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.

Steve joined Chronos as an Account Manager in April 2006, although his connection with Symmetricom and its constituents goes back to 1999. Steve's involvement in telecommunications began in 1984 as an antenna design engineer, progressing into engineering management and culminating in Director status of a leading UK antenna manufacturing and installation business. He moved into the Sales environment in 1999 selling Symmetricom (formerly Datum) time and timing synchronisation solutions for enterprises and telecomms carriers. Steve holds a Master of Science Degree and is a Member of the IET.

Kings Place - another successful day

Thanks to everyone who attended our Kings Place (@Kingsplaceevent) event yesterday. I think it was a great success and as well as provoking thought about how best to deliver phase to the edge of the network in an operationally supportable way, we also had time to debate the future of engineering!

Use of TDD spectrum also had a good airing; interesting developments in Japan at 3.5GHz could mean phase is essential not only to ensure you use your own spectrum efficiently, but that you don't compromise your competition!

Special thanks to our independent Keynote speakers Zahid Ghadialy (@zahidtg) from TechUK and Hans Sjöstrand from Transmode.


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Free PhaseReady Event - London, Wednesday June 3rd

Registration is now open for the latest PhaseReady event at Kings Place London on Wednesday June 3rd. This is the latest in our series of events at this excellent venue, addressing the challenges and solutions available for timing in next generation networks as these networks, services and applications have evolved.

Entitled "Supporting Your Phase Network", we will be discussing the keys areas of preparing for, planning, testing, rolling out and monitoring your timing network to reliably deliver microsecond phase to the edge of your network.

We will be joined for keynote addresses from industry expert Zahid Ghadialy, Transmode's Hans Sjöstrand and Microsemi's Simon Butcher.

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Kings Place Agenda finalised

We've secured our Keynote speakers for this year's Kings Place event and the Agenda should give us a really productive and intersting day. You can register for free HERE.

Supporting Your Network Phase

View the agenda here»

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Do you understand how Phase will be delivered to the edge of your Network?

If you're planning, or working towards planning, to rollout out LTE-TDD or LTE-A services, do you know what technologies are available to you and how your network can support these? How do ITU Standards fit in with your network? If you will have Operational responsibility for a Phase Delivery system, how do you ensure you can support it in a timely fashion with the resources you will have available? What Element and Network Testing do you need to do to prepare for this, and how will you interpret any results?

How much of your network is in your direct control? Will you have the ability to be responsible for your own Timing Delivery? Will your voice be loud enough in your own organisation to make this a success? How much resource will you have for planning and preparation? How many PoPs do you have that can support deployments of equipment to support your Edge Timing? How well will your Edge Microwave support Phase Delivery? How will you keep an eye on Timing Delivery performance? How will your Timing Delivery cope with rerouting and Switch, Router and Gateway failure? How will your Timing Delivery cope with Timing Equipment failure?

That's a lot of questions and although we won't have the answers to all of them we do have a clear vision of the range of challenges you face, and the toolkit we have available to enable you to deliver microsecond phase to the Network Edge in a manageable and supportable way.

Come to our free event at Kings Place ( on Wednesday June 3rd; I can't guarantee you will leave with fewer questions than when you arrive, but you will have the answers to most of them at your disposal! Register now for free at

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Donut or Doughnut - the wrong question?

Back in March I blogged asking whether you (well your phase delivery network actually) were a donut or doughnut person. The donut would be a ring of PRTCs (Primary Reference Time Clocks) at the edge of your network access layer delivering phase to Gateway devices and eNodeBs.The doughnut would have resilient (perhaps Caesium supported) PRTCs in your network core. The terms of this question were really about a battle of technologies as well as network architecture. I've since realised that this question is really not valid for a reliable supportable phase delivery network for TDD and LTE-A services that you are now on the verge of rolling out.

For me most of the technology issues are resolved (microwave links delivering phase being the most challenging), although implementations will vary wildly and standards have yet to catch up with real world network issues.

