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ControlResourceSet
What is Coreset? How CORESET work in 5G
A control resource set (CORESET) is defined as a set of REGs under given numerology (i.e., subcarrier spacing) , Particularly, in the frequency domain, a CORESET is a set of contiguous or distributed physical resource blocks (PRBs) configured using a 6-PRB granularity, within which the UE attempts to blindly decode the DCI. There is no restriction on the maximum number of segments for a given CORESET
A DCI with Aggregation Level(AL) L is mapped to physical resources in a given BWP, where necessary parameters such as frequency and time-domain resources, and scrambling sequence identity for the DMRS for the PDCCH are configured to a UE by means
of control resource set (CORESET) .
In the time domain, a CORESET spans 1, 2, or 3 contiguous OFDM symbols, and the exact duration is configured to the UE by a higher layer such as SI or UE-specific RRC depending on whether it is common CORESET or UE-specific CORESET. Compared to LTE PDCCH, the configurability of CORESETs enable efficient resource sharing between DL control and shared channels, thereby allowing for efficient Layer 1 signaling overhead management.
- A UE may be configured with up to three CORESETs (using UE-specific or common higher-layer signaling)on each of up to four BWP on a serving cell.
- Limiting the maximum number of CORESETs is beneficial for enabling more practical RRC signaling and help enable better UE dimensioning.
- Note that, the scheduling flexibility may not be impacted by limiting the maximum number of CORESETs since different monitoring occasions can be configured flexibly even with the association to the same CORESET.
- Here, it is important to note that the concept of PDCCH monitoring periodicity is defined per search space set and is not configured at the CORESET-level.
- Every configured search space with a certain monitoring periodicity (in terms of slots and starting symbols within the monitored slots) is associated with a CORESET.
The ControlResourceSet is used to configure a time/frequency control resource set (CORESET) in which to search for downlink control information
- A CORESET consists of 3 symbols in the time domain and N_RB^CORESET RBs, multiple of 6 RB in the frequency domain, it means in general CORESET are configured in units of six PRBs on a six PRB frequency grid( starting from a reference point referred to as a point A & and one, two, or three consecutive OFDM symbols in the time domain .
- Coreset might not exist in all the BWP as it is cell level configuration and UE specific Used CORESET can be allocated for PDSCH or user data.
- Each downlink Bandwidth Part can be configured with up to 3 Control Resource Sets (CORESET)
- CORESET specifies a time/frequency resources in which downlink control information (DCI) is transmitted
- CORESET might be either common or dedicated
- Common CORESET configuration is shared by multiple UEs in a cell, whereas dedicated/UE specific is defined for certain UE.
- CORESET is configurable in time and frequency domain via:
-
- PDCCHconfigcommon
- PDCCHConfigDedicated
Control Resource Set(CORESET): A CORESET is made up of multiples resource blocks (i.e, multiples of 12 REs) in the frequency domain and ‘1 or 2 or 3’ OFDM symbols in time domain.
ControlResourceSet
ControlResourceSet ::= SEQUENCE {
controlResourceSetId ControlResourceSetId,
frequencyDomainResources BIT STRING (SIZE (45)),
duration INTEGER (1..maxCoReSetDuration),
cce-REG-MappingType CHOICE {
interleaved SEQUENCE {
reg-BundleSize ENUMERATED {n2, n3, n6},
interleaverSize ENUMERATED {n2, n3, n6},
shiftIndex INTEGER(0..maxNrofPhysicalResourceBlocks-1) OPTIONAL — Need S
},
nonInterleaved NULL
},
precoderGranularity ENUMERATED {sameAsREG-bundle, allContiguousRBs},
tci-StatesPDCCH-ToAddList SEQUENCE(SIZE (1..maxNrofTCI-StatesPDCCH)) OF TCI-StateId OPTIONAL, — Cond NotSIB1-initialBWP
tci-StatesPDCCH-ToReleaseList SEQUENCE(SIZE (1..maxNrofTCI-StatesPDCCH)) OF TCI-StateId OPTIONAL, — Cond NotSIB1-initialBWP
tci-PresentInDCI ENUMERATED {enabled} OPTIONAL, — Need S
pdcch-DMRS-ScramblingID INTEGER (0..65535) OPTIONAL, — Need S
…,
[[
rb-Offset-r16 INTEGER (0..5) OPTIONAL, — Need S
tci-PresentForDCI-Format1-2-r16 INTEGER (1..3) OPTIONAL, — Need S
coresetPoolIndex-r16 INTEGER (0..1) OPTIONAL, — Need S
controlResourceSetId-v1610 ControlResourceSetId-v1610 OPTIONAL — Need S
]]
}
Control Resource set |
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ControlResourcesetID |
0 to 11 |
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frequencyDomainResources |
45 bits |
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cce-reg–MappingType |
Choice |
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Interleaved |
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nonInterleaved |
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reg-BundleSize |
2,3,6 |
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interleaveSize |
2,3,6 |
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shiftIndex |
0 to 274 |
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precoder Granularity |
SameAsREG-bundle,allContiguousRBs |
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tci-StatesPDCCH |
Seqeunce |
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tci-PresentInDCI |
enable |
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pdcch-DMRS-ScramblingID |
0 to 65535 |
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ControlResourceSet field descriptions |
