IP Network Timing Synchronization via UDP Stream Extraction
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Solution Overview
Problem
Traditional port networks and media gateways in IP networks face challenges in synchronization without external timing sources, as they cannot interface directly with Center Stage Switches, and relying on NTP or GPS requires hardware and software development, making it costly and complex.
Innovation Solution
The solution involves deriving timing from the PSTN and distributing it through the network using UDP streams, allowing gateways to synchronize internally without external timing sources or hardware, using digital signal processors to manage and distribute timing across the network, creating synchronization domains with master, tandem, and slave members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NTP or GPS is used for synchronization, then timing accuracy is improved, but hardware and software development complexity increases
Solution Approach 1:
The system uses its own internal resources (existing IP network infrastructure and local clocks) to provide synchronization services, eliminating the need for external NTP servers or GPS receivers. Each gateway derives timing from PSTN signals received through existing telephony interfaces, and distributes this timing autonomously within the network.
Solution Approach 2:
The existing IP network infrastructure and gateway devices are made to serve dual purposes: their primary function for voice telephony and their secondary function for distributing synchronization timing. The same network connections used for carrying voice traffic are also used to distribute timing information, eliminating the need for separate synchronization hardware.
2Reliability
If reference boards are installed in all port networks or media gateways, then system-wide synchronization is achieved, but cost increases
Solution Approach 1:
The patent introduces an intermediary mechanism where timing information is embedded within existing IP network traffic streams. Instead of requiring direct physical connections to reference clocks at each device, the timing data is transported through the IP network using standard protocols, allowing any gateway to receive and distribute synchronization information without special hardware.
Solution Approach 2:
The system creates copies of timing information from a single reference source and distributes these copies throughout the network via IP streams. Multiple gateways can receive identical timing data from the PSTN signal and use it locally, eliminating the need for physical reference board installations at each location.
3Measurement precision
If dedicated hardware timing sources are used, then timing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical/physical timing distribution systems (dedicated hardware timing sources, fiber connections to CSS) with an electronic/software-based solution using IP network protocols. Timing information is transmitted as data packets over the existing IP infrastructure, substituting physical timing distribution with digital signal processing and network protocol mechanisms.
Data Source
AI summary
Network timing is derived from the PSTN and distributed through the network to gateways capable of deriving timing from the incoming UDP stream. The derived timing has the correct frequency for voice telephony without using external timing sources or extraneous hardware components. For example, a digital signal processor (DSP) can derive the timing from a timed TDM bus and distribute messages, such as IP messages, to other gateways or port networks. The other gateways and port networks use the incoming stream to extract the timing which is then used to time their TDM bus. The port networks and gateways can also distribute other streams to other gateways in a fan-out type of arrangement. This internally generated timing can be used, for example, for Circuit Emulated Services (CES).