Clock Frequency Determination via Radio Over Fiber Signal Conversion
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Solution Overview
Problem
Current wireless positioning systems, particularly those using ultra-wideband (UWB) and wireless cellular networks, face challenges in achieving high-precision clock synchronization due to individual differences in crystal oscillators, leading to inaccuracies in clock frequency synchronization and subsequently affecting positioning precision.
Innovation Solution
A clock frequency determining method and apparatus that utilizes a radio over fiber (RoF) device to generate a combined optical signal from two frequencies, converting it into an electrical signal, and setting a local clock frequency based on the signal frequency, ensuring high consistency and precision, with the ability to generate high-frequency clocks exceeding 63.8976 GHz, thereby improving clock synchronization precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If crystal oscillators are used in each positioning base station to generate clock frequency, then the system structure is simple and independent, but individual differences in manufacturing cause frequency errors and poor clock synchronization precision
Solution Approach 1:
An optical signal serves as an intermediary carrier to distribute a unified reference clock frequency from a central source to multiple access network devices. The optical signal travels through optical fibers to each device, where it is converted to electrical signals that synchronize the clock frequencies of all base stations, eliminating individual crystal oscillator variations while maintaining system simplicity.
Solution Approach 2:
A single reference clock source generates a unified frequency that serves all positioning base stations simultaneously through optical signal distribution. This universal reference clock replaces multiple independent crystal oscillators, ensuring consistent frequency standards across the entire system without requiring complex individual adjustment mechanisms at each base station.
2Measurement precision
If crystal oscillators with same specification are used in all positioning base stations, then manufacturing cost is controlled, but frequency errors still occur due to individual differences, affecting positioning precision
Solution Approach 1:
The optical signal acts as a mediator that carries the unified reference clock frequency from a central source to all access network devices. This intermediary transmission method ensures that all devices receive the exact same frequency reference, eliminating the reliability issues caused by individual crystal oscillator variations while maintaining cost-effectiveness.
Solution Approach 2:
The system changes the frequency reference parameter from locally-generated crystal oscillator frequencies to a centrally-distributed optical signal frequency. This parameter change ensures that all positioning base stations use the same frequency standard, improving both clock frequency consistency and positioning precision without increasing manufacturing costs.
3Measurement precision
If a unified external reference clock is used to determine local clock frequency, then clock synchronization precision and positioning accuracy are improved, but the system requires additional optical signal distribution infrastructure
Solution Approach 1:
The patent replaces the traditional electrical/electronic clock synchronization system with an optical-based reference distribution system. By using optical signals transmitted through optical fibers to carry the reference clock frequency, the system achieves higher precision while the optical infrastructure leverages existing communication fiber networks, reducing the actual added complexity.
Solution Approach 2:
The optical fiber infrastructure serves dual purposes: it distributes both data/communication signals and the reference clock frequency simultaneously. This multi-functionality means that the same physical infrastructure supports both communication and synchronization functions, minimizing the additional complexity required for high-precision positioning.
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 enhances clock synchronization precision, leading to improved positioning accuracy by ensuring consistent clock frequencies across access network devices, reducing clock drift and asynchronization, and enabling higher precision in positioning, especially in scenarios requiring high-speed movement and low latency, such as in 5G/6G indoor environments.
Implementation Method 1
converting the combined optical signal into an electrical signal
Data Source
AI summary
This application provides a clock frequency determining method and a clock frequency determining apparatus. The method includes: An access network device receives a combined optical signal from a radio over fiber RoF device, where the combined optical signal is obtained by coupling an optical signal of a first frequency and an optical signal of a second frequency; the access network device converts the combined optical signal into an electrical signal; and the access network device sets a local clock frequency based on a signal frequency of the electrical signal and a first preset rule, where the signal frequency of the electrical signal is equal to an absolute value of a frequency difference between the first frequency and the second frequency.