5G/NR  

 

 

 

 

How to make an SSB without SIB1 information ?

One of the key characteristics of NCD SSB would be stated as 'SSB that is not associated with SIB1' or 'SSB that does not carry information of SIB1'.  How can we make SSB like this ? All SSB includes PBCH and the PBCH carries MIB. MIB always carries IE(Information Elements) about SIB1 information (i.e, the positioning information about CORESET 0). That being said, how is it possible to make SSB not associated with SIB1.

The simple answer is to set kSSB to out of range value. More specifically, set as described in 38.38.213-chapter 13 as below.

If a UE detects a first SS/PBCH block and determines that a CORESET for Type0-PDCCH CSS set is not present, and for 24 <≤ kSSB <≤ 29 for FR1 or for 12 <≤ kSSB <≤ 13 for FR2, the UE may determine the nearest (in the corresponding frequency direction) global synchronization channel number (GSCN) of a second SS/PBCH block having a CORESET for an associated Type0-PDCCH CSS set as NGSCN + Nsize Noffset Nreference. Here NGSCN is the GSCN of the first SS/PBCH block, NGSCN = 1 in FR1 and FR2-1, NGSCN = 3 in FR2-2, and Noffset is a GSCN offset provided by Table 13-16 for FR1 and Table 13-17 for FR2. If the UE detects an SS/PBCH block and the second SS/PBCH block does not provide a CORESET for Type0-PDCCH CSS as described in 38.213- 4.1, the UE may ignore the information related to GSCN of SS/PBCH block locations for performing cell search.

If a UE detects a SS/PBCH block and determines that a CORESET for Type0-PDCCH CSS set is not present, and for kSSB = 31 for FR1 or kSSB = 15 for FR2, the UE determines that there is no SS/PBCH block having an associated Type0-PDCCH CSS set within a GSCN range [NGSCNreference − Noffset , NGSCNreference + Noffset] where NGSCNreference and Noffset are respectively determined by controlResourceSetZero and searchSpaceZero in pdcch-ConfigSIB1. If the GSCN range is [NGSCNreference, NGSCNreference] the UE determines that there is no information for a second SS/PBCH block with a CORESET for an associated Type0-PDCCH CSS set on the detected SS/PBCH block.

If a UE does not detect any SS/PBCH block providing a CORESET for Type0-PDCCH CSS set, as described in 38.213-4.1, within a time period determined by the UE, the UE may ignore the information related to GSCN of SS/PBCH locations in performing cell search.

< 38.213 - Table 13-16: Mapping between the combination of kSSB and controlResourceSetZero and searchSpaceZero in pdcch-ConfigSIB1 to NGSCNOffsetfor FR1 >

< 38.213 - Table 13-17: Mapping between the combination of kSSB and controlResourceSetZero and searchSpaceZero in pdcch-ConfigSIB1 to NGSCNOffsetfor FR2 >

UE Capability Information

UE can notiffy gNB on whether it support the capability of using NCD-SSB if availabel  via the specific IEs in UE Capability Information message as listed below. 

RedCapParameters-r17::= SEQUENCE {
   -- R1 28-1: RedCap UE
   supportOfRedCap-r17 ENUMERATED {supported} OPTIONAL,
   supportOf16DRB-RedCap-r17 ENUMERATED {supported} OPTIONAL
}

                    RedCapParameters-v1740::= SEQUENCE {
   ncd-SSB-ForRedCapInitialBWP-SDT-r17 ENUMERATED {supported} OPTIONAL
}

BandNR ::= SEQUENCE {
   bandNR FreqBandIndicatorNR,
   ...
   bwp-WithoutCD-SSB-OrNCD-SSB-RedCap-r17 ENUMERATED {supported} OPTIONAL,
   -- R1 28-3: Half-duplex FDD operation type A for RedCap UE
   halfDuplexFDD-TypeA-RedCap-r17 ENUMERATED {supported} OPTIONAL,
   -- R1 27-15b: Positioning SRS transmission in RRC_INACTIVE state configured outside initial UL BWP
   ...
}

ncd-SSB-ForRedCapInitialBWP-SDT-r17 : Indicates that the UE supports using RedCap-specific initial DL BWP associated with NCD-SSB for SDT. If absent, the UE only supports SDT in an initial DL BWP that includes the CD-SSB. UE supporting this feature shall indicate support of supportOfRedCap-r17 and ra-SDT-r17 and/or cg-SDT-r17.

bwp-WithoutCD-SSB-OrNCD-SSB-RedCap-r17 : Indicates support of RRC-configured DL BWP without CD-SSB or NCD-SSB. The UE can include this field only if the UE supports supportOfRedCap-r17.

