Passive Positioning in 5G NR Using Overheard PRS

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Solution Overview

Problem

Existing positioning methods in 5G NR face challenges in high-density areas due to messaging and bandwidth limitations, particularly with Round Trip Time (RTT) methods, and require network synchronization, which is not scalable.

Innovation Solution

The proposed solution utilizes passive positioning techniques with a plurality of stations, where a first base station transmits a Downlink Positioning Reference Signal (DL PRS) to a second base station, and the User Equipment (UE) overhears these signals. The UE computes the Time Difference of Arrival (TDOA) position using the turnaround time information and location/distance information associated with the stations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If RTT positioning methods are used in high-density areas, then positioning capability is provided, but messaging and bandwidth limitations are exceeded

Engineering Contradiction:

Improvepositioning capabilityVSAvoidmessaging and bandwidth

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts the UE response transmission function from the positioning procedure. Instead of the UE transmitting response signals that consume bandwidth, the network computes positioning based solely on downlink PRS measurements made by the UE. This removes the uplink messaging burden while preserving positioning capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The downlink PRS signals serve multiple functions: they enable positioning measurements by the UE, and they are also received and measured by other base stations for network-based positioning computations. This multi-functional use of the same signal infrastructure improves efficiency without requiring additional dedicated positioning messages.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If RTT positioning methods are used, then positioning is achieved, but network synchronization is required

Engineering Contradiction:

Improvepositioning accuracyVSAvoidnetwork synchronization

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces a location server as an intermediary that centralizes the synchronization management and positioning computation functions. The location server receives measurement data from the network and performs the positioning calculations, absorbing the synchronization complexity away from the distributed base stations and UEs.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical synchronization requirement with a computational approach. Instead of requiring precisely synchronized transmissions and receptions across the network, the system uses the UE's reception time measurements of downlink signals from multiple base stations to compute position through TDOA or similar methods, which are less sensitive to absolute synchronization.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If scalable positioning is needed in high-density environments, then bandwidth limitations must be avoided, but traditional methods require UE transmission responses

Engineering Contradiction:

ImprovescalabilityVSAvoidbandwidth consumption

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for scalable positioning in high-density environments without exceeding bandwidth limitations, as the UE does not need to transmit responses to the PRS transmissions, and it does not require network synchronization.

Implementation Method 1

The UE computes the Time Difference of Arrival (TDOA) position using the turnaround time information and location/distance information associated with the stations

Methodology Applied

Scientific EffectTime Difference of Arrival (TDOA): Time of Flight

Data Source

PatentEP4169310B1Passive positioning methods in new radio

Publication Date: 2025.04.16 QUALCOMM INC

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AI summary

Techniques are provided for passive positioning of user equipment (UE). An example method for passive positioning of a user equipment includes receiving a first positioning reference signal from a first station at a first time, receiving a second positioning reference signal from a second station at a second time, receiving a turnaround time value associated with the first positioning reference signal and the second positioning reference signal, and a distance value based on a location of the first station and a location of the second station, and determining a time difference of arrival based at least in part on the turnaround time value, the distance value, the first time, and the second time.