Oscillator Drift Compensation in Wireless Mesh Networks
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Solution Overview
Problem
Battery-powered nodes in wireless mesh networks face disconnection due to temperature-induced oscillator drift, as they cannot implement power-consuming temperature-compensated crystal oscillators (TCXOs) effectively.
Innovation Solution
A computer-implemented method where battery-powered nodes acquire calibration packets from continuously powered nodes to determine and adjust for oscillator drift, using the accurate oscillators in continuously powered devices without the need for TCXOs, thereby maintaining precise timing for data communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature-compensated crystal oscillator (TCXO) is included in each battery-powered node to compensate for oscillator drift, then the timing accuracy is improved, but the power consumption increases significantly
Solution Approach 1:
The patent introduces continuously-powered nodes as intermediaries that generate and distribute calibration packets containing accurate timing information. Battery-powered nodes use these calibration packets to compensate for their oscillator drift without needing power-consuming TCXOs. The calibration packets act as a mediator transferring timing accuracy from power-rich nodes to power-constrained nodes.
Solution Approach 2:
Instead of equipping each battery-powered node with its own expensive TCXO, the patent creates copies of the timing calibration data from continuously-powered nodes and distributes them via calibration packets. Each BPD receives and applies a copy of the drift compensation information, achieving accurate timing without duplicating the expensive hardware.
2Use of energy by moving object
If battery-powered nodes use low-frequency oscillators to maintain current time, then power consumption is reduced, but temperature-induced oscillator drift causes timing errors and potential disconnection
Solution Approach 1:
The system implements a feedback mechanism where continuously-powered nodes monitor their oscillator drift and generate calibration packets containing correction information. Battery-powered nodes receive these calibration packets and apply the corrections to their timing, creating a closed-loop system that maintains accurate timing despite using low-power oscillators.
Solution Approach 2:
Continuously-powered nodes perform preliminary calibration measurements and generate compensation values in advance, storing them in calibration packets. When battery-powered nodes need timing correction, they already have pre-computed calibration data available, eliminating the need for real-time complex calculations or continuous monitoring.
3Use of energy by moving object
If battery-powered nodes power on at precisely timed intervals to conserve power, then energy efficiency is improved, but oscillator drift causes them to power on too early or too late and miss communication intervals
Solution Approach 1:
The calibration packet mechanism provides feedback information about actual oscillator drift to battery-powered nodes. This allows them to adjust their wake-up timing based on measured drift, ensuring they power on at the correct communication intervals and maintain reliable data transmission while still conserving power.
Data Source
AI summary
A battery powered node within a wireless mesh network maintains a mapping between temperature and oscillator drift and compensates for oscillator drift based on this mapping. When the mapping includes insufficient data points to map the current temperature to an oscillator drift value, the battery powered node requests calibration packets from an adjacent upstream node in the network. The adjacent node transmits two calibration packets with a transmit time delta and also indicates this time delta in the first calibration packet. The battery powered node receives the two calibration packets and measures the receive time delta. The battery powered node compares the transmit time delta to the receive time delta to determine oscillator drift compared to an oscillator in the adjacent node. The battery powered node then updates the mapping based on the current temperature and determined oscillator drift.