RRC Parameters

BWP-DownlinkDedicated ::= SEQUENCE {
   pdcch-Config SetupRelease { PDCCH-Config } OPTIONAL, -- Need M
   pdsch-Config SetupRelease { PDSCH-Config } OPTIONAL, -- Need M
   sps-Config SetupRelease { SPS-Config } OPTIONAL, -- Need M
   radioLinkMonitoringConfig SetupRelease { RadioLinkMonitoringConfig } OPTIONAL, -- Need M
   ...,
   [[
   sps-ConfigToAddModList-r16 SPS-ConfigToAddModList-r16 OPTIONAL, -- Need N
   sps-ConfigToReleaseList-r16 SPS-ConfigToReleaseList-r16 OPTIONAL, -- Need N
   sps-ConfigDeactivationStateList-r16 SPS-ConfigDeactivationStateList-r16 OPTIONAL, -- Need R
   beamFailureRecoverySCellConfig-r16 SetupRelease {BeamFailureRecoveryRSConfig-r16} OPTIONAL, -- Cond SCellOnly
   sl-PDCCH-Config-r16 SetupRelease { PDCCH-Config } OPTIONAL, -- Need M
   sl-V2X-PDCCH-Config-r16 SetupRelease { PDCCH-Config } OPTIONAL -- Need M
   ]],
   [[
   preConfGapStatus-r17 BIT STRING (SIZE (maxNrofGapId-r17)) OPTIONAL, -- Cond PreConfigMG
   beamFailureRecoverySpCellConfig-r17 SetupRelease { BeamFailureRecoveryRSConfig-r16} OPTIONAL, -- Cond SpCellOnly
   harq-FeedbackEnablingforSPSactive-r17 BOOLEAN OPTIONAL, -- Need R
   cfr-ConfigMulticast-r17 SetupRelease { CFR-ConfigMulticast-r17 } OPTIONAL, -- Need M
   dl-PPW-PreConfigToAddModList-r17 DL-PPW-PreConfigToAddModList-r17 OPTIONAL, -- Need N
   dl-PPW-PreConfigToReleaseList-r17 DL-PPW-PreConfigToReleaseList-r17 OPTIONAL, -- Need N
                    nonCellDefiningSSB-r17 NonCellDefiningSSB-r17 OPTIONAL, -- Need R
   servingCellMO-r17 MeasObjectId OPTIONAL -- Cond MeasObject-NCD-SSB
]]
}

                    NonCellDefiningSSB-r17 ::= SEQUENCE {
   absoluteFrequencySSB-r17 ARFCN-ValueNR,
   ssb-Periodicity-r17 ENUMERATED { ms5, ms10, ms20, ms40, ms80, ms160, spare2, spare1 } OPTIONAL, -- Need S
   ssb-TimeOffset-r17 ENUMERATED { ms5, ms10, ms15, ms20, ms40, ms80, spare2, spare1 } OPTIONAL, -- Need S
   ...
}

nonCellDefiningSSB :  If configured, the RedCap UE operating in this BWP uses this SSB for the purposes for which it would otherwise have used the CD-SSB of the serving cell (e.g. obtaining sync, measurements, RLM). Furthermore, other parts of the BWP configuration that refer to an SSB (e.g. the "SSB" configured in the QCL-Info IE; the "ssb-Index" configured in the RadioLinkMonitoringRS; CFRA-SSB-Resource; PRACH-ResourceDedicatedBFR) refer implicitily to this NCD-SSB. The NCD-SSB has the same values for the properties (e.g., ssb-PositionsInBurst, PCI, ssb-PBCH-BlockPower) of the corresponding CD-SSB apart from the values of the properties configured in the NonCellDefiningSSB-r17 IE.

