C.3 Determination of SSB and CORESET#0

38.508-13GPP5GSPart 1: Common test environmentRelease 17TSUser Equipment (UE) conformance specification

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

C.3.1 General

The requirements to be met and the principles used for determining the SSB and CORESET#0 for a PCell are:

1. The complete SSB and CORESET#0 shall be within the carrier’s channel bandwidth.

2. The SSB centre frequency (SSref) shall be on the synchronisation raster.

3. The SSB shall be kept as close as possible to the carrier’s lower edge centre frequency.

4. CORESET#0 configuration is selected using lowest number of RBs and symbols in applicable table in TS 38.213 [22], clause 13.

5. The first SSB subcarrier shall be aligned with the defined resource grid given by SCS indicated by subCarrierSpacingCommon in the MIB.

C.3.2 Determination of SSB, CORESET#0 and signalling parameters for a PCell

Calculation of SSB and CORESET#0 parameters is limited to FR1 carriers with SCS=15 kHz or SCS=30 kHz, and to FR2 carriers with SCS=60 kHz or SCS=120 kHz. CORESET#0 is required for a carrier to be used as a PCell.

The following procedure is used to determine an SSB on the synchronisation raster (GSCN) and a CORESET#0 configuration (k_SSB, Offset_RBs and OffsetToPointA) as close as possible to the carrier’s lower edge. See figure C1-1 and clause C.1 for definition of parameters referenced in the procedure.

1. Determine SSB and CORESET#0:

1a. Calculate the lower of F_SSref, F_{SSref_Min}, correspondent to SSB lowest subcarrier being at the same frequency as the carrier’s lowest subcarrier; and the higher limit of F_SSref, F_{SSref_Max}, correspondent to SSB highest subcarrier being at the same frequency as the carrier’s highest subcarrier F_{SSref_Min}

F_carrierLow = see formula for F_carrierLow in Table C.1-1

F_{SSref_Min} = F_carrierLow + CRB_size * Offset_RBs,min + BW_SSB / 2

F_{SSref_Max} = F_carrierLow + ΔF_{carrierBandwidth}– BW_SSB / 2

1b. Calculate GSCN_MIN correspondent to F_{SSref_Min} in accordance to TS 38.101-1 [7], clause 5.4.3.1 for FR1 and TS 38.101-2 [7], clause 5.4.3.1 for FR2 and select the closest valid GSCN value with GSCN >= GSCN_MIN for the carrier in according to the carrier’s synchronisation raster as specified in clause 5.4.3.3 in TS 38.101-1 [7] and TS 38.101-2 [8].

1c. Calculate the F_SSref for the selected GSCN value in step 1b in accordance to TS 38.101-1 [7], clause 5.4.3.1 for FR1 and TS 38.101-2 [7], clause 5.4.3.1 for FR2.

1d. Calculate the frequency F_{offsetToPointA}, which is the lowest subcarrier of the lowest resource block with the subcarrier spacing being a multiple of resource blocks expressed in terms of common PRB size and overlaps with the SS/PBCH block subcarrier 0 of the first resource block of the SS/PBCH block, F_SSBlow (TS 38.211 [3], clause 7.4.3.1):

F_SSBlow = F_SSref – BW_SSB / 2

F_{offsetToPointA} = CRB_size * Floor((F_SSBlow – F_carrierLow) / CRB_size) + F_carrierLow

1e. Calculate the maximum Offset_RBs value with F_CORESET0Low >= F_carrierLow:

Max_Offset_RBs = (F_{offsetToPointA} – F_carrierLow) / CRB_size

1f. Select the largest valid Offset_RBs value equal or smaller than the calculated max value, Max_Offset_RBs in step 1e within the applicable values for the carrier in TS 38.213 [4], table 13-1 to 13-10 limited to the table indexes with number of RBs and number of symbols equal to the minimum value of in the table and minimum value of for the selected .If a valid Offset_RBs value is found, then continue from step 1g.

If no valid Offset_RBs value is found, then select the next valid GSCN with F_SSref <= F_{SSref_Max} within the valid GSCN range for the carrier and repeat steps 1b to 1f.

If no valid Offset_RBs value found within the valid GSCN range then will the carrier not be possible to use as PCell and F_SSref, k_SSB, F_PointA, OffsetToCarrier and OffsetToPointA are calculated as described in clause C.3.3 and the procedure is completed.

1g. Calculate k_SSB

k_SSB = (F_SSBlow – F_{offsetToPointA}) / {15 kHz for FR1, subCarrierSpacingCommon (MIB) for FR2} (TS 38.211 [3], clause 7.4.3.1).

N = SCS_SSB / {15 kHz for FR1; subCarrierSpacingCommon (MIB) for FR2}.
k_SSB MOD N <> 0 indicates that the SSB subcarriers are not aligned with the resource grid given by the SCS indicated by subCarrierSpacingCommon in the MIB.

If k_SSB is an integer and k_SSB MOD N = 0, then continue from step 2.

If k_SSB is not an integer value or k_SSB MOD N <> 0, then select the next valid GSCN with F_SSref < F_{SSref_Max} within the valid GSCN range for the carrier and repeat steps 1b to 1g.

