5G
5G NR
5G New Radio
Rel-15 (2018)Rel-16 (2020)Rel-17 (2022)
Overview
5G New Radio (NR) is the radio access technology standardized from Release 15 onward, designed to support three broad service classes: enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). NR introduces a flexible OFDM numerology, operation across both sub-6 GHz (FR1) and mmWave (FR2) spectrum, and a service-based 5G Core (5GC).
NR can be deployed non-standalone (NSA), anchored by an LTE eNodeB and EPC via EN-DC, or standalone (SA), where the gNodeB connects directly to the 5GC. The gNodeB architecture supports a CU/DU functional split over the F1 interface, enabling centralized baseband processing.
Key Features
- Scalable OFDM numerology (15/30/60/120/240 kHz subcarrier spacing) for diverse latency/coverage needs
- Flexible slot structure with mini-slots for low-latency URLLC scheduling
- Massive MIMO and beamforming, especially critical for FR2 mmWave coverage
- Bandwidth Parts (BWP) enabling UE power saving and mixed-numerology operation
- Network slicing support end-to-end via the 5GC service-based architecture
- Native support for both NSA (EN-DC) and SA deployment architectures
Network Architecture
NG-RAN consists of gNodeBs (and, in NSA, ng-eNodeBs) connected to the 5GC over NG, and to each other over Xn. A gNodeB may be split into a Central Unit (CU) and one or more Distributed Units (DU), communicating over F1.
| Component | Full Name | Function |
|---|---|---|
| gNodeB | Next Generation Node B | NR radio resource management, scheduling, mobility, CU/DU split |
| AMF | Access and Mobility Management Function | Registration, connection/mobility management, NAS termination |
| SMF | Session Management Function | PDU session establishment, IP allocation, UPF selection |
| UPF | User Plane Function | Packet routing/forwarding, QoS enforcement, PFCP-controlled |
| UDM | Unified Data Management | Subscriber data and credential generation |
| PCF | Policy Control Function | QoS and charging policy rules |
Physical Layer
| Parameter | Value |
|---|---|
| Waveform | CP-OFDM (DL and UL), DFT-s-OFDM optional for UL coverage |
| Subcarrier spacing | 15, 30, 60 kHz (FR1); 60, 120, 240 kHz (FR2) |
| Max channel bandwidth | 100 MHz (FR1) / 400 MHz (FR2) per component carrier |
| Modulation | QPSK, 16-QAM, 64-QAM, 256-QAM |
| MIMO | Up to 8 layers DL (single-user), massive MIMO with up to 64 antenna ports |
| Channel coding | LDPC (data channels), Polar codes (control channels) |
Frequency Bands
FR1 Bands (sub-6 GHz, selected)
| Band | Frequency Range | Duplex | Region |
|---|---|---|---|
| n1 | 1920–1980 / 2110–2170 MHz | FDD | Global (2100 MHz) |
| n41 | 2496–2690 MHz | TDD | North America / APAC |
| n77 | 3300–4200 MHz | TDD | Global (C-band) |
| n78 | 3300–3800 MHz | TDD | Global (C-band) |
| n79 | 4400–5000 MHz | TDD | China / APAC |
FR2 Bands (mmWave, selected)
| Band | Frequency Range | Region |
|---|---|---|
| n257 | 26.5–29.5 GHz | Global |
| n258 | 24.25–27.5 GHz | Europe / APAC |
| n260 | 37–40 GHz | North America |
📋 Specifications:TS 38.101-1 TS 38.101-2 TS 38.104
UE Categories
| Class | Typical Peak DL | Typical Peak UL | MIMO Layers |
|---|---|---|---|
| FR1 eMBB (baseline) | ~1–2.7 Gbps | ~600 Mbps | 4 |
| FR1 with CA | ~4+ Gbps | ~900 Mbps | 4 |
| FR2 mmWave | ~4.6+ Gbps | ~1.5 Gbps | 2 |
| RedCap (Rel-17) | ~150 Mbps | ~50 Mbps | 1–2 |
Services
- Enhanced Mobile Broadband (eMBB) — high-throughput consumer and fixed-wireless access
- URLLC — ultra-reliable low-latency services for industrial automation and V2X
- mMTC — massive machine-type communications for large-scale IoT (with NB-IoT/eMTC interworking)
