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NR-Light, now officially terms as Reduced Capability (RedCap) in 3GPP NR Rel 17, is designed to function as LTE M1 /LTE NB IoT. However there are some minor differences between RedCap and LTE counter part, some difference by design and some difference due to the difference of technology between NR and LTE.
Highlights of RedCapFollowings are some of the highlights of Redcap.
This is a super simplified summary of the RedCap feature and I would not extend it too much because I found a document about overall feature and usecase of RedCap that is much better than what I might have written here : What is reduced capability (RedCap) NR and what will it achieve? For the implementation of RedCap, 3GPP release 17 added several features as listed below
LTE vs NR in terms of Reduced CapabilityThere has been LTE equivalent of RedCap which targets mid-tier IoT devices (not as much reduced capability as LTE BL/CE or NB-IoT). Following table shows nice summary and comparision between NR Light(5G RedCap) and LTE Equivalent which would not require any further explanation.
Source : 5G NR-Light (RedCap): Revolutionizing IoT - Qualcomm In terms of peak data rate requirement, 5G Redcap with different release (release 17/18) and LTE equivalent are well summarized in diagram as shown below.
Source : RedCap - expanding the 5G device ecosystem for consumers and industries - Whitepaper - Ericsson Following is short descriptions of the diagram
Legacy 5G vs 5G RedCap in terms of Key KPIThe key KPI of 5G/NR RedCap in comparision with legacy NR (eMBB, URLLC, mMTC) is well illustrated as below.
Source : RedCap - expanding the 5G device ecosystem for consumers and industries - Whitepaper - Ericsson This chart compares 5G NR RedCap against other 5G NR technologies across three axes: high data rate, low latency, and low cost/long battery life. NR RedCap aims to offer a balance among the three measured attributes, without excelling in any particular one
MAC CE
UE CapabilityUE can notiffy gNB on whether it support RedCap and which specific feature it supports via the specific IEs in UE Capability Information message as listed below.
UE-NR-Capability-v1700 ::= SEQUENCE {
...
redCapParameters-r17 RedCapParameters-r17 OPTIONAL,
...
}
RedCapParameters-r17::= SEQUENCE {
-- R1 28-1: RedCap UE
supportOfRedCap-r17 ENUMERATED {supported} OPTIONAL,
supportOf16DRB-RedCap-r17 ENUMERATED {supported} OPTIONAL
}
BandNR ::= SEQUENCE {
...
bwp-WithoutCD-SSB-OrNCD-SSB-RedCap-r17 ENUMERATED {supported} OPTIONAL,
halfDuplexFDD-TypeA-RedCap-r17 ENUMERATED {supported} OPTIONAL,
,,,
}
UERadioPagingInformation-v1700-IEs ::= SEQUENCE {
ue-RadioPagingInfo-r17 OCTET STRING (CONTAINING UE-RadioPagingInfo-r17) OPTIONAL,
inactiveStatePO-Determination-r17 ENUMERATED {supported} OPTIONAL,
numberOfRxRedCap-r17 ENUMERATED {one, two} OPTIONAL,
hd-FDDRedCap-r17 ENUMERATED {supported} OPTIONAL,
nonCriticalExtension SEQUENCE {} OPTIONAL
}
components: - Maximum FR1 RedCap UE bandwidth is 20 MHz; - Maximum FR2 RedCap UE bandwidth is 100 MHz; - Support of RedCap early indication based on Msg1, MsgA (if UE indicated support of twoStepRACH-r16) and Msg3 for random access; - Separate initial UL BWP for RedCap UEs; - It includes the configuration(s) needed for RedCap UE to perform random access - Enabling/disabling of frequency hopping for common PUCCH resources - Separate initial DL BWP for RedCap UEs; - It includes CSS/CORESET for random access - For separate initial DL BWP used for paging, CD-SSB is included - For separate initial DL BWP only used for RACH, SSB may or may not be included - For separate initial DL BWP used in connected mode as BWP#0 configuration option 1, CD-SSB is included - 1 UE-specific RRC configured DL BWP per carrier; - 1 UE-specific RRC configured UL BWP per carrier; - UE-specific RRC-configured DL BWP with CD-SSB or NCD-SSB; - NCD-SSB based measurements in RRC-configured DL BWP. A RedCap UE shall set the field to supported.