absoluteFrequencySSB  : Frequency of the NCD-SSB. The network configures this field so that the SSB is within the bandwidth of the BWP configured in BWP-DownlinkCommon.

ssb-Periodicity  : The periodicity of this NCD-SSB. The network configures only periodicities that are larger than the periodicity of serving cell's CD-SSB. If the field is absent, the UE applies the SSB periodicity of the CD-SSB (ssb-periodicityServingCell configured in ServingCellConfigCommon or ServingCellConfigCommonSIB).

ssb-TimeOffset  : The time offset between CD-SSB of the serving cell and this NCD-SSB. Value ms5 means the first burst of NCD-SSB is transmitted 5ms later than the first burst of CD-SSB transmitted after the first symbol of SFN=0 of the serving cell, value ms10 means the first burst of NCD-SSB is transmitted 10ms later than the first burst of CD-SSB transmitted after the first symbol in SFN=0 of the serving cell, and so on. If the field is absent, RedCap UE considers that the time offset between the first burst of CD-SSB transmitted in the serving cell and the first burst of this NCD-SSB transmitted is zero.

SuspendConfig ::= SEQUENCE {
   fullI-RNTI I-RNTI-Value,
   shortI-RNTI ShortI-RNTI-Value,
   ran-PagingCycle PagingCycle,
   ran-NotificationAreaInfo RAN-NotificationAreaInfo OPTIONAL, -- Need M
   t380 PeriodicRNAU-TimerValue OPTIONAL, -- Need R
   nextHopChainingCount NextHopChainingCount,
   ...,
   [[
   sl-UEIdentityRemote-r17 RNTI-Value OPTIONAL, -- Cond L2RemoteUE
   sdt-Config-r17 SetupRelease { SDT-Config-r17 } OPTIONAL, -- Need M
   srs-PosRRC-Inactive-r17 SetupRelease { SRS-PosRRC-Inactive-r17 } OPTIONAL, -- Need M
   ran-ExtendedPagingCycle-r17 ExtendedPagingCycle-r17 OPTIONAL -- Cond RANPaging
   ]],
   [[
   ncd-SSB-RedCapInitialBWP-SDT-r17 SetupRelease {NonCellDefiningSSB-r17} OPTIONAL -- Need M
   ]]
}

Reference

3GPP Reference

  • 38.300 - NR and NG-RAN Overall description
  • 38 306 - User Equipment (UE) radio access capabilities
  • 38.213 - NR;Physical layer procedures for control : 17.1 RedCap UE procedures
  • 38.331 -  NR;Radio Resource Control (RRC) : MIB, B.2 Description of BWP configuration options
  • TDocs
    • R2-2200190 : Discussions on RedCap-specific BWPs - Jan 17th – 25th January 2022
    • R2-2200287 : Open issues on early identification, camping restrictions and NCD-SSB - Jan 17th – 25th January 2022
    • R2-2200401 : BWP configuration for RedCap UE - Jan 17th – 25th January 2022
    • R2-2200554 : Identification and access restriction of RedCap UE, and NCD-SSB related issues - Jan 17th – 25th January 2022
    • R2-2200597 : Remaining issues on NCD SSB, identification and access for RedCap  - Jan 17th – 25th January 2022
    • R2-2200608 : On separate initial BWP and NCD-SSB for RedCap - Jan 17th – 25th January 2022
    • R2-2200830 : Using NCD-SSB or CSI-RS in DL BWPs for RedCap UEs  - Jan 17th – 25th January 2022
    • R2-2200862 : Discussion on use of NCD-SSB or CSI-RS in DL BWPs for RedCap UE  - Jan 17th – 25th January 2022
    • R2-2201113 : RedCap UE power-saving aspects at cell re-selection   - Jan 17th – 25th January 2022
    • R2-2201461 : Aspects related to the use of NCD-SSB   - Jan 17th – 25th January 2022
    • R2-2201732 : Summary of NCD-SSB and Initial BWP aspects  - Jan 17th – 25th January 2022
    • R2-2201738 : NCD-SSB and Initial BWP aspects - Jan 17th – 25th January 2022