Wireless Fire Gateway Frequency Hopping Coexistence
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Solution Overview
Problem
Wireless fire detection systems face interference issues in large setups, limiting the number of detectors that can be used effectively due to mutual interference among radio frequency signals from adjacent gateways.
Innovation Solution
The system employs frequency hopping techniques, including the use of unique seed values to offset the starting point of each gateway's frequency list, and alternating between two sets of frequencies to minimize interference, ensuring reliable communication between sensors and gateways without simultaneous frequency usage by adjacent gateways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wireless fire detectors are distributed around a secured area to improve fire detection coverage, then the reliability of fire detection is improved, but mutual interference among radio frequency signals from adjacent gateways increases, limiting the number of detectors that can be used effectively
Solution Approach 1:
The system dynamically changes frequency channels over time using frequency hopping spread spectrum technology. Each gateway and detector periodically switches between multiple frequency channels according to a pseudorandom sequence, ensuring that adjacent gateways do not continuously interfere with each other. This dynamic frequency allocation resolves the contradiction by making the radio frequency environment time-variant, reducing mutual interference while maintaining comprehensive fire detection coverage
Solution Approach 2:
The system implements periodic frequency channel switching at predetermined intervals. Gateways and detectors alternate between different frequency sets (e.g., Set A and Set B) in a periodic manner, with each gateway using unique seed values to offset their frequency lists. This periodic action ensures that interference occurs only during brief transition periods rather than continuously, allowing reliable fire detection across multiple distributed gateways
2Area of stationary object
If the number of fire detectors is increased to improve detection coverage, then the area under monitoring is expanded, but interference among radio frequency signals increases, limiting system scalability
Solution Approach 1:
The system segments the frequency spectrum into multiple channels and organizes gateways into different groups that operate on different frequency sets. Each gateway is assigned a unique seed value that offsets its frequency list, creating segmented frequency allocation across the network. This segmentation allows multiple gateways to coexist in the same physical space without excessive interference, enabling expansion of the monitored area while maintaining signal quality
Solution Approach 2:
The system adds the time dimension to frequency allocation by implementing frequency hopping over time. Instead of static frequency assignment, the system uses time-varying frequency sequences where each gateway hops through multiple frequency channels according to its unique seed value. This dimensional transformation from static to dynamic frequency allocation enables scalable expansion of the monitored area by allowing more gateways to share the spectrum through time-division multiplexing in the frequency domain
Data Source
AI summary
A method and apparatus are provided, the method incorporating the steps of detecting other interfering wireless gateways of the security system, their frequency hopping pattern, their phase relative to a time reference and a dwell time relative to the time reference, selecting a channel set and a phase of operation for communicating with a plurality of sensors relative to the time reference using frequency hopping based upon the detected frequency hopping pattern, the phase and dwell time of the other wireless gateways, communicating with the plurality of sensors and periodically comparing its phase of operation with the phase of the other interfering wireless gateways and adjusting its phase based upon the comparison with the phase of the other interfering wireless gateways.