Is your network PhaseReady?

attend the Phase Ready Seminar from Chronos

Phase Ready?

As you think about the evolution of your network, don't limit your thoughts to the frequency stability you need now. We want to help ensure that network roll-outs today will still be relevant come the explosion of HetNets and Small Cells.

An Independent Sceptic?

Very early in the development of PDH and SDH networks, carriers removed the timing functions from the network elements and implemented independent systems for time and timing dissemination and management. Interesting therefore that as timing requirements for edge applications are probably more stringent and difficult to achieve than ever, a large amount of timing dissemination and management is being taken back in to the network equipment!

What does that mean for you as a carrier? If you're a "bell head" traditional transmission person its a headache; if your a "net head" then perhaps not so much so. Fundamentally though to move microsecond phase coherence to the edge of your network you will need on-path support throughout (although don't jump to the conclusion that if you have on-path support that you will necessarily be successful in meeting all applications requirements).

But how well do these transparent and boundary clocks perform? What about the network in between them, especially if it is not in your control? Will the equipment vendor continue to support and improve their clock implementations for the long term? How do you manage failure scenarios? If you are using a managed service' phase implementation, how do you monitor its performance and hold them to account?

I think we at Chronos, and specialists like us, have a role to play in developing and maintaining your phase networks going forward. We can be that independent sceptic you need; one who understands the issues, can help with phase network design, verification, dimensioning and commissioning.

I will be developing these themes in the coming weeks and months. This is the biggest change in timing networks for at least twenty years and I believe we have the expertise and tools to help you make this process as pain free as possible!

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Beyond G.811

So what's beyond G.811? G.811 has been around since the 1980s - it was there when frequency distribution was eventually sorted for PDH, and still there in the 1990s when SDH came along and turned things upside down for a short while. Even in the late 2000s when PTP and packet sync threatened to fox us all, G.811 kept calm, carried on, and frequency distribution over PTP was eventually done & dusted.

So what about the 2010s? Well, the latest challenge sort of ignores G.811; it's the relentless drive for bandwidth, fuelled by smartphones, dongles & tablets that's causing the wireless operators to scratch their (egg)heads and dream up ways to cram more capacity in & around the macro network. Current thinking is to fill in the cracks with lots of small cells, adding capacity & taking some of the strain away from the macro layer. The term "HetNets" (Hetrogenous Networks) has been coined to describe wireless access over a variety of types of access node. Macro, micro, pico & femto cells - the term "Small Cells" covers the 3 smallest types. But if only were that easy. Adding more radio transmitters into the already crowded spectrum means there's more management to be done, to minimise radio interference between the (now more) numerous cell types. The clever technologies already described by Steve Newcombe go some way to limit this, but that's just the tip of the iceberg. The stringent phase synchronisation called for by these technologies is pushing sync delivery & the backhaul network to the limit in terms of what it can deliver. If efficient spectrum management calls for 100s of nS of phase sync right at the very edge of the network, this poses a interesting conundrum for networking equipment vendors to solve. Even with time & timing delivery using GPS, antenna delay calibration and system tolerances could take the error budget close to 100nS - sloppy installations are out, this is precision stuff!

Beefing up the network that supplies the sync is already underway. Initial discussions in the standards bodies have focussed on utilising already existing techniques in DSL & PON to get phase alignment carried across & out of the network nodes to the advantage of the small cell. Techniques like NTR in DSL and modem ranging in PON are already being silently used by the network to do its job, but these have never before been made available as phase-sync alignment tools to end applications… will they be standardised in time to help with small cells?

So G.811 might eventual have to step aside, and a new kid on the block might be revealed, the saviour of phase sync...

 

The "Is Your Network Phase Ready" seminar at Kings Place on May 8th has a session exploring what lies beyond G.811. We'll try to give an impartial view of the options currently available, and their possible impact on delivering microsecond phase. Places at the Seminar are FREE - sign up HERE today.

 

 

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