Synchronising Location Network Signal Timing
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Solution Overview
Problem
Existing methods for synchronizing positioning-unit devices to a reference device's timebase require prior knowledge of geometric distances, which is impractical in situations where device positions are unknown or when signal propagation paths are affected by multipath or fixed lines, compromising accuracy.
Innovation Solution
A method and apparatus that allow synchronization by calculating and adjusting signal timing differences between a reference device and a positioning-unit device, enabling synchronization without prior knowledge of geometric distances, using a process involving signal generation, interpretation, and propagation delay measurement via fixed lines or wireless transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If prior art synchronisation methods are used requiring a priori knowledge of geometric distance, then synchronisation can be achieved when positions are known, but the method becomes impractical or impossible when positions are unknown or classified
Solution Approach 1:
The patent introduces a two-way signal exchange mechanism where the positioning-unit device sends a signal to the reference device and receives a response. The reference device acts as an intermediary that reflects the signal back with embedded time information, enabling the positioning-unit device to calculate propagation delay without needing to know the geometric distance a priori
Solution Approach 2:
The reference device measures the time difference between receiving the positioning-unit device's signal and transmitting its response, then feeds back this time difference information to the positioning-unit device. This feedback loop enables automatic calculation and correction of propagation delay, eliminating the need for prior distance knowledge
2Measurement precision
If geometric distance is used to calculate propagation delay, then synchronisation accuracy can be maintained when distance is known, but accuracy is compromised when geometric distance does not represent actual propagation path
Solution Approach 1:
The system uses the actual signal propagation path itself to measure the delay, rather than relying on pre-calculated geometric distances. The reference device measures the actual time it takes for signals to travel between devices, automatically adapting to multipath effects and fixed line propagation without requiring external distance information
Solution Approach 2:
The patent changes the measurement parameter from geometric distance (a spatial parameter) to signal propagation time (a temporal parameter). This allows the system to accurately measure delays regardless of whether signals travel through air, cable, or experience multipath effects, as the actual propagation time is measured directly
Data Source
AI summary
Apparatus and methods are presented for synchronising a slave device signal to a reference timebase, in situations where the slave device lacks knowledge of the propagation delay for signals from the reference device, e.g. if the positions of one or both of the devices are unknown or classified, or the inter-device signal propagation distance is otherwise a-priori unknown. Reference signal propagation delay is determined using an exchange of signals between the devices, with each device using a differencing procedure for eliminating effects of receiver line bias and other hardware delays. In another aspect an exchange of signals between the devices is used to detect a time residual arising from an inaccurate propagation delay estimate. The synchronisation methods can be applied to a plurality of slave devices for providing a synchronised location network. In certain embodiments signals are transmitted wirelessly, while in other embodiments they are transmitted via a fixed line.