Shared Oscillator Frequency Control for Mobile GNSS
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Solution Overview
Problem
Integrating GNSS receivers and mobile communication devices poses challenges due to differing oscillator precision requirements, leading to positioning errors and increased call drop rates when sharing an oscillator.
Innovation Solution
A mobile communication device with a shared oscillator between the communication circuit and GNSS receiver, utilizing a decision unit to record and adjust the oscillator's frequency, ensuring synchronization with base station oscillators to maintain precise frequency output for both communication and positioning functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a shared oscillator is used between communication circuit and GNSS receiver to reduce hardware cost, then hardware cost is reduced, but positioning precision deteriorates due to frequency drift and synchronization issues
Solution Approach 1:
The system performs preliminary frequency adjustment of the shared oscillator before GNSS signal extraction. The communication circuit adjusts the oscillator frequency in advance to compensate for expected frequency drift, ensuring the GNSS receiver receives signals at the correct frequency. This preliminary action prevents positioning errors before they occur.
Solution Approach 2:
The system implements feedback mechanisms where the GNSS receiver provides frequency information back to the communication circuit. The communication circuit uses this feedback to continuously adjust the shared oscillator frequency, maintaining synchronization between the two functions. This closed-loop feedback ensures positioning precision despite using a shared, lower-cost oscillator.
2Reliability
If the communication circuit adjusts the oscillator frequency during GNSS signal extraction, then communication quality is improved, but positioning accuracy deteriorates due to frequency changes not being immediately detected by the GNSS receiver
Solution Approach 1:
The system performs preliminary frequency adjustment before GNSS signal extraction begins. The communication circuit adjusts the oscillator frequency in advance, and the GNSS receiver is notified of this adjustment. This ensures that when frequency changes are needed for communication quality, the positioning system is already prepared to handle the new frequency without losing accuracy.
Solution Approach 2:
The system introduces an intermediary notification mechanism between the communication circuit and GNSS receiver. When the communication circuit adjusts the oscillator frequency, it sends a notification signal to the GNSS receiver. This intermediary communication ensures the GNSS receiver is immediately aware of frequency changes and can adjust its processing accordingly, maintaining positioning accuracy during communication operations.
3Measurement precision
If the shared oscillator frequency is controlled to remain constant during GNSS signal extraction, then positioning accuracy is maintained, but call drop rate increases due to reduced adaptability to frequency variations
Solution Approach 1:
The system transitions from a static frequency control approach to a dynamic frequency adjustment approach. The shared oscillator frequency is continuously adjusted based on real-time communication conditions and GNSS reception status. This dynamic adaptation allows the system to maintain positioning accuracy when needed while improving communication quality and reducing call drop rates when frequency variations are beneficial.
Solution Approach 2:
The system changes the oscillator frequency parameter dynamically based on operational requirements. When GNSS signal extraction is active, the frequency is adjusted to maintain positioning accuracy. When communication operations require frequency variations, the system adapts the oscillator frequency accordingly. This parameter change strategy resolves the contradiction by making the frequency control flexible rather than fixed.
Data Source
AI summary
A mobile communication device with positioning capability is provided, including: a global navigation satellite system (GNSS) receiver; a communication circuit for generating a control signal; an oscillator shared between the communication circuit and the GNSS receiver, for providing a clock signal having a frequency value corresponding to the control signal; and a decision unit, coupled to the communication circuit and the GNSS receiver, for recording the control signal; wherein the GNSS receiver obtains the frequency value of the clock signal according to the control signal recorded in the decision unit.