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Positioning in 5G networks
Satyam Dwivedi, Ritesh Shreevastav, Florent Munier, Johannes Nygren, Iana Siomina, Yazid Lyazidi, Deep Shrestha, Gustav Lindmark, Per Ernström, Erik Stare, Sara M. Razavi, Siva Muruganathan, Gino Masini, Åke Busin, Fredrik Gunnarsson
TL;DR
The paper describes how 3GPP Release 16 specifies 5G positioning signals, measurements, procedures, and architecture for regulatory, commercial, and industrial requirements. It presents the standardized capabilities and evaluates them in agreed 3GPP simulation scenarios, reporting accuracy from a few meters outdoors to a few decimeters indoors under stated assumptions. The results show how bandwidth, method choice, deployment, interference, and antenna elements affect positioning performance.
Problem
5G positioning must address requirements ranging from tens of meters for emergency calls to decimeter-level accuracy for indoor factory and V2X use cases.
Method
The paper presents Release 16 positioning architecture, procedures, signals, measurements, and simulations across agreed 3GPP scenarios.
Results
Simulations show a few meters of accuracy outdoors and a few decimeters indoors under the evaluated deployment and parameter assumptions.
Takeaways & Limitations
Release 16 positioning supports multiple use cases through wideband signals, new timing and angle methods, and configurable positioning resources.
Abstract
from arXiv · showhide
In this paper we describe the recent 3GPP Release 16 specification for positioning in 5G networks. It specifies positioning signals, measurements, procedures, and architecture to meet requirements from a plethora of regulatory, commercial and industrial use cases. 5G thereby significantly extends positioning capabilities compared to what was possible with LTE. The indicative positioning performance is evaluated in agreed representative 3GPP simulation scenarios, showing a 90 percentile accuracy of a few meters down to a few decimeters depending on scenarios and assumptions.
I. INTRODUCTION
Release 16 positions 5G as a vital component of digitalization by extending LTE positioning with 5G enablers and specifying the associated methods, architecture, procedures, signals, and measurements. The paper presents these capabilities and demonstrates their positioning potential under stated assumptions.
- 5G positioning is presented as a vital step because position information is central to digitalization.
- Release 16 extends LTE positioning with wideband signals, higher frequencies, multiple antennas, low latency, and flexible architecture.
- The paper presents Release 16 positioning methods, architecture, procedures, signals, and measurements.
- 5G positioning requirements span tens of meters for emergency calls to a few decimeters indoors and one decimeter for V2X use cases.
- Full positioning potential requires UE and network cooperation, although specification elements remain useful when cooperation is limited.
II. POSITIONING ARCHITECTURE AND SIGNALING
Release 16 adapts the 4G positioning architecture to 5G Core Network entities and introduces new positioning methods using timing and antenna-angle measurements. It also supports broadcast or on-demand positioning assistance data, including enhanced GNSS-RTK atmospheric-delay models.
- The 5G positioning architecture derives from 4G while adding modifications for new logical nodes in the 5G Core Network.
- Multi-RTT, DL-AoD, and UL-AoA introduce timing- and angle-based positioning methods for 5G NR.
- Multi-RTT is robust against network time-synchronization errors, while angle-based methods are more relevant with mmWave and multiple antennas.
- For angle-based positioning, the LMF estimates UE location from AoD or AoA measurements together with TRP coordinates and beam configuration details.
- Release 16 supports broadcast and on-demand positioning assistance data, and enhanced GNSS-RTK models compensate for atmospheric delays.
III. POSITIONING SPECIFIC SIGNALS
NR positioning adds dedicated DL-PRS and UL-SRS reference signals while also reusing CSI-RS and SSB signals for enhanced cell ID positioning. These signals provide positioning-specific resources alongside existing radio-resource-management signals.
- Figure 2 illustrates within-slot configurations for DL-PRS and UL-SRS positioning signals.
- NR supports two new positioning reference signals: DL-PRS and UL-SRS.
- CSI-RS and SSB signals used for radio resource management can also support enhanced cell ID positioning.
A. Downlink Positioning Reference Signal, DL-PRS
Release 16 DL-PRS provides configurable time-frequency resources, repetition, periodicity, and comb-based interference suppression. These mechanisms support denser measurements, flexible deployments, and improved separation of signals from multiple TRPs.
- DL-PRS configuration spans within-slot and multi-slot levels, including starting resources, gaps, periodicity, and density.
- Repeated DL-PRS resources collect more measurements, with up to 32 repetitions within a resource-set period.Repetition can use consecutive slots or configurable gaps; FR1 resource-set periods range from 4 to 10240 milliseconds.
- Comb structures and frequency shifts enable orthogonal DL-PRS signals and accurate TOA measurements despite interference from nearby TRPs.Configurable comb values are 2, 4, 6, or 12, with frequency offsets allowing N orthogonal DL-PRS signals.
- Comb-12 provides twice as many orthogonal signals as comb-6 LTE PRS, while NR PRS length can be configured down to 2 symbols.
- DL-PRS interference mitigation also includes muting individual repetitions or entire periodic occasions.
