Local Fine Time Assistance for GNSS Acquisition
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Solution Overview
Problem
Weak GNSS satellite positioning signals lead to increased time-to-first-fix (TTFF) and power consumption in user equipment (UE) due to the difficulty in achieving fine-grained synchronization of local clocks with satellite clocks, especially in environments where satellite signals are weak, such as indoors.
Innovation Solution
The implementation of local fine time assistance within the UE, where the cellular system's timing is used to provide accurate timing information to the GNSS receiver, reducing the search space for satellite signal detection and improving positioning accuracy by generating a GNSS-cellular time relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE searches for GNSS satellite positioning signals without fine time assistance, then the UE can independently acquire positioning data, but the time-to-first-fix (TTFF) increases and power consumption increases
Solution Approach 1:
The invention applies preliminary action by providing fine time assistance information to the GNSS receiver before the actual positioning process begins. The fine time assistance, derived from cellular system timing, pre-synchronizes the UE's local clock with the GNSS satellite clock, allowing the receiver to start signal acquisition with already-aligned timing rather than searching from scratch. This preliminary time alignment dramatically reduces the TTFF while maintaining independent positioning capability.
Solution Approach 2:
The invention uses cellular system timing as an intermediary to transfer precise time information to the GNSS receiver. Instead of directly synchronizing with distant GNSS satellites, the UE first obtains accurate timing from the cellular network (which has its own synchronization infrastructure), then uses this cellular-derived fine time assistance to synchronize with GNSS. This intermediary approach provides a practical path to high-precision timing without requiring direct satellite lock.
2Measurement precision
If the UE searches for GNSS satellite positioning signals without fine time assistance, then the UE can independently acquire positioning data, but power consumption increases
Solution Approach 1:
By performing time synchronization preliminarily through cellular fine time assistance before initiating the computationally intensive GNSS signal search and processing, the UE avoids prolonged periods of high-power operation. The pre-aligned timing enables the receiver to quickly lock onto satellite signals, reducing the duration of active processing and thus lowering overall power consumption while maintaining positioning accuracy.
3Measurement precision
If the UE uses cellular system timing to provide fine time assistance to the GNSS receiver, then the search space for satellite signal detection is reduced and positioning accuracy is improved, but the device complexity increases
Solution Approach 1:
The invention leverages the existing cellular system timing infrastructure to serve dual purposes: maintaining cellular network synchronization and providing fine time assistance for GNSS positioning. The cellular timing resources, already present in the UE for communication purposes, are repurposed to enhance GNSS acquisition, avoiding the need for separate dedicated timing generation hardware or software modules. This multi-functional use of existing resources improves positioning accuracy without proportionally increasing device complexity.
Data Source
AI summary
A user equipment (UE) and method of providing local fine timing assistance are generally described. Prior to storing a Global Navigation Satellite System (GNSS)-cellular time relationship in the UE and, when the network is unable to provide fine timing assistance, a GNSS receiver transmits a request to a modem. The modem, in response, periodically or as scheduled transmits a pulse and pulse timing information (PTI) including a pulse transmission time (PTT) based on cellular network time. The receiver determines a GNSS-cellular time relationship and obtains a GNSS satellite positioning signal and GNSS fix using the PTI. For pulses after the initial pulse, the PTI includes a time difference between the PTT and a PTT of the preceding pulse. The receiver determines a time difference between the PTT and GNSS fix. The modem is configured to terminate pulse transmission in response to receiving a termination request from the receiver.