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5G NR fundamental terms

Let's go over new terms with 5G NR assuming you are familiar with 4G or LTE.


  • 5G: The 5th generation cellular communications. 
  • 5G NR: 5G New Radio.
  • 5GC: 5G Core Network.
  • 5QI: 5G QoS Identifier, which can be allocated to a QoS Flow.
  • AMF: Access and Mobility Management Function - It handles NAS communications and mobility. 
  • ARP: Allocation and Retention Priority - NG-RAN can allocate its resources relatively per QoS flow compared to others by using Allocation and Retention Priority IE. 
  • BA: Bandwidth Adaptation - BWP (Bandwidth Parts) is a subset of channel bandwidth and Bandwidth Adaptation would be done by configuring the UE with BWP(s) and telling the UE which of the configured BWPs is currently the active one.  
  • BWP: Bandwidth Parts - It is a subset bandwidth of the total cell bandwidth of a cell. 
  • CFRA: Contention Free Random Access - Random Access procedure when a dedicated resource is decided. It would be used for adding PSCell to PCell. 
  • CORESET: Control Resource Set.


TS 38.300 Figure 4.1-1 Overall Architecture

  • en-gNB: Variant Next Generation Node B - Node provides NR user plane and control plane protocol to the UE. It would act as Secondary Node in EN-DC. 
  • EN-DC: EUTRA-NG Dual Connectivity - It would work with eNB as a Master Node and (en-)gNB as a Secondary. This term is officially used in 3GPP Technical Specifications replacing deployment option 3 family (3/3a/3x) 3GPP Technical Report. 
  • gNB: Next Generation Node B - Node provides NR user plane and control plane protocol to the UE, and connected via the NG interface to 5GC. It would act as Secondary Node in NGEN-DC. 
  • I-RNTI: Inactive RNTI.
  • INT-RNTI: Interruption RNTI.
  • LDPC: Low Density Parity Check - It would be used to decode NR PDSCH. 
  • MCG: Master Cell Group in MR-DC - A group of serving cells associated with the Master Node (PCell - Primary Cell) and optionally one or more SCells. 
  • MN: Master Node - Radio access node to provide the control connection to the core network. It can be a MeNB (Master eNB) in EN-DC, a Mng-eNB (Master ng-eNB) in NGEN-DC, or a MgNB (Master gNB) in NE-DC or NR-DC. 
  • MICO: Mobile Initiated Connection Only.
  • MFBR: Maximum Flow Bit Rate.
  • MR-DC: Multi-Radio Dual Connectivity - Dual Connectivity between E-UTRA and NR nodes, or between two NR nodes. 
  • NCGI: NR Cell Global Identifier. 
  • NE-DC: Next Generation EUTRA Dual Connectivity. This term is officially used in 3GPP Technical Specifications replacing deployment option 4 family (4/4a) 3GPP Technical Report. 
  • NGEN-DC: NG Core compatible EN-DC - It would work with ng-eNB as a Master Node and gNB as a Secondary. This term is officially used in 3GPP Technical Specifications replacing deployment option 7 family (7/7a/7x) 3GPP Technical Report. 
  • ng-eNB: NG interface connected eNB - Node provides LTE user plane and control plane protocol to the UE, and connected via the NG interface to 5GC. It would act as Master Node in EN-DC, or Secondary in NE-DC.
  • NG Interface: Interface between gNB and 5GC. 
  • NG-RAN: Either a gNB or an ng-eNB.
  • NR: New Radio Access for 5G.
  • Numerology: One subcarrier spacing in the frequency domain. 
  • Deployment Options: Various different network deployment options were proposed in 3GPP Technical Report. The most smooth deployment path is going to be Option 3 family (3/3a/3x), and it goes to option 7 (7/7a/7x), and then it goes to option 4 (4/4a). 
  • PCell: SpCell of a master cell group.
  • PSCell: SpCell of a secondary cell group.
  • QFI: QoS Flow ID, which is marked with a 5QI. 
  • RANAC: RAN-based Notification Area Code.
  • RMSI: Remaining Minimum System Information.
  • RNA: RAN-based Notification Area.
  • RNAU: RAN-based Notification Area Update.
  • SD: Slice Differentiator.
  • SFI-RNTI: Slot Format Indication RNTI.
  • SCG: Secondary Cell Group in MR-DC - A group of serving cells associated with the Secondary Node (PSCell - Primary Secondary Cell) and optionally one or more SCells. 
  • Slot Format: Symbol DL/UL structure based on a Slot for NR.
  • SMF: Session Management Function.
  • S-NSSAI: Single Network Slice Selection Assistance Information.
  • SpCell: Primary cell of a master or secondary cell group.
  • Split bearer: A radio bearer with RLC bearers both in MCG and SCG, which share the same PDCP in common. 
  • Split SRB: A SRB between the MN and the UE with RLC bearers both in MCG and SCG, which share the same PDCP in common. 
  • SRB3: A direct SRB between the SN and the UE in EN-DC, NGEN-DC, and NR-DC. 
  • SUL: Supplementary Uplink - Uplink only frequency band defined for 5G. 
  • UPF: User Plane Function.
  • URLLC: Ultra-Reliable and Low Latency Communications.
  • Xn: Interface among gNBs.

# References

  • TS 38.300 NR and NG-RAN Overall Description
  • TS 38.413 Physical layer procedures for control - 8.2.1 PDU Session Resource Setup
  • TS 38.213 Physical layer procedures for control - 11.1.1 UE procedure for determining slot format