Per-Call Noise Threshold Adjustment for Alarm Signal Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing security systems face challenges in distinguishing between noise and data signals on telecommunications lines, particularly due to random noise fluctuations, which are exacerbated by VoIP services, making it difficult to set a single rule for signal detection across all calls.
Innovation Solution
A method and apparatus that measure noise levels in specific frequency bands before signal transmission, adjusting signal detection thresholds on a per-call basis to ensure that only signals exceeding the noise level are detected as data signals, using a noise detector, signal detector, and controller to differentiate between noise and data signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single signal detection threshold is used for all calls, then the device complexity is reduced, but the reliability of signal detection deteriorates due to random noise fluctuations
Solution Approach 1:
The signal detection threshold is made dynamic by adjusting it on a per-call basis according to the measured noise level for that specific call, rather than using a fixed threshold for all calls. This allows the threshold to adapt to varying noise conditions while maintaining detection reliability.
Solution Approach 2:
The detection threshold parameter is changed adaptively based on the measured noise characteristics of each call. By measuring the noise level in the frequency band and setting the threshold accordingly, the system optimizes detection accuracy for each unique call condition.
2Reliability
If signal detection threshold is set above noise level for each call, then the reliability of signal detection is improved, but the device complexity increases due to per-call noise measurement and threshold adjustment
Solution Approach 1:
The noise level is measured in advance during the call setup phase, before actual alarm data transmission begins. This preliminary measurement allows the threshold to be pre-configured for optimal detection during the data transmission phase, without adding complexity to the main detection process.
3Measurement precision
If noise measurement is performed in the absence of signals, then the measurement precision of noise level is improved, but the loss of time occurs due to additional measurement period before signal transmission
Solution Approach 1:
The noise measurement is performed as a preliminary action during the call establishment phase, utilizing the natural silence period before alarm data transmission begins. This approach captures accurate noise characteristics without significantly extending the overall call setup time, as the measurement occurs during the inherent delay before data exchange.
Data Source
Figure 1
Figure 2~3
Figure 4A
AI summary
A method at an alarm monitoring station and security system arrangement for detecting alarm signals originating at security systems on incoming calls carried by a telecommunications line includes, for each call, measuring a noise level on the line in the absence of signals originated by the security systems. Based on the measuring, at least one signal detection threshold above the noise level is set, wherein a level of a signal must exceed the signal detection threshold in order to be detected as a data signal. Alarm data signals in the call are detected using the signal detection threshold.