If N > 1 and no valid k_SSB value found within the valid GSCN range for the currently selected carrier frequency F_carrier then shift F_carrier up by ΔF_Raster for Low range; or down by ΔF_Raster for Mid, Mid-Low, Mid-High and High ranges and repeat steps 1a to 1g for a maximum shift of 3 * ΔF_Raster (see clause C.3.1, Note 1).

If no valid k_SSB value found within the valid GSCN range then will the carrier not be possible to use as PCell and F_SSref, k_SSB, F_PointA, OffsetToCarrier and OffsetToPointA are calculated as described in clause C.3.2 and the procedure is completed.

2. Determine OffsetToCarrier

Select offsetToCarrier value for the carrier in accordance to Table C.3.2-1.

Table C.3.2-1: Downlink and uplink offsetToCarrier default values for different frequency ranges

Frequency range	Downlink offsetToCarrier	Uplink offsetToCarrier
Low range	0	0
Mid range	102	504
High range	504	6
Mid-Low range	12	36
Mid-High range	24	114
Note: Different values of offsetToCarrier have been selected for Low, Mid-Low, Mid, Mid-High and High ranges to achieve enhanced test coverage of the offsetToCarrier range of values.

In case low, mid and high range are exactly the same frequency, use offsetToCarrier associated to low range.

2b. Determine F_pointA:

F_PointA = F_carrierLow – offsetToCarrier * PRB_size

3. Calculate ΔF_{OffsetCORESET-0-Carrier}:

The ΔF_{OffsetCORESET-0-Carrier} value is used to calculate the Offset Carrier CORESET#0 parameter included in the test frequency tables in sub-clauses 4.3.1 and 6.2.3.

ΔF_{OffsetCORESET-0-Carrier} = F_{offsetToPointA} – Offset_RB * CRB_size – F_carrierLow

4. Calculate signalling parameters:

IE field	Value
ssb-SubcarrierOffset	Set to the 4 least significant bits of k_SSB. For the case k_SSB > 15 the extended by an additional most significant bit encoded within PBCH as specified in TS 38.213 [22]. The IE field ssb-SubcarrierOffset is signalled in the MIB.
controlResourceSetZero	Set to the index associated with the selected Offset_RBs value in the applicable table, 13-1 to 13-10, in TS 38.213 [22]. The IE field controlResourceSetZero is signalled in the IE pdcch-ConfigSIB1 in the MIB.
absoluteFrequencySSB	Set to F_SSref expressed in ARFCN as defined in TS 38.101-1 [15] and TS 38.101-2 [39], clause 5.4.2.
absoluteFrequencyPointA	Set to F_PointA expressed in ARFCN as defined in TS 38.101-1 [15] and TS 38.101-2 [39], clause 5.4.2.
offsetToPointA	(F_{OffsetToPointA} – F_PointA) / (12{15 kHz for FR1; 60 kHz for FR2}). The IE field offsetToPointA is signalled in IE FrequencyInfoDL-SIB*.
offsetToCarrier	Set to value calculated in step 2a. The IE field offsetToCarrier is signalled in IE SCS-SpecificCarrier.

C.3.3 Determination of SSB and signalling parameters for a carrier without CORESET#0

The following procedure is used for calculation of SSB and signalling parameters for a carrier without a CORESET#0.

1. Calculate F_SSref, k_SSB and F_PointA with the SSB lowest subcarrier at the carrier’s lowest subcarrier (ΔF_{OffsetSSB-Carrier} in Figure C.1-1 = 0):

F_SSref = F_carrierLow + BW_SSB / 2

k_SSB = {31 for FR1; 15 for FR2} indicating that no CORESET#0 is present for the carrier (TS 38.213 [4], clause 13).

offsetToCarrier = target value for offsetToCarrier dependent on frequency range as specified in Table C.3.1-1.

F_PointA = FcarrierLow – offsetToCarrier * PRB_size

2. Calculate signalling parameters:

IE field	Value
ssb-SubcarrierOffset	Set to the 4 least significant bits of k_SSB. For the case k_SSB > 15 the extended by an additional most significant bit encoded within PBCH as specified in TS 38.213 [22]. The IE field ssb-SubcarrierOffset is signalled in the MIB.
controlResourceSetZero	Set to 0 indicating that no CORESET#0 exist (TS 38.213 [22], clause 13). The IE field controlResourceSetZero is signalled in the IE pdcch-ConfigSIB1 in the MIB.
searchSpaceZero	Set to 0 indicating that no CORESET#0 exist (TS 38.213 [22], clause 13). The IE field searchSpaceZero is signalled in the IE pdcch-ConfigSIB1 in the MIB.
absoluteFrequencySSB	Set to F_SSref expressed in ARFCN as defined in TS 38.101-1 [15] and TS 38.101-2 [39], clause 5.4.2.
absoluteFrequencyPointA	Set to F_PointA expressed in ARFCN as defined in TS 38.101-1 [15] and TS 38.101-2 [39], clause 5.4.2.
offsetToCarrier	Set to offsetToCarrier target value selected in step 1.