Call Setup ProcedureThere can be variations of call setup procedure between gNB(Network) and a redcap UE, but a most typical procedure can be illustrated as below. A few key points are :
Followings are breakdown of the procedure ( RedCap Supportability Announcement (SIB1):
Initial Access (Msg 1, Msg 2, Msg 3, Msg 4):
Radio Resource Control (RRC) Setup:
RRC ParametersSIB1-v1700-IEs ::= SEQUENCE { hsdn-Cell-r17 ENUMERATED {true} OPTIONAL, -- Need R uac-BarringInfo-v1700 SEQUENCE { uac-BarringInfoSetList-v1700 UAC-BarringInfoSetList-v1700 } OPTIONAL, -- Cond MINT sdt-ConfigCommon-r17 SDT-ConfigCommonSIB-r17 OPTIONAL, -- Need R redCap-ConfigCommon-r17 RedCap-ConfigCommonSIB-r17 OPTIONAL, -- Need R featurePriorities-r17 SEQUENCE { redCapPriority-r17 FeaturePriority-r17 OPTIONAL, -- Need R slicingPriority-r17 FeaturePriority-r17 OPTIONAL, -- Need R msg3-Repetitions-Priority-r17 FeaturePriority-r17 OPTIONAL, -- Need R sdt-Priority-r17 FeaturePriority-r17 OPTIONAL -- Need R } OPTIONAL, -- Need R si-SchedulingInfo-v1700 SI-SchedulingInfo-v1700 OPTIONAL, -- Need R hyperSFN-r17 BIT STRING (SIZE (10)) OPTIONAL, -- Need R eDRX-AllowedIdle-r17 ENUMERATED {true} OPTIONAL, -- Need R eDRX-AllowedInactive-r17 ENUMERATED {true} OPTIONAL, -- Cond EDRX-RC intraFreqReselectionRedCap-r17 ENUMERATED {allowed, notAllowed} OPTIONAL, -- Need S cellBarredNTN-r17 ENUMERATED {barred, notBarred} OPTIONAL, -- Need S nonCriticalExtension SEQUENCE {} OPTIONAL } RedCap-ConfigCommonSIB-r17 ::= SEQUENCE { halfDuplexRedCapAllowed-r17 ENUMERATED {true} OPTIONAL, -- Need R cellBarredRedCap-r17 SEQUENCE { cellBarredRedCap1Rx-r17 ENUMERATED {barred, notBarred}, cellBarredRedCap2Rx-r17 ENUMERATED {barred, notBarred} } OPTIONAL, -- Need R ... } SIB4 ::= SEQUENCE { interFreqCarrierFreqList InterFreqCarrierFreqList, lateNonCriticalExtension OCTET STRING OPTIONAL, ..., [[ interFreqCarrierFreqList-v1610 InterFreqCarrierFreqList-v1610 OPTIONAL -- Need R ]], [[ interFreqCarrierFreqList-v1700 InterFreqCarrierFreqList-v1700 OPTIONAL -- Need R ]] } InterFreqCarrierFreqInfo-v1700 ::= SEQUENCE { interFreqNeighHSDN-CellList-r17 InterFreqNeighHSDN-CellList-r17 OPTIONAL, -- Need R highSpeedMeasInterFreq-r17 ENUMERATED {true} OPTIONAL, -- Need R redCapAccessAllowed-r17 ENUMERATED {true} OPTIONAL, -- Need R ssb-PositionQCL-Common-r17 SSB-PositionQCL-Relation-r17 OPTIONAL, -- Cond SharedSpectrum interFreqNeighCellList-v1710 InterFreqNeighCellList-v1710 OPTIONAL -- Cond SharedSpectrum2 } PosSI-SchedulingInfo-r16 ::= SEQUENCE { posSchedulingInfoList-r16 SEQUENCE (SIZE (1..maxSI-Message)) OF PosSchedulingInfo-r16, posSI-RequestConfig-r16 SI-RequestConfig OPTIONAL, -- Cond MSG-1 