Dynamic Phase-Locked Loop Gain Renormalization With Phase Compensation
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Solution Overview
Problem
Satellite delivery of DVB-T transport streams in Single Frequency Networks (SFNs) faces challenges due to packet jitter, RF noise, and weather-related interference, leading to potential destructive interference and transmitter outages, which existing error correction methods cannot fully mitigate.
Innovation Solution
The SciMux system combines multiple DVB-T transport streams into a single carrier using Digital Transport Formatters (DTFs) and Multiple Transport Receivers (MTRs), employing Adaptation Fields to coordinate timestamps and correct packet jitter, and incorporates In-Band Controllers for secure, flexible, and resilient data routing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If satellite delivery is used to convey transport streams to distributed modulators, then installation cost is reduced and deployment time is shortened, but packet jitter and transmission errors increase due to RF noise and weather interference
Solution Approach 1:
The system pre-calculates and applies compensation values for satellite positional drift and packet jitter before transmission. Timestamps are adjusted in advance to account for expected variations in satellite position and transmission delays, allowing the receiving modulators to synchronize without being affected by the jitter that would otherwise occur during normal operation.
Solution Approach 2:
The invention dynamically adjusts transmission parameters including packet timing and timestamps based on satellite position data. By changing the timing parameters of packet transmission and insertion based on predicted satellite drift, the system maintains synchronization accuracy despite the unreliable satellite transmission medium.
2Device complexity
If multiple transport streams are combined into a single satellite carrier, then system complexity is reduced and security is improved, but packet jitter increases making synchronization difficult
Solution Approach 1:
The system introduces an intermediary processing layer that combines multiple transport streams into a single satellite carrier while maintaining synchronization information. The combining methodology uses intermediary timestamp adjustments and compensation mechanisms to ensure that even though streams are merged, the original synchronization precision is preserved through careful management of packet timing and identifier assignment.
Solution Approach 2:
Before combining multiple transport streams into the single satellite carrier, the system pre-processes each stream by assigning adjusted timestamps that account for expected jitter. This preliminary timing adjustment ensures that when streams are combined and transmitted, they can be accurately re-synchronized at the receiving end despite the combined stream's inherent jitter.
3Reliability
If modulators wait for GPS-synchronized mega frames to ensure temporal alignment, then signal synchronization is improved, but transmission delays increase during resynchronization events
Solution Approach 1:
The system implements feedback mechanisms where modulators continuously monitor packet arrival timing and use this information to adjust their transmission timing. By providing feedback on actual packet reception times and using compensation values based on satellite position, the system maintains synchronization without requiring periodic resynchronization pauses, thus eliminating transmission delays while preserving signal synchronization.
Data Source
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AI summary
A variable bandwidth phase locked loop (PLL) includes renormalizable circuitry configured to allow a gain of the PLL to be changed without causing a disturbance, and a phase compensation circuit configured to adjust a final output phase of the PLL based on parameter changes supplied to the PLL.