RSTD Calculation for NTN Positioning Without GNSS
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Solution Overview
Problem
In non-terrestrial wireless networks (NTN), determining the location of user equipment (UE) without global navigation satellite systems (GNSS) information is challenging due to the longer delays compared to terrestrial networks, which complicates the calculation of reference signal time difference (RSTD).
Innovation Solution
The solution involves determining the RSTD in an NTN by calculating the difference between the sending and receiving times of subframes from multiple base stations, specifically considering the time differences between the sending instances and the receiving instances of position reference signals (PRS) from different base stations. This approach accounts for the longer delays in NTN systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the RSTD is defined simply as the receiving time difference in NTN systems, then the calculation is simpler, but the positioning accuracy deteriorates due to not accounting for the longer propagation delays
Solution Approach 1:
The patent changes the parameters used in RSTD calculation from simply receiving time difference to include both sending time difference and receiving time difference. By introducing additional time parameters (sending time instances, receiving time instances) and calculating both sending time difference and receiving time difference, the system compensates for the longer propagation delays in NTN while maintaining calculation feasibility through structured parameter collection and processing.
2Measurement precision
If GNSS information is used for UE location determination, then positioning accuracy is improved, but system dependency and potential unavailability in NTN environments worsen
Solution Approach 1:
The patent enables the UE to determine its own location using network-based RSTD measurements without relying on external GNSS systems. The UE measures the time differences of PRS from multiple base stations, calculates the RSTD, and determines its location independently, making the positioning service self-sufficient and adaptable to NTN environments where GNSS may be unavailable or less accurate.
Solution Approach 2:
The patent introduces network-based PRS (Position Reference Signals) as an intermediary mechanism between the base stations and the UE for location determination. Instead of directly using GNSS, the system uses network-transmitted PRS signals with known sending times and measurable receiving times as an intermediary to enable accurate positioning without direct GNSS dependency.
3Measurement precision
If the RSTD calculation accounts for longer propagation delays in NTN, then positioning accuracy is improved, but the calculation complexity and processing time increase
Solution Approach 1:
The patent performs preliminary actions by pre-configuring the UE with the necessary time measurement capabilities and having the network pre-synchronize PRS transmission timing. The network side prepares and transmits PRS with known sending time instances, and the UE is pre-configured to measure receiving time instances. This preliminary setup reduces the real-time calculation burden while maintaining accuracy in accounting for propagation delays.
Data Source
AI summary
Mechanisms are provided for a user equipment (UE) to determine a user equipment (UE) location in a non-terrestrial wireless network (NTN) based on a reference signal time difference (RSTD). A RSTD is determined based on a sending time difference and a receiving time difference, where the sending time difference is a time difference between a first sending time instance when a first subframe of a first position reference signal (PRS) is sent, and a second sending time instance when a second subframe of a second PRS is sent. In addition, the receiving time difference is a time difference between a first receiving time instance when the first subframe of the first PRS is received, and a second receiving time instance when the second subframe of the second PRS is received.