Selectable Loss of Signal Criteria for Serial Receivers
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Solution Overview
Problem
Existing SONET/SDH communication systems face issues with false LOS alarms and delayed PLL lock due to differences in data rates, leading to erroneous data transmission and loss of signal during errors, which existing technologies fail to adequately address.
Innovation Solution
A method for selecting customizable LOS criteria in a serial communications receiver, allowing for combination testing of signal detect, run length, signal strength, harmonic band detection, and received data clock tests to generate a LOS signal only when multiple criteria are met, thereby preventing false alarms and enabling faster PLL reacquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single signal strength test is used to detect LOS, then the detection simplicity is improved, but false alarms increase due to signal variations during rate transitions
Solution Approach 1:
The patent combines multiple LOS detection criteria (signal strength threshold, run length criteria, and harmonic band detection) into a unified detection mechanism. The LOS signal is generated only when a predetermined number of these combined criteria are met, reducing false alarms while maintaining detection simplicity through automated multi-parameter evaluation.
2Measurement precision
If LOS criteria are strictly enforced without customization, then the detection accuracy is improved, but adaptability to different data rates and signal conditions deteriorates
Solution Approach 1:
The patent implements dynamic LOS criteria that automatically adapt to different data rates and signal conditions. The system adjusts detection parameters based on the received signal characteristics, allowing the same LOS detection mechanism to accurately operate across multiple data rates (e.g., DS-3, OC-3, OC-12) without requiring manual reconfiguration.
Solution Approach 2:
The system changes detection parameters dynamically based on signal conditions. Different LOS criteria (signal strength thresholds, run length values, harmonic band frequencies) are selected and applied based on the detected data rate and signal characteristics, enabling accurate detection across varying operational conditions.
3Reliability
If multiple LOS criteria are evaluated simultaneously, then the false alarm reduction is improved, but the detection complexity increases
Solution Approach 1:
The patent segments the LOS detection process into distinct functional blocks: signal strength evaluation, run length analysis, harmonic band detection, and criteria combination logic. Each segment handles a specific aspect of LOS detection, making the overall complex system manageable through modular design while achieving reduced false alarms through combined criterion evaluation.
4Reliability
If the PLL bandwidth is reduced to filter wander components, then the filtering performance is improved, but the lock acquisition time increases
Solution Approach 1:
The patent implements preliminary LOS detection using multiple criteria before the PLL completes lock acquisition. By detecting LOS conditions early through signal strength, run length, and harmonic band analysis during the acquisition phase, the system can identify and respond to LOS conditions without waiting for the PLL to fully lock, thereby reducing the effective loss of time despite the PLL's inherent acquisition delay.
Data Source
AI summary
A system and method are provided for selecting loss of signal (LOS) criteria in a serial communications receiver. The method receives a serial stream of digital data and selects LOS criteria. The serial stream of digital data is compared to the selected LOS criteria. In response to the serial stream of digital data failing to meet the selected LOS criteria, a LOS signal is generated. Some examples of the LOS criteria that might be selected include: a “signal detect” signal received from the source transmitting the serial stream of digital data, a run length test, a signal strength (voltage amplitude) test, harmonic band detection test, and a received data clock test. In one aspect, selecting LOS criteria includes selecting combinations of the above-mentioned LOS criteria, so that the LOS signal is generated in response to failing to meet the combination of selected LOS criteria.