3GPP Release-17 — Features summary (RAN1 → RAN5)
- Venkateshu
- Nov 28
- 6 min read
1. Introduction & scope
Release-17 was intended as the first major consolidation/evolution step after Rel-16: adding new vertical and architectural capability without a full redesign. Release-17 contains both PHY-centric items (RAN1) and higher layer/procedural items (RAN2, RAN3), plus RF/test requirement updates (RAN4) and conformance/OAM items (RAN5). This article focuses on the RAN WGs (RAN1–RAN5) and practical implementation details drawn from the 3GPP work items and technical specifications.
2. RAN1 — PHY and RF enhancements (what changed & how to implement)
2.1 Major RAN1 features in Rel-17
Extended spectrum support to 71 GHz (FR2 extension) — new channel numerology, waveform/phase noise considerations, and PA/antenna implications.
Further MIMO extensions — enhancements for massive MIMO performance, support for higher order layers, and improved feedback (more advanced CQI/PMI/RI reporting and PMI compression).
NR over NTN (satellite/HAP PHY adaptations) — modifications to accommodate long RTT, Doppler, and link budget differences.
Enhanced demodulation and receiver algorithms (improved DMRS configuration options, PTRS enhancements), and improved support for high-mobility (e.g., HST, high speed trains) at mmWave.
RedCap (NR-Light) PHY requirements: narrower bandwidths, reduced SCS and RF capability sets.
2.2 Implementation details & engineering implications
2.2.1 New frequency bands (up to 71 GHz)
PHY numerology & subcarrier spacing: above 52.6 GHz systems require revisiting oscillator phase noise budgets and adjusting PTRS density and DMRS spacing. Vendors must implement flexible SCS (15 → 240 kHz or more) and ensure the digital front-end supports larger sampling rates and bandwidths. RF front-end changes include new filtering, duplexing (TDD predominates), and PA linearity for wider instantaneous bandwidths. Implementers must consult TS 38.104 and band-specific entries (ETSI/3GPP) for Tx/Rx masks and ACLR.
Impact on RFIC design: LO generation and phase noise specifications tighten; beamforming calibration and calibration procedures must be extended to support very narrow beams.
2.2.2 NTN PHY adaptations
Large RTT and Doppler handling: RAN1 added PHY timers, frame timing, and DMRS design options to handle large propagation delay and time/frequency shifts. Implementations must allow:
Flexible timing advance handling and extended window sizes.
Doppler compensation at RU/PHY layer (fractional frequency offset handling) and robust DMRS/PBCH decoding for stretched delays.
Link budget & coding: select robust MCS and extended repetitions/coverage enhancement modes; incorporate satellite-specific physical layer repeaters and hybrid ARQ timers.
2.2.3 Massive MIMO and demodulation improvements
More flexible DMRS patterns to support more layers while reducing overhead; PTRS adjustments to mitigate phase noise at high frequencies. Implementation: baseband stacks must support dynamic DMRS allocation, per-UE layer mapping, and fast DMRS reconfiguration through RRC/PDCP signaling.
Calibration and OTA testing implications: vendors must revalidate beamforming calibration and mutual coupling compensation (OTA MIMO testing remains important, some parts postponed to Rel-18).
2.2.4 RedCap (Reduced Capability devices)
PHY constraints: smaller maximum RF bandwidth (e.g., one or few contiguous RBs), reduced RF chains (e.g., single Rx/Tx), limited MIMO layers, and simplified UE processing. Implementation: gNodeB scheduler must be able to schedule RedCap devices with different SCS and BWP sizes while still maintaining coexistence with full-cap UEs (special handling in RAN1 for DMRS/PDSCH time/frequency mapping).
Interoperability: ensure RAN-side capability signaling (UE capability exchange in RRC) supports explicit RedCap capability bits; verify PDCP/SDAP frameworks for compressed headers and power-saving modes.
3. RAN2 — Protocols and procedures (MAC/RLC/PDCP/RRC)
3.1 Key RAN2 Rel-17 features
Sidelink enhancements (relay, multicast, extended V2X features).
RedCap protocol support (lightweight RRC states, power saving, reduced feature set).
QoE / slicing control enhancements and mobility handling (improved behavior for slicing and ATSSS interactions).
Enhanced positioning procedures (new measurements and reference signal usage in protocol).
3.2 Implementation impact & details
3.2.1 Sidelink (V2X, public safety)
New RRC messages and MAC/PHY multiplexing changes: RAN2 added procedures for sidelink relay (L2/L3), multicast, and group management. Implementers must:
Extend the sidelink control channel handling and HARQ management for relay nodes.
Upgrade RRC to support sidelink configuration lists, group identities, and security context distribution.
Resource allocation modes: support both scheduled and autonomous resource selection with new RRC TLV fields for grant timing and reservation windows.
3.2.2 RedCap & RRC
Reduced RRC complexity: RedCap devices may support a reduced set of RRC states and optional features (e.g., limited measurements). RAN2 specifies capability signaling and reduced set of RRC IEs; implementers must ensure the gNodeB's RRC can handle reduced-capability UEs without impacting normal UE handling.
