Isochronous Node Time-Locked Loop for DTV Synchronization
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Solution Overview
Problem
Current time synchronization methods in digital television distribution networks, such as GPS receivers and Network Time Protocol (NTP), are inadequate due to potential interference, equipment failures, and limited accuracy, necessitating a more efficient alternative for maintaining clock synchronization across network nodes.
Innovation Solution
A node with a time-locked loop and isochronous transport links for bidirectional exchange of time information, allowing nodes to synchronize clocks using remote and local time information, eliminating the need for GPS receivers and enhancing network resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS receivers are used for time synchronization in SFN transmitters, then clock synchronization accuracy is improved, but system reliability deteriorates due to vulnerability to jamming and equipment failure
Solution Approach 1:
The patent introduces an intermediary time distribution mechanism where a master node distributes time information to slave nodes through a controlled network. This intermediary approach replaces direct GPS dependency with a network-based time transfer system that uses timestamp exchange and delay compensation to achieve synchronization without relying on external GPS signals that can be jammed or fail.
Solution Approach 2:
The patent implements feedback mechanisms where slave nodes send timestamp information back to master nodes, allowing for delay compensation and continuous adjustment. This feedback loop enables the system to adapt to changing network conditions and maintain synchronization accuracy while eliminating dependency on vulnerable GPS receivers at each transmitter site.
2Device complexity
If NTP is used for time synchronization in non-dedicated networks, then device complexity is reduced, but measurement precision deteriorates due to limited accuracy
Solution Approach 1:
The patent segments the time synchronization function by separating master nodes that maintain reference time from slave nodes that perform local synchronization. This segmentation allows the system to achieve high precision through coordinated time transfer between segmented components, while keeping individual node complexity manageable through standardized interfaces and protocols.
Solution Approach 2:
The patent replaces the mechanical/GPS-based time synchronization system with an information-theoretic approach using timestamp exchange and mathematical delay compensation. This substitution achieves higher precision by using software-based time transfer algorithms rather than hardware-based GPS receivers, thereby improving accuracy while maintaining acceptable system complexity.
3Measurement precision
If GPS receivers are installed at all transmitter sites, then time synchronization accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the time distribution network serve multiple functions: it distributes both time synchronization information and regular data traffic through the same network infrastructure. This multi-functionality eliminates the need for separate GPS receivers at each transmitter site, reducing device complexity and cost while maintaining synchronization accuracy through the universal time transfer mechanism.
Solution Approach 2:
The patent uses copying of time information through timestamp exchange between nodes rather than physical copying of GPS signals. Time information is replicated and distributed through network messages, allowing multiple nodes to access synchronized time without requiring physical GPS receivers at each location, thereby reducing infrastructure complexity.
Data Source
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AI summary
There is provided a node for facilitating time distribution in communication networks, and more specifically for time synchronization in digital television (DTV) distribution network. The node comprises an interface, a clock for establishing a local time, and a time-locked loop. The interface is configured for interconnecting the node to at least one neighboring node over an isochronous transport link for transmission and reception of repetitive frames comprising time information. The time-locked loop is configured for, based on remote time information received via the interface and local time information from the clock, synchronizing the clock to the clock of one of the at least one neighboring node. This facilitates that the node, or a corresponding synchronous network comprising nodes according to the inventive concept, is rather insensitive to network delays. In this way the requirements on the network infrastructure are reduced. In particular, there is no need for dedicated networks. Further, a synchronous network, a method for the node and a method for a synchronous network is provided.