Frequency Hopping Timing Re-synchronization via Periodic Control Packets
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Solution Overview
Problem
In frequency hopping wireless networks, maintaining tight time synchronization at low duty cycles is challenging due to clock drift uncertainties, which requires frequent communication of timing information, consuming excessive energy and reducing device lifetime in battery-operated devices.
Innovation Solution
A battery-operated communication device 'quick-samples' a frequency hopping sequence at a low duty cycle and is synchronized by a main-powered device, which transmits control packets containing timing information to account for worst-case clock drift, allowing both devices to re-synchronize without burdening the battery-operated device with energy-intensive communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If nodes communicate timing information frequently to maintain tight time synchronization, then time synchronization accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic timing synchronization at predetermined intervals rather than continuous synchronization. The battery-operated device transmits timing information packets only at scheduled times, reducing communication frequency while maintaining acceptable synchronization accuracy. This periodic approach balances the need for time synchronization with energy conservation constraints.
Solution Approach 2:
The main-powered device predicts worst-case clock drift and pre-compensates for it in advance when transmitting timing information. By calculating and applying compensation values before drift becomes problematic, the system maintains synchronization accuracy without needing frequent correction communications, thus reducing energy consumption.
2Measurement precision
If battery-operated devices transmit timing information frequently, then time synchronization is maintained, but device lifetime is reduced
Solution Approach 1:
The system employs periodic timing synchronization where battery-operated devices communicate timing information only at predetermined intervals rather than continuously. This reduces the duty cycle of the transceiver, conserving battery energy and extending device operational lifetime while maintaining adequate time synchronization through the periodic exchanges.
Solution Approach 2:
The main-powered device assumes responsibility for predicting and compensating for clock drift, reducing the burden on battery-operated devices. The battery-operated devices simply transmit their observed timing information periodically, while the main-powered device performs the computationally intensive drift prediction and compensation calculations, extending battery life.
3Use of energy by moving object
If transceiver operates at low duty cycle to conserve energy, then energy consumption is reduced, but time synchronization error increases
Solution Approach 1:
The main-powered device predicts worst-case clock drift in advance and pre-compensates for it when transmitting timing information packets. By calculating compensation values before drift accumulates significantly, the system maintains synchronization accuracy even though timing communications occur only at low duty cycle intervals, thus resolving the trade-off between energy conservation and synchronization precision.
Solution Approach 2:
The system implements feedback mechanisms where timing information is exchanged periodically to detect and correct drift. The main-powered device uses received timing data to update its drift predictions and adjust future compensation values, ensuring synchronization accuracy is maintained despite low-duty-cycle operation.
Data Source
AI summary
In one embodiment, a battery-operated communication device “quick-samples” a frequency hopping sequence at a periodic rate corresponding to a substantially low duty cycle, and is discovered by (e.g., attached to) a main-powered communication device. During a scheduled sample, the main-powered communication device transmits a control packet to be received by the battery-operated communication device, the control packet containing timing information and transmitted to account for worst-case clock drift error between the two devices. The battery-operated communication device responds to the control packet with a link-layer acknowledgment containing timing information from the battery-operated communication device. Accordingly, the two devices may re-synchronize their timing based on the timing information in the control packet and acknowledgment, respectively.