Power saving timers and RRC Inactive: tighter integration with MAC and DRX for energy optimization — scheduler support for longer DRX cycles and fewer grant allocations.
3.2.3 Positioning and measurements
New measurement types and reporting formats were introduced in Rel-17 to improve PRS/CSI-RS use for positioning. Implementation requires change to UE measurement reporting (RRC measurement objects and reports) and to LPP/NRPPa interfaces for location servers.
4. RAN3 — Radio architecture, IAB, NTN system considerations
4.1 Key RAN3 features in Release-17
IAB enhancements — improved resource multiplexing between parent/child links, topology robustness, and routing options.
Non-Terrestrial Network (NTN) architecture — system architecture support to integrate satellite/HAP with terrestrial 5G.
Enhanced support for non-public networks (NPNs) and edge computing integration.
4.2 Implementation detail & system integration
4.2.1 IAB (Integrated Access and Backhaul)
Resource multiplexing: Rel-17 defined additional mechanisms so an IAB-node can more flexibly split resources between access (to UEs) and backhaul (to child IAB nodes) on top of existing scheduling. Implementers must:
Update the F1/Xn-like internal signaling between parent and IAB-DU/MT.
Implement robust path management and rerouting — the IAB control plane (IAB-CU) must be able to reassign donor relationships on link failure.
Topology and routing: support for semi-static routing table updates and enhanced bearer mapping; vendors need to test congestion/priority rules for backhaul vs access traffic.
4.2.2 NTN architecture
GW and NG-RAN integration: Rel-17 specified stage-2/3 architectural changes so that satellite link characteristics are supported end-to-end. Implementers must coordinate with CN (SA/CT) to support PDU session and mobility differences (e.g., longer handovers due to GEO/LEO satellite movement).
Timing and synchronization: NTN nodes often require GNSS/time distribution (or alternative time sync) and specific handling of timing advance and HARQ timers in the RAN architecture.
5. RAN4 — RF requirements, receiver performance and testing
5.1 RAN4 Rel-17 focus areas
Enhanced RF requirements for NR FR1 and FR2 (including Tx switching, high-power UE limits, transmit diversity, 1024QAM, Pi/2 BPSK options).
Receiver and RRM requirement updates (link-level and system-level demodulation requirements, CA on mmWave, and support for high-speed scenarios).
5.2 Implementation & test implications
Conformance suites and RF test vectors: vendors must update test platforms to include new modulation/combination sets and TX/RX masks per new bands. RAN4 updated UE RF requirements; RF labs should add tests for:
Tx switching transients (for carrier aggregation and multi-band active scenarios).
OTA MIMO test beds for mmWave (some elements moved to Rel-18 but baseline tests exist).
Intermodulation and coexistence tests for new FR2 band sets.
Receiver sensitivity & demodulation: revised target MCS/BLER thresholds and demod performance; SW receiver algorithms should be tuned to new PTRS/DMRS configurations.
6. RAN5 — OAM, conformance, measurement and charging
6.1 RAN5 Rel-17 contributions
UE conformance for NTN and RedCap — test item packages and procedures for device certification.
OAM enhancements for network automation and analytics (Phase-2) — more telemetry and data models for automation/closed-loop control.
Charging & statistics updates related to new slicing and NTN traffic types.
6.2 Implementation impact
Test cases & certification: device manufacturers must include NTN test profiles (long RTT, Doppler) and RedCap conformance sets. Test houses must update scripts and RF setups. RAN5 publishes test specifications and conformance packages — consult the WG deliverables for exact test item IDs.
Network telemetry: RAN5 enhancements enable richer event reporting and counters for automation systems; vendors should instrument counters in the RAN and expose them via standardized OAM interfaces (e.g., NETCONF/YANG, RESTCONF, and management APIs).
7. Cross-WG implementation considerations
7.1 Specification mapping
Architecture & protocol baseline: TS 38.300 (NR), TS 38.401 (NG-RAN), TS 38.101-2 (UE RF), TS 38.104 (RF requirements), and 3GPP Release-17 landing pages are primary normative sources for RAN WGs.
7.2 SW/hardware partitioning & backward compatibility
Feature flags: implement Rel-17 features as individually configurable capabilities — allow operators to enable/disable (NTN, RedCap, extended FR2) to maintain coexistence with legacy Rel-15/16 networks.
Scheduler/Resource manager updates: incorporate RedCap BWPs and IAB resource multiplexing policies; ensure backward compatible RRC signaling for legacy UEs.
PHY/FPGA/ASIC considerations: for FR2 > 52 GHz work, revalidate analog front end; for NTN, implement flexible timers and HARQ windows in firmware.
7.3 Interoperability & testing
Interoperability matrix: ensure CN and RAN features are validated in interop labs — NTN requires CN changes and cross-WG coordination with SA.
Test automation & conformance: follow RAN5 test item lists; include OTA MIMO, extended RF band tests, and NTN emulation.
8. Conclusions
Release-17 represents the “first wave” of 5G-Advanced enablers: a focused set of features intended to broaden 5G applicability (NTN, RedCap, extended mmWave, sidelink improvements, IAB robustness) while tightening RF/test requirements and expanding MIMO and positioning capabilities.
9. References
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