posSI-RequestConfigSUL-r16 SI-RequestConfig OPTIONAL, -- Cond SUL-MSG-1 ..., [[ posSI-RequestConfig-RedCap-r17 SI-RequestConfig OPTIONAL -- Cond REDCAP-MSG-1 ]] } DownlinkConfigCommon ::= SEQUENCE { frequencyInfoDL FrequencyInfoDL OPTIONAL, -- Cond InterFreqHOAndServCellAdd initialDownlinkBWP BWP-DownlinkCommon OPTIONAL, -- Cond ServCellAdd ..., [[ initialDownlinkBWP-RedCap-r17 BWP-DownlinkCommon OPTIONAL -- Need R ]] } DownlinkConfigCommonSIB ::= SEQUENCE { frequencyInfoDL FrequencyInfoDL-SIB, initialDownlinkBWP BWP-DownlinkCommon, bcch-Config BCCH-Config, pcch-Config PCCH-Config, ..., [[ pei-Config-r17 PEI-Config-r17 OPTIONAL, -- Need R initialDownlinkBWP-RedCap-r17 BWP-DownlinkCommon OPTIONAL -- Need R ]] } FeatureCombination-r17 ::= SEQUENCE { redCap-r17 ENUMERATED {true} OPTIONAL, -- Need R smallData-r17 ENUMERATED {true} OPTIONAL, -- Need R nsag-r17 NSAG-List-r17 OPTIONAL, -- Need R msg3-Repetitions-r17 ENUMERATED {true} OPTIONAL, -- Need R spare4 ENUMERATED {true} OPTIONAL, -- Need R spare3 ENUMERATED {true} OPTIONAL, -- Need R spare2 ENUMERATED {true} OPTIONAL, -- Need R spare1 ENUMERATED {true} OPTIONAL -- Need R } PUCCH-ConfigCommon ::= SEQUENCE { pucch-ResourceCommon INTEGER (0..15) OPTIONAL, -- Cond InitialBWP-Only pucch-GroupHopping ENUMERATED { neither, enable, disable }, hoppingId INTEGER (0..1023) OPTIONAL, -- Need R p0-nominal INTEGER (-202..24) OPTIONAL, -- Need R ..., [[ nrofPRBs INTEGER (1..16) OPTIONAL, -- Need R intra-SlotFH-r17 ENUMERATED {fromLowerEdge, fromUpperEdge} OPTIONAL, -- Need R pucch-ResourceCommon-RedCap-r17 INTEGER (0..15) OPTIONAL, -- Need R additionalPRBOffset-r17 ENUMERATED {n2, n3, n4, n6, n8, n9, n10, n12}OPTIONAL--Need S ]] } SI-SchedulingInfo-v1700 ::= SEQUENCE { schedulingInfoList2-r17 SEQUENCE (SIZE (1..maxSI-Message)) OF SchedulingInfo2-r17, si-RequestConfig-RedCap-r17 SI-RequestConfig OPTIONAL -- Cond REDCAP-MSG-1 } UplinkConfigCommon-v1700 ::= SEQUENCE { initialUplinkBWP-RedCap-r17 BWP-UplinkCommon OPTIONAL -- Need R } UplinkConfigCommonSIB-v1700 ::= SEQUENCE { initialUplinkBWP-RedCap-r17 BWP-UplinkCommon OPTIONAL -- Need R } PDCP-Parameters ::= SEQUENCE { ... longSN-RedCap-r17 ENUMERATED {supported} OPTIONAL, ... } RLC-Parameters ::= SEQUENCE { am-WithShortSN ENUMERATED {supported} OPTIONAL, um-WithShortSN ENUMERATED {supported} OPTIONAL, um-WithLongSN ENUMERATED {supported} OPTIONAL, ..., [[ extendedT-PollRetransmit-r16 ENUMERATED {supported} OPTIONAL, extendedT-StatusProhibit-r16 ENUMERATED {supported} OPTIONAL ]], [[ am-WithLongSN-RedCap-r17 ENUMERATED {supported} OPTIONAL ]] } Reference
YouTube
3GPP Reference
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