62678
31345
00012
3 symbols
L=3,R=6,nshift=0
CCEREG
Bundle
REG
31123
22
11021
20
3919
18
1817
16
3715
14
1613
12
2511
10
049
8
237
6
025
4
213
2
001
0
1 symbol
L=2,R=6,nshift=0

For CORESET 0 configured by the ControlResourceSetZero IE:

  • are defined by clause 13 of TS 38.213
  • the UE may assume interleaved mapping
  • L = 6;
  • R = 2;
  • the UE may assume normal cyclic prefix when CORESET 0 is configured by MIB or SIB1;
  • the UE may assume the same precoding being used within a REG bundle.

Scrambling

The UE shall assume the block of bits b(0), ..., b(Mbit-1), where Mbit is the number of bits transmitted on the physical channel, is scrambled prior to modulation, resulting in a block of scrambled bits according to

where the scrambling sequence c(i) is given by scrambling. The scrambling sequence generator shall be initialized with

where

  • for a UE-specific search space as defined in clause 10 of TS 38.213, nID ∈ {0,1,...,65535} equals the higher-layer parameter pdcch-DMRS-ScramblingID if configured
  • otherwise

and where

  • nRNTI is given by the C-RNTI for a PDCCH in a UE-specific search space if the higher-layer parameter pdcch-DMRS-ScramblingID is configured, and
  • nRNTI=0 otherwise.

PDCCH modulation

The UE shall assume the block of bits to be QPSK modulated as described in modulation, resulting in a block of complex-valued modulation symbols d(0),...,d(Msymb-1).


Mapping to physical resources

The UE shall assume the block of complex-valued symbols d(0),...,d(Msymb-1) to be scaled by a factor βPDCCH and mapped to resource elements (k,l)p,μ used for the monitored PDCCH and not used for the associated PDCCH DMRS in increasing order of first k, then l. The antenna port p=2000.