Network Node Synchronization for IPTV End-Terminals
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Solution Overview
Problem
Existing synchronization schemes for IPTV systems face scalability limitations and increased costs due to the need for central synchronization masters, distributed control schemes, and controllable variable-delay buffers, which also result in significant adaptation time for new users to synchronize with existing end-terminals.
Innovation Solution
A method and system that synchronize end-terminals by calculating delay information at network nodes using arrival time information from central or local clocks, allowing variable delay units to adjust packet transmission, eliminating the need for adaptive-delay buffers in end-terminals and enabling simultaneous synchronization of large groups of viewers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If controllable variable-delay buffers are implemented in end-terminals to achieve synchronization, then group-synchronization can be achieved, but the cost of end-terminals increases and legacy terminals cannot be used
Solution Approach 1:
The patent introduces network nodes as intermediaries between the streaming server and end-terminals. These network nodes implement the variable-delay buffer functionality and synchronization control, acting as mediators that enable group-synchronization without requiring modifications to end-terminals. The network nodes receive streams, apply delay adjustments based on timing information, and forward synchronized streams to multiple end-terminals.
Solution Approach 2:
The patent enables legacy end-terminals to participate in synchronized groups without any modifications or additional capabilities. The synchronization functionality is self-contained in the network nodes, which automatically adjust delays and coordinate timing without requiring end-terminals to have variable-delay buffers or process timing information. This allows end-terminals to simply receive and play back streams as they traditionally would.
2Reliability
If controllable variable-delay buffers with additional functionality are added to end-terminals, then synchronization can be achieved, but the cost of end-terminals increases
Solution Approach 1:
The patent shifts the synchronization functionality from end-terminals to network nodes, which act as intermediaries. The network nodes implement variable-delay buffers and timing control mechanisms, eliminating the need for expensive specialized components in end-terminals. This allows standard, lower-cost end-terminals to be used while maintaining synchronization capability through the network infrastructure.
3Reliability
If local buffering at end-terminals is used for synchronization, then group-synchronization can be achieved, but significant adaptation time is required when a user joins a synchronized group
Solution Approach 1:
The patent implements preliminary timing adjustments at network nodes before streams are delivered to end-terminals. Network nodes calculate required delays in advance based on timing information from synchronization protocols (NTP, PTP, or GPS), and pre-adjust streams using variable-delay buffers. This preliminary synchronization eliminates the need for end-terminals to perform local buffering and adaptation, allowing users to join synchronized groups immediately without waiting for buffering periods.
4Reliability
If a central synchronization master is used to collect timing information from all end-terminals, then group-synchronization can be achieved, but scalability is limited to a limited number of end-terminals
Solution Approach 1:
The patent segments the synchronization function by implementing it at network nodes rather than having a single central master collect information from all end-terminals. Each network node independently performs synchronization for its connected end-terminals, dividing the large-scale synchronization problem into smaller, manageable segments. This segmentation allows the system to scale to many more end-terminals than a single central master could handle.
Solution Approach 2:
The patent introduces network nodes as intermediaries between the central timing source and end-terminals. These intermediaries receive timing information and distribute it locally, reducing the communication overhead on the central synchronization master. This intermediary layer enables the system to scale to larger numbers of end-terminals by distributing the synchronization workload across multiple network nodes rather than concentrating it at a single point.
5Reliability
If a distributed control scheme is used where each end-terminal multicasts timing information, then group-synchronization can be achieved, but a multitude of multicast channels are required which is a limited resource
Solution Approach 1:
The patent uses network nodes as intermediaries that centralize the collection and distribution of timing information. Instead of each end-terminal multicasting to all others (requiring N*(N-1) multicast channels), network nodes collect timing data and distribute synchronization information centrally, reducing multicast channel requirements to a manageable number corresponding to the network topology rather than the square of the number of end-terminals.
Data Source
AI summary
A method is described for synchronizing the transmission of a stream to a group of end-terminals. The method is used in a system comprising a station transmitting a packetized stream over a network to at least a first and second network node. Each network node comprises a variable delay unit and each network node is connected to one or more end-terminals. In the method the synchronization unit receives arrival time information of a packet in the broadcast stream at the first and second network node. Delay information is calculated for the first and second network node on the basis of the arrival time information of the packet. Further, the delay information is transmitted to the first and second network node so that the variable delay unit in the first and second network node is able to transmit the broadcast stream to the first and second end-terminal in a substantially synchronized way.