In legacy digital telecom networks, frequency synchronisation was essential to ensure the optimal performance of your network, and the ability of your network to connect successfully with others. But the world is changing, says Steve Newcombe, Chronos Technology.
The move from such technologies as Plesiochronous Digital Hierarchy (PDH) and Synchronous Digital Hierarchy (SDH) to Canier Ethernet means the transport mechanism itself no longer requires timing, but applications at the edge of these networks maywell do.
In response to this paradigm shift, Precision Time Protocol (PTP) was adapted by the carrier community from a technology used in local area networks in industrial applications. However, this took away the deterministic transport of timing via the transport network to the dissemination of time and timing becoming just another network service.
Delivering adequate frequency synchronisation for mobile networks using PTP and SyncE has been successfully implemented across the wood; Long Term Evolution (LTE) Advanced services and 5G Time Division Duplex (TDD) timing constraints bring a whole new challenge to delivering edge network time and phase synchronisation.
But why not use Global Navigation Satellite System (GNSS) timing across the edge of the network? We know we can derive very accurate time synchronisation from GNSS signals. Indeed, but what happens if the antenna fails? In order to deliver a costeffective network edge, devices simply cannot hold adequate timing performance for the time it takes to mobilise to fix the failure. So, we must think of a scalable, reliable method of delivering that microsecond timing performance to the edge of the network, and Microchip's Virtual Primary Reference Time Clock (vPRTC) is by far the best way to deliver this, using the High-Performance Boundary Clock (HPBC) capability of the TimeProvider 4100 platform.
Simply put, Chronos can deliver time and phase alignment to within a hundred nanoseconds of Coordinated Universal Time (UTC) and phase alignment to any points of presence across your network; you really can tum the Isle of Dogs into a Primary Reference Time Clock (PRTC)! Using a dedicated wavelength of fibre between TimeProviders we can deliver timing performance approaching picoseconds without the need for an expensive and maybe even unobtainable GNSS installation.
By including some core ePRTC sites using Microchip's Caesium Atomic Clock technology allied to GNSS to hold timing performance to 100 nanoseconds for 14 days or more, vPRTC can bring an independent, deterministic, timing platform to your whole network. And at each of these HighPerformance Boundary Clock sites, you can support up to 16 southbound network connections using a variety of timing protocols to deliver the microsecond performance on a sustainable basis across the edge of the network. vPRTC networks can be designed with East West resilience, ensuring whatever happens in the core of the network will have little or no impact on edge performance.
Using BX SFPs distances of up to 95km between HPBCs have been successfully implemented in live networks, with distances of over 150km covered using special Raman filters and CWDM SFPs. The type of SFP is a significant factor in delivering this performance; the TimeProvider 4100 is agnostic to the SFP and wavelength deployed.