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cce-REG-MappingType Mapping of Control Channel Elements (CCE) to Resource Element Groups (REG) (see TS 38.211 [16], clauses 7.3.2.2 and 7.4.1.3.2). |
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controlResourceSetId Identifies the instance of the ControlResourceSet IE. Value 0 identifies the common CORESET configured in MIB and in ServingCellConfigCommon (controlResourceSetZero) and is hence not used here in the ControlResourceSet IE. Other values identify CORESETs configured by dedicated signalling or in SIB1. The controlResourceSetId is unique among the BWPs of a serving cell. If the field controlResourceSetId-v1610 is present, the UE shall ignore the controlResourceSetId field (without suffix). |
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coresetPoolIndex The index of the CORESET pool for this CORESET as specified in TS 38.213 [13] (clauses 9 and 10) and TS 38.214 [19] (clauses 5.1 and 6.1). If the field is absent, the UE applies the value 0. |
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duration Contiguous time duration of the CORESET in number of symbols (see TS 38.211 [16], clause 7.3.2.2). |
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frequencyDomainResources Frequency domain resources for the CORESET. Each bit corresponds a group of 6 RBs, with grouping starting from the first RB group (see TS 38.213 [13], clause 10.1) in the BWP. The first (left-most / most significant) bit corresponds to the first RB group in the BWP, and so on. A bit that is set to 1 indicates that this RB group belongs to the frequency domain resource of this CORESET. Bits corresponding to a group of RBs not fully contained in the bandwidth part within which the CORESET is configured are set to zero (see TS 38.211 [16], clause 7.3.2.2). |
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interleaverSize Interleaver-size (see TS 38.211 [16], clause 7.3.2.2). |
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pdcch-DMRS-ScramblingID PDCCH DMRS scrambling initialization (see TS 38.211 [16], clause 7.4.1.3.1). When the field is absent the UE applies the value of the physCellId configured for this serving cell. |
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precoderGranularity Precoder granularity in frequency domain (see TS 38.211 [16], clauses 7.3.2.2 and 7.4.1.3.2). |
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rb-Offset Indicates the RB level offset in units of RB from the first RB of the first 6RB group to the first RB of BWP (see 38.213 [13], clause 10.1). When the field is absent, the UE applies the value 0. |
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reg-BundleSize Resource Element Groups (REGs) can be bundled to create REG bundles. This parameter defines the size of such bundles (see TS 38.211 [16], clause 7.3.2.2). |
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shiftIndex When the field is absent the UE applies the value of the physCellIdconfigured for this serving cell (see TS 38.211 [16], clause 7.3.2.2). |
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tci-PresentInDCI This field indicates if TCI field is present or absent in DCI format 1_1. When the field is absent the UE considers the TCI to be absent/disabled. In case of cross carrier scheduling, the network sets this field to enabled for the ControlResourceSet used for cross carrier scheduling in the scheduling cell (see TS 38.214 [19], clause 5.1.5). |
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tci-PresentForDCI-Format1-2 Configures the number of bits for “Transmission configuration indicator” in DCI format 1_2. When the field is absent the UE applies the value of 0 bit for the “Transmission configuration indicator” in DCI format 1_2 (see TS 38.212, clause 7.3.1 and TS 38.214, clause 5.1.5). |
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tci-StatesPDCCH-ToAddList A subset of the TCI states defined in pdsch-Config included in the BWP-DownlinkDedicated corresponding to the serving cell and to the DL BWP to which the ControlResourceSet belong to. They are used for providing QCL relationships between the DL RS(s) in one RS Set (TCI-State) and the PDCCH DMRS ports (see TS 38.213 [13], clause 6.). The network configures at most maxNrofTCI-StatesPDCCH entries. |
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Conditional Presence |
Explanation |
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NotSIB1-initialBWP |
The field is absent in SIB1 and in the PDCCH-ConfigCommon of the initial BWP in ServingCellConfigCommon, if SIB1 is broadcasted. Otherwise, it is optionally present, Need N. |
ControlResourceSetId
The ControlResourceSetId IE concerns a short identity, used to identify a control resource set within a serving cell. The ControlResourceSetId = 0 identifies the ControlResourceSet#0 configured via PBCH (MIB) and in controlResourceSetZero (ServingCellConfigCommon). The ID space is used across the BWPs of a Serving Cell. The number of CORESETs per BWP is limited to 3 (including common and UE-specific CORESETs) in Release 15.
-- ASN1START-- TAG-CONTROLRESOURCESETID-START
ControlResourceSetId ::= INTEGER (0..maxNrofControlResourceSets-1)
ControlResourceSetId-r16 ::= INTEGER (0..maxNrofControlResourceSets-1-r16)
ControlResourceSetId-v1610 ::= INTEGER (maxNrofControlResourceSets..maxNrofControlResourceSets-1-r16)
ControlResourceSetZero
The IE ControlResourceSetZero is used to configure CORESET#0 of the initial BWP (see TS 38.213 [13], clause 13).
ControlResourceSetZero ::= INTEGER (0..15)
