5G/NR  -  NR Light/RedCap  





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 RedCap

Followings are some of the highlights of Redcap.

  • Designed for simplified / low cost device==> Same goal as LTE counterpart
  • Narrower bandwidth comparing to regular NR use case (eMBB), but narrowband here means up to 20 Mhz in sub-7 Ghz and 100 Mbps in mmWave==> Even though it is called narrow band, it is already same as the max bandwidth of single carrier LTE.
  • Low power is not the scope of RedCap==> This is different from LTE counter part. It may reduce some power due to narrow bandwidth, but there is no RedCap specific power saving technique.
  • Half Duplex (optional)==> RedCap would support ordinary FDD (full duplex FDD) and TDD, but it can support Half Duplex FDD
  • a single transmit antenna,
  • a single receive antenna, with 2 antennas being optional,
  • lower-order modulation, with 256-QAM being optional

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

  • SIB elements decaring the support of RedCap on gNB (e.g, SIB1, SIB4)
  • RRC-UE Capability Information : UE is supposed to inform its capability of RedCap support
  • RRC Reconfiguration : gNB may configure RedCap (e.g, RLC, PDCP configuration)
  • MAC CE : A few additional MAC CE elements for RedCap operation

LTE vs NR in terms of Reduced Capability

There 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

  • In terms of peak data rate, the 5G Rel-17 RedCap sits in the middle, with a peak data rate requirement that is an improvement over the 4G LTE-M and NB-IoT, but below the higher end of the LTE and  Legacy NR. This positioning reflects its role as a compromise solution targeting mid-range IoT and industrial use cases.
  • Rel-17 RedCap and Rel-18 RedCap represent two iterations of Reduced Capability devices, suggesting ongoing development and improvements within the 5G RedCap category.

Legacy 5G vs 5G RedCap in terms of Key KPI

The 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

  • High Data Rate: eMBB leads significantly, with RedCap following at a lower level.
  • Low Latency: URLLC has the highest performance, while RedCap offers moderate low latency capabilities.
  • Low Cost and Long Battery Life: mMTC shows the greatest strength, suggesting it's optimized for cost efficiency and battery life. RedCap again has moderate performance, indicating it is designed to be cost-effective while still delivering reasonable data rates and latency.
  • Balance of Attributes: RedCap does not lead in any specific category but provides a balance, which can be ideal for applications that need moderate performance across the board rather than excelling in just one aspect.


UE Capability

UE 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

   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

supportOf16DRB-RedCap-r17 :Indicates whether the RedCap UE supports 16 DRBs. This capability is only applicable for RedCap UEs.

supportOfRedCap-r17 : Indicates that the UE is a RedCap UE with comprised of at least the following functional


    - 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


    - 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


    - 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.

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

SIB1-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

   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



3GPP Reference

  • RP-190831 : Key directions for Release 17 (Nokia)
  • RP-190844 : NR-Lite for Rel-17 Qualcomm views (Qualcomm)
  • RP-191047 : NR-Lite for Industrial Sensors and Wearables (Ericsson)
  • RP-191175 : Motivation for NR-lite: IoT over NR (SamSung)