Radio Ranging Synchronization Using Calibration Timing Offsets
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Solution Overview
Problem
Existing radio devices face challenges in synchronizing communications during ranging processes, particularly when not having synchronized clocks, leading to inefficiencies and unreliability in both phase-based and RTT ranging due to misalignment of frequencies and timing issues.
Innovation Solution
A method and system for synchronizing radio communications by adjusting the transmission times of unmodulated-carrier ranging signals based on actual arrival times of calibration signals, considering timing offsets to ensure reliable phase-based ranging, and optionally using time-of-flight measurements for more accurate distance estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If radio devices use predetermined nominal transmission times for calibration signals, then communication scheduling is simplified, but timing misalignment occurs due to frequency offsets and propagation delays
Solution Approach 1:
The system performs preliminary timing offset measurements during a calibration stage before the actual ranging process. The first radio device determines timing offsets by analyzing arrival times of calibration signals from the second device, then uses these pre-determined offsets to adjust transmission times in subsequent ranging stages, ensuring accurate synchronization without complex real-time adjustments
Solution Approach 2:
The system implements feedback by measuring actual arrival times of calibration signals and using these measurements to determine timing offsets. The first device receives calibration signals, measures their arrival times against expected times, calculates the timing offset, and then applies this offset to adjust future transmission times, creating a closed-loop synchronization system
2Reliability
If radio devices maintain continuous receive circuitry active, then no signal is missed, but power consumption increases
Solution Approach 1:
The system uses preliminary timing offset measurements from calibration signals to predict when the first radio device should expect to receive unmodulated carrier signals. Based on these pre-determined offsets and known transmission schedules, the device can activate its receive circuitry only during specific time windows when signals are expected to arrive, rather than keeping it continuously active
Solution Approach 2:
The system transitions from continuous receive operation to periodic receive operation, where the receive circuitry is activated only during specific time windows aligned with expected signal arrivals. The device periodically checks for signals based on the timing offsets determined during calibration, reducing power consumption while maintaining reliable reception of ranging signals
3Device complexity
If timing offsets are not compensated, then transmission scheduling is simpler, but phase-based ranging accuracy deteriorates
Solution Approach 1:
The system performs preliminary measurement of timing offsets during a calibration stage using modulated calibration signals. The first radio device determines the offset between expected and actual arrival times of these signals, then applies this pre-determined offset to adjust transmission times in subsequent phase-based ranging stages, ensuring frequency alignment without adding complexity to the overall scheduling framework
Solution Approach 2:
The system changes the timing parameter of signal transmissions based on measured timing offsets. By adjusting the transmission time parameter using the offsets determined during calibration, the system ensures that unmodulated carrier signals are transmitted at frequencies that are properly aligned, thereby maintaining measurement precision in phase-based ranging
Data Source
AI summary
A system for synchronizing communications in a radio ranging process involves transmitting calibration signals according to a predetermined schedule of nominal transmission times. Timing offsets are determined. A start time is determined for a transmission of a ranging signal. The start time is earlier than a nominal start time of the ranging signal by at least the largest timing offset. Another system for synchronization involves a radio device transmitting a calibration signal to a second radio device and receiving a calibration response signal from the second radio device. A time-of-flight value is determined in dependence on a time of departure of the calibration signal and a time of arrival of the calibration response signal. A ranging signal is transmitted at a time determined in dependence on the determined time-of-flight value. A ranging response signal is received and processed to determine a range value.