Unsynchronized Clock Positioning System for Accurate Time Synchronization
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Solution Overview
Problem
Current time synchronization methods in telecommunications networks, particularly for femtocells and mobile networks, face challenges in achieving accurate frequency and phase control across different cellular standards like CDMA, CDMA2000, and WiMAX, often requiring expensive GPS receivers or NTP protocols that are not cost-effective or suitable for all environments.
Innovation Solution
A method for determining relative range, velocity, clock frequency offset, and clock phase offset between devices using unsynchronized reference clocks, allowing devices to calculate these parameters by minimizing a cost function derived from equations representing phase and frequency relationships, enabling accurate time synchronization and positioning without the need for fixed infrastructure or synchronized clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS receivers are used for time synchronization, then time synchronization accuracy is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive GPS receivers with inexpensive reference clocks that can be easily manufactured and deployed. The system uses multiple low-cost devices with unsynchronized clocks instead of expensive high-precision GPS equipment, achieving the same time synchronization function at a fraction of the cost.
Solution Approach 2:
The system enables devices to self-synchronize by having each device use its own reference clock and allowing the network to calculate timing relationships through signal exchanges. This eliminates the need for external GPS infrastructure and allows devices to autonomously determine their time offsets through mutual signal measurement and cost function minimization.
2Device complexity
If NTP protocol is used for time synchronization, then device complexity is reduced, but time synchronization accuracy deteriorates
Solution Approach 1:
The system implements a feedback mechanism where devices exchange timing signals and measure phase differences, then use this feedback information to adjust their reference clocks. The cost function minimization process continuously refines the timing estimates based on measured phase and frequency offsets, achieving high accuracy through iterative correction.
Solution Approach 2:
The patent uses dynamic reference clocks that can adjust their frequency and phase based on measured offsets. Instead of static time synchronization, the system continuously adapts the timing relationships between devices by minimizing a cost function that accounts for phase and frequency variations over time.
3Measurement precision
If synchronized reference clocks are used, then time synchronization accuracy is improved, but device complexity and infrastructure requirements increase
Solution Approach 1:
Instead of synchronizing clocks before measurement, the patent inverts the approach by using unsynchronized reference clocks and calculating the timing relationships through signal exchanges. The system determines time offsets by measuring phase differences and minimizing a cost function, rather than attempting to maintain synchronized clocks throughout the process.
Solution Approach 2:
The patent introduces phase and frequency offset measurements as intermediaries that mediate between unsynchronized reference clocks. These intermediate measurements allow the system to bridge the timing gap between devices without requiring direct clock synchronization, using signal phase relationships as the mediating parameter.
4Measurement precision
If multiple reference signals are exchanged between devices, then positioning accuracy is improved, but communication overhead increases
Solution Approach 1:
The patent combines multiple measurement objectives into a single unified cost function that simultaneously optimizes for phase offset, frequency offset, and positioning accuracy. By merging these separate measurement goals into one minimization problem, the system achieves multiple objectives through a coordinated signal exchange protocol rather than separate measurement procedures.
Solution Approach 2:
The system uses more phase and frequency measurements than strictly necessary for basic positioning, intentionally gathering excessive data to improve accuracy through statistical refinement. The cost function minimization process exploits this excess information to achieve higher precision in both positioning and timing parameter estimation.
Data Source
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AI summary
This invention describes a device that is able to compute its range and time offset relative to another similar device, and thereby also a three-dimensional position, speed and time relative to other similar devices provided that at least four are present and within range. It does so by transmitting at least two signals at different frequencies and by receiving similar signals transmitted by the other devices. The signals are normally radio transmissions but they are constructed so that they are independent of the radio band used and so that they lead to cancellation of common-mode effects in the transmitter and receiver circuits. Being agnostic of the particular band being used means that the system is also applicable to optical, acoustic, sonar or other technologies. No fixed infrastructure of transmitters, receivers or local measurement units are required in order to determine the relative positions, velocities and time, and the devices do not need to be synchronised. If there are only three devices in a cluster then their relative positions and velocities in two-dimensions may be determined. If there are only two devices, the system allows the range, range velocity and time offset between them to be determined. The ranging technique may be used in wired systems in which it is desirable to obtain accurate time synchronisation between two devices that are cable connected and it also provides a measure of the cable length. The cluster of devices may comprise more than four, in which case the extra devices provide redundancy and allow the system to detect and correct for measurement errors caused by anomalous propagation of the signals in the environment. The system scales to very large networks of devices in which they work collectively each solving a part of the problem that describes the relative positions of all interconnected devices.