B. Uplink signal, UL-SRS for positioning
Release 16 defines positioning-specific UL-SRS resources and resource sets as configurable uplink beams, with enhanced comb patterns and multiplexing options.
- UL-SRS resources and resource sets: Positioning SRS resources represent individual beams, while resource sets group beams directed toward a given TRP.Unlike communication SRS, positioning SRS resources do not support repetition.
- Coverage features: Positioning SRS can span 1, 2, 4, 8, or 12 consecutive OFDM symbols to provide coverage for involved TRPs.
- Comb configuration: The positioning SRS comb size can be 2, 4, or 8, with patterns that sound all subcarriers across one resource.
- UE multiplexing: An initial comb offset and cyclic shift can be configured to multiplex multiple UEs.The comb offset ranges from 0 to K_TC−1.
IV. MEASUREMENTS FOR POSITIONING
Release 16 expands NR positioning measurements beyond LTE and supports their use across serving and neighboring TRPs in multiple positioning methods.
- Standardized measurements: NR standardizes RSTD, UE Rx-Tx time difference, and PRS-RSRP downlink measurements, whereas LTE PRS positioning supported only RSTD.
- Measurement reporting: Power-based measurements are reportable from −156 to −31 dBm with 1 dB resolution.
- Measurement reporting: Timing-based measurements span −985024 to 985024 Tc units with configurable resolution of 2^kTc.One Tc corresponds to 0.51 ns; k is configured differently for FR1 and FR2.
- Positioning methods: The standardized measurement set supports DL-TDOA, DL-AoD, UL-TDOA, UL-AoA, and multi-RTT positioning methods.These methods use combinations of timing, angle, and optional received-power measurements.
- Measurement requirements: Reliable positioning requires bounded measurement periods and bounded errors for reported measurements.
V. SIMULATIONS AND DISCUSSIONS
The evaluation uses agreed Release 16 3GPP scenarios and examines positioning across channel models, frequency ranges, interference conditions, and positioning methods.
- Evaluation scenarios: 5G positioning is evaluated in Urban Macro, Urban Micro, and Indoor Open Office scenarios drawn from agreed Release 16 evaluation scenarios.
- Configuration support: The NR DL-PRS configuration hierarchy structures network assistance data and lets the UE locate measurement resources unambiguously.
- Evaluation scenarios: The Indoor Open Office scenario is evaluated in both FR1 and FR2, while Urban Macro and Urban Micro are evaluated in FR1.
- Evaluation conditions: Evaluations compare conditions with and without interference.
- Positioning methods: DL-TDOA is used for Urban Macro and Urban Micro, while Indoor Open Office also evaluates multi-RTT and UL-AoA.
A. TRPs and the downlink simulation parameters
The simulations use scenario-specific transmit powers and frequencies, with FR1 at 2 GHz and FR2 at 28 GHz, alongside specified waveform and receiver assumptions.
- Transmit parameters: Downlink transmitted powers are 49, 42, and 23 dBm in the three evaluated scenarios.
- Frequency parameters: The carrier frequency is 2 GHz in FR1 and 28 GHz in FR2.
- Waveform parameters: FR1 and FR2 use subcarrier spacings of 30 kHz and 120 kHz, respectively.The simulated DL-PRS uses comb-12 across 12 symbols of a slot.
B. The UE and the uplink simulation parameters
The simulations vary radio, positioning-method, interference, antenna, and deployment conditions, with results reported for representative UE assumptions. In IOO, bandwidth, multi-RTT, deployment geometry, interference avoidance, and antenna count materially affect positioning performance.
- Simulation assumptions: UE speeds are assumed to be 60 km/h in UMa and 3 km/h in UMi and IOO, with a dual-polarized isotropical UE antenna.The receiver noise figure is assumed to be 9 dB.
- IOO observations: Larger bandwidth in FR2 results in better performance.
- IOO observations: Multi-RTT has higher accuracy than TDOA-based methods using downlink and uplink signals while relaxing network time-synchronization requirements.
- IOO observations: Positioning performance is better inside the IOO deployment’s convex-hull region than outside it, highlighting deployment importance.Maximizing the convex-hull region while deploying base stations would improve positioning performance.
- Interference and antennas: With twelve TRPs in IOO, comb-12 provides twelve orthogonal DL-PRS resources, so interference-free and interference cases show no performance difference.In UMa and UMi, multiple TRPs interfere in the interference case because twenty-one TRPs exceed the twelve orthogonal DL-PRS resources.
- Interference and antennas: 8×8 angle-based positioning uses 64 antenna elements for uplink angle-of-arrival estimation, and accuracy improves as antenna-element count increases.These evaluations depend on the stated deployment and parameter assumptions; other selections can produce better or worse accuracy.
VI. CONCLUSIONS
The paper presents standardized 3GPP Release 16 5G positioning architecture, procedures, signals, and measurements, evaluating their potential in agreed scenarios. The evaluations indicate accuracy from a few meters outdoors to a few decimeters indoors under listed assumptions.
- 3GPP Release 16 standardizes 5G positioning architecture, procedures, signals, and measurements.
- Simulation evaluations based on agreed key scenarios indicate accuracy of a few meters outdoors and a few decimeters indoors.The reported potential depends on the listed assumptions.