Reference Clock Shift Compensation for 5G NR Positioning Timing
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Solution Overview
Problem
5G NR positioning systems are sensitive to reference clock drift, leading to significant timing errors and decreased accuracy due to the use of higher frequencies, especially in scenarios like DL-TDOA, UL-TDOA, and multi-RTT positioning.
Innovation Solution
Implement a local procedure in terminal devices to compensate for reference clock frequency adjustments by applying frequency shifts to the local reference clock based on synchronization with access nodes, using phase-locked loops to synchronize transmission and reception timing accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher frequencies are used for positioning in 5G NR, then positioning throughput and speed are improved, but positioning accuracy deteriorates due to increased sensitivity to reference clock drift
Solution Approach 1:
The system performs preliminary frequency shift compensation calculations before positioning measurements are taken. The terminal device calculates frequency shifts based on timing advance values and applies these corrections in advance to the reference clock, preventing timing errors from accumulating during the positioning process.
Solution Approach 2:
The system implements a feedback mechanism where the terminal device monitors timing advance values from the network and uses this information to continuously adjust and compensate for frequency drift in the reference clock, maintaining synchronization and positioning accuracy over time.
2Reliability
If reference clock frequency adjustments are made to maintain synchronization, then timing synchronization is improved, but positioning accuracy deteriorates due to un补偿ed frequency shifts
Solution Approach 1:
The terminal device calculates the frequency shift amount in advance based on timing advance values received from the network, before the actual positioning measurement occurs. This preliminary calculation allows the system to pre-compensate for frequency drift, ensuring both synchronization and measurement accuracy.
Solution Approach 2:
The system dynamically changes the frequency parameter of the reference clock based on calculated shifts. By adjusting the reference clock frequency using the formula f_adjusted = f_reference × (1 - Δf/f_reference), the system maintains timing synchronization while compensating for drift-induced positioning errors.
3Measurement precision
If frequency shift compensation is applied to maintain positioning accuracy, then positioning accuracy is improved, but system complexity increases due to additional calculation and adjustment procedures
Solution Approach 1:
The terminal device autonomously performs frequency shift compensation calculations using timing advance values it already receives from the network for uplink synchronization. The system leverages existing signaling messages and internal processing capabilities, avoiding the need for additional dedicated compensation signaling or external assistance.
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
Enhances positioning accuracy by minimizing errors caused by reference clock drift, ensuring precise timing adjustments in uplink and downlink operations, particularly in challenging environments such as rural areas or with multiple antenna arrays.
Implementation Method 1
using phase-locked loops to synchronize transmission and reception timing accurately
Data Source
AI summary
According to an aspect, there is provided an apparatus for a first terminal device. The apparatus is configured to perform the following. The apparatus transmits (301) a first uplink reference signal at a first transmission time instance measured according to a local reference clock of the first terminal device. The apparatus applies (302) a frequency shift to a frequency of the local reference clock at a frequency-shift time instance measured according to the local reference clock and following the first transmission time instance. Based on the first transmission time instance, a second transmission time instance for an upcoming transmission of a second uplink reference signal, the frequency shift and the frequency-shift time instance, the apparatus calculates (303) a shift of transmission timing for the upcoming transmission. The apparatus applies (304) the shift of transmission timing to the second transmission time instance and thereafter transmits (305) the second uplink reference signal at the second time instance.