Head-End Time Lag Compensation for Broadcast Synchronization
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Solution Overview
Problem
Existing SFN networks face challenges in synchronizing transmitters due to variations in transport time and frequency caused by satellite position changes, leading to deviations in time references and frequency variations, making it difficult to maintain synchronized signals across the network without relying on GPS receivers at each site.
Innovation Solution
A method that determines a time lag between external and data stream-derived time references at the head-end, modifies time markers to compensate for transport time variations, and transmits this lag to transmitters, allowing synchronization without GPS receivers at each site, using techniques like pre-distorting time and frequency references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmitters use data stream-derived time references without GPS receivers, then device complexity is reduced, but time reference accuracy deteriorates due to transport time variations
Solution Approach 1:
The head-end system measures the actual transport time by comparing the external time reference with the data stream-derived time reference, then feeds back this measured time lag information to transmitters. Transmitters use this feedback to adjust their transmission timing, compensating for transport time variations and maintaining synchronization without requiring GPS receivers at each site.
Solution Approach 2:
The patent replaces the GPS-based mechanical/time reference system with a software-based time lag measurement and compensation mechanism. Instead of relying on GPS hardware at each transmitter site, the system uses time marker analysis and computational adjustment to achieve synchronization, substituting physical infrastructure with information processing.
2Area of stationary object
If transmitters are geographically dispersed, then network coverage area is improved, but time synchronization difficulty increases due to varying transport times
Solution Approach 1:
The system dynamically adjusts the time reference parameter for each transmitter based on its specific transport time characteristics. By measuring and communicating individual time lags to each transmitter, the system adapts timing parameters to accommodate geographic dispersion, allowing transmitters across different locations to synchronize their signals despite varying transport times from the head-end.
3Manufacturing precision
If time markers are modified to compensate for transport time, then signal transmission accuracy is improved, but data stream processing complexity increases
Solution Approach 1:
The head-end system performs preliminary measurement and calculation of time lags between external and data stream-derived time references before transmission. By pre-computing the necessary time compensation values and embedding them in time markers, the system prepares synchronization data in advance, reducing the processing burden on transmitters and simplifying their synchronization task while maintaining high transmission accuracy.
Data Source
AI summary
A method is provided for broadcasting a data stream in a network including at least two separate transmitters supplied by a head end. The stream is organized into data frames and includes at least one time marker. The method includes the following steps at the head end: obtaining a first time reference from an external source; obtaining a second time reference from the data stream received by the head end; comparing the first and second time references in order to determine a time shift between the first and second time references; and transmitting the time shift or at least one time marker modified on the basis of the time shift in order to compensate for a transport time variation between the head end and the transmitters.