Frequency-Hopping Sensor Synchronization via Public Time Signals
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Solution Overview
Problem
Security system sensors face challenges in maintaining synchronization with control panels during sleep mode due to the need for a lengthy negotiation phase, which impacts battery life and is restricted by FCC regulations on beacon transmissions.
Innovation Solution
The method utilizes an external publicly accessible broadcast time signal, such as GPS or cellular signals, to calculate a frequency hopping index pointer, allowing sensors to synchronize with control panels without the need for lengthy negotiation, by accessing a shared frequency hopping table and selecting channels for data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors use internal timebase to maintain synchronization during sleep mode, then synchronization accuracy is improved, but power consumption increases and battery life decreases
Solution Approach 1:
The system performs synchronization negotiation during the brief wake periods when sensors are already active to send data, rather than maintaining continuous timebase operation. The control panel transmits beacon signals at predetermined intervals, and sensors synchronize during their necessary wake periods, eliminating the need for continuous power-consuming timebase maintenance while ensuring synchronization accuracy is achieved when needed
2Measurement precision
If control panel transmits beacon signals for synchronization, then synchronization capability is improved, but transmission time increases and FCC compliance becomes difficult
Solution Approach 1:
The system uses publicly available broadcast time signals (such as GPS or cellular network timing signals) that serve multiple purposes: they provide accurate time reference for synchronization, they are already transmitted by infrastructure providers, and they comply with FCC regulations since they are not custom beacon transmissions. This eliminates the need for dedicated synchronization beacons while maintaining synchronization capability
Solution Approach 2:
The invention introduces an intermediary public time signal source that both the control panel and sensors can independently access. Instead of direct peer-to-peer beacon transmission requiring lengthy negotiation sequences, both devices use the same external time reference to independently determine synchronization, dramatically reducing the time required while ensuring both parties are synchronized to the same reference
3Measurement precision
If sensors wake up frequently to synchronize with control panel, then synchronization accuracy is improved, but battery life decreases
Solution Approach 1:
Sensors independently acquire the public time signal and autonomously calculate their frequency hopping position without requiring active synchronization negotiation with the control panel. This self-service approach allows sensors to remain in low-power sleep mode longer, waking only briefly to acquire the time signal and transmit data, thereby extending battery life while maintaining synchronization accuracy
Data Source
AI summary
A method for synchronizing a security system control panel and a sensor. The control panel and the sensor each have a transceiver. The control panel monitors a publicly broadcast signal for an time signal, periodically receives the time signal, calculates a frequency hopping index pointer using the time signal and accesses a frequency hopping table using the frequency hopping index pointer. The frequency hopping table is used by the control panel to determine when to hop between multiple receiving channels and which of the receiving channels to hop. The sensor wakes up from a standby mode when the sensor determines that the sensor is to send data, receives the publicly broadcast signal that includes a time signal, selects the channel that the control panel is actively receiving data using the time signal and transmits the data to the control panel using the selected channel.