- Network slicing — dedicated logical networks (e.g. eMBB slice vs. URLLC slice) over shared infrastructure
- VoNR — Voice over New Radio, IMS-based voice native to standalone 5G
Security
| Layer | Algorithm Family | Purpose |
|---|---|---|
| NAS / AS ciphering | 128-NEA1/2/3 (with 256-bit extensions in later releases) | User and signaling plane confidentiality |
| NAS / AS integrity | 128-NIA1/2/3 | Signaling and user-plane integrity protection |
| Authentication | 5G-AKA or EAP-AKA' | Mutual authentication with SUCI-based subscriber identity concealment |
| Key hierarchy | K → CK/IK → KAUSF → KSEAF → KAMF → KgNB | Layered key derivation across AUSF, SEAF, AMF, and gNodeB |
Key Procedures
Registration (Attach)
- UE sends Registration Request (NAS) within an RRC Setup Complete message
- gNodeB forwards the message to the AMF as an Initial UE Message over NGAP (N2)
- AMF triggers authentication via the AUSF (5G-AKA), establishing NAS security
- AMF selects an SMF; SMF establishes a PDU session with a UPF via N4/PFCP
- AMF sends Initial Context Setup Request; gNodeB configures radio bearers via RRC Reconfiguration
- UE completes registration; a default PDU session is typically established alongside
Handover (Xn-based)
- Source gNodeB evaluates UE measurement reports against configured events
- Source gNodeB sends Handover Request to the target gNodeB over XnAP
- Target gNodeB admits resources and returns Handover Request Acknowledge
- Source gNodeB commands the UE via RRC Reconfiguration
- UE synchronizes to the target cell and confirms with RRC Reconfiguration Complete
- Target gNodeB triggers a Path Switch Request to the AMF to update the N3 user-plane path
Paging
- Downlink data or signaling arrives for a UE in RRC_IDLE or RRC_INACTIVE
- AMF (or the last-serving gNodeB, for RRC_INACTIVE) sends Paging
- gNodeBs in the relevant registration/RAN notification area broadcast Paging
- UE responds by initiating RRC connection establishment or resume
Power Saving
| Mechanism | Description | Introduced |
|---|---|---|
| Connected-mode DRX | Configurable sleep cycles while RRC_CONNECTED | Rel-15 |
| RRC_INACTIVE | Low-overhead state retaining UE context to skip full re-establishment | Rel-15 |
| BWP switching | UE falls back to a narrower/low-power bandwidth part when idle-ish | Rel-15 |
| UE Power Saving (Rel-16 PS) | Wake-up signaling and adaptive DRX ahead of paging/scheduling occasions | Rel-16 |
Interworking
| Aspect | 5G NR / 5GC | LTE / EPC |
|---|---|---|
| Core network | 5GC (service-based architecture, SBA) | EPC (point-to-point interfaces) |
| Deployment options | NSA (EN-DC via LTE anchor) or SA (direct to 5GC) | LTE-only |
| Mobility to LTE | EN-DC add/release, or inter-RAT handover N26 (5GC↔EPC) | n/a |
| Session concept | PDU Session | PDN Connection / EPS Bearer |
Extensions for Later Releases
- Rel-16: NR-U unlicensed spectrum, V2X sidelink, integrated access backhaul (IAB), industrial IoT (TSN).
- Rel-17: RedCap (NR-Light) for mid-tier IoT, NR-NTN (satellite), multicast/broadcast, small-data transmission.
- Rel-18 (5G-Advanced): AI/ML-native RAN optimization, further RedCap, XR enhancements — see the 5G-Advanced technology page.
Comparison with Previous Generations
| Aspect | LTE (4G) | 5G NR (Standalone) |
|---|---|---|
| Core network | EPC (flat, point-to-point) | 5GC (service-based architecture) |
| Peak throughput | ~300 Mbps–1 Gbps class | Multi-Gbps class, especially FR2 |
| Latency (air interface) | ~10 ms round-trip class | ~1 ms class with mini-slots (URLLC) |
| Spectrum | Sub-6 GHz only | Sub-6 GHz (FR1) and mmWave (FR2) |
| Slicing | Not natively supported | Native end-to-end network slicing |