I think the key requirement for a phase delivery network is not the timing technology that underlines it but what happens when things fail! For example GPS directly connected at the eNodeB or Cell Site Gateway should easily deliver 1.5us at the air interface, but for how long will it continue to meet this requirement if some kind soul cuts through the GPS cable? Will it be long enough for your field force to get to site and effect a repair before the timing requirement is breached at an economic cost?

With this in mind I believe that the ideal phase implementation may well be a donut supported by a doughnut! I also believe this will be best delivered by an phase system independent of the network equipment. With PRTCs at the donut layer supported by PRTCs in the doughnut; especially if supported by Caesium in the core and Automatic Path Asymmetry Compensation (as implemented in the TimeProvider 2700) at the donut layer; next day mobilisation of field force could still allow fixes before the network edge breaks the 1.5us barrier.

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GPS Timing - coming to the edge of a Network near you?

This may seem a strange title for many readers - if you have a CDMA network you've been working with GPS at cell sites for many years. Here in Europe however we have tended in the past to use the E1 used for backhaul to deliver the sync quality we need to deliver 15ppb at the air interface. We've also more recently delivered this frequency performance from the core of Carrier Ethernet networks using PTP and SyncE.
Should your GPS have a problem, the holdover oscillator (lets say an OCXO) kicks in and gives you time to get out to site and make a fix. Likewise the PTP client devices usually use OCXO for holdover, and although the time to fix is usually shorter than is the case for GPS there is still adequate time to mobilise for a fix.

So why consider GPS at the edge now? Well we're probably a year or so away from having to roll out TD-LTE, or LTE-A features, that require adjacent cells (Macro or Small Cells) to be within +/-1.5us of each other. Packet based timing from the core is still being tested and standardised; microwave radio manufacturers have a real challenge to make this work well (and they're doing great work to get there);and you may not have end to end control of the backhaul network in any case. These issues may or may not be performance affecting enough to put a brake on considering PTP supported by SyncE for phase, but you'd be a fool not to consider the alternatives.

So we examine GPS at the edge; its been done successfully for years, right? Trouble is the game has changed - its got a lot harder. We're all OK with your GPS timing solution locked and running as it should, but what about failure? As in frequency networks the holdover technology kicks in - but OCXO will only hold the +/-1.5us for probably four HOURS, not four DAYS! Have you got the budget, or indeed available power in the cabinet, to use OCXO? TCXO performance continues to improve in leaps and bounds so perhaps using the latest TCXO could give you three hours to mobilise. How is Ops going to handle this? Will you need vehicles parked at strategic motorway junctions waiting for equipment to fail?
On a practical level where can you put the antenna? Have you mast space and the personnel required to roll this out at thousands of locations? Can you hide the antenna in the cabinet? Will it see enough of the sky to work there? Could you roll out Assisted GPS (A-GPS) to help here? If you deploy antennas at low level how long before they're vandalised? Does your network design allow for other cells to provide backup sync? If your timing is embedded in the eNodeB do you have to swap out a whole box to solve a GPS or sync issue?

These issues are real and need addressing, but none of them are necessarily show stoppers to delivering a robust network with adequate phase performance. The trick is to know what the issues are and to address them head on. Don't hope things won't go wrong because they will. Examine the cases of Edge GPS and Phase from the Core from a position that with the right planning and testing they will work.

Make sure you and your network are Phase Ready!
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Edge Microwave - Transparent or Boundary Clock?

We've been fortunate enough at Chronos to work with several microwave equipment manufacturers in the last year or so, helping them develop and test their implementations of On Path Support for Edge Phase applications. We have seen some quite astonishing improvements in Packet Delay Variation (PDV) of PTP packets when implementing a Transparent Clock; actually in turning the radio link in to a virtual Transparent Clock.

All the manufacturers we have spoken to (of course this is not ALL manufacturers!) are implementing a version of this Transparent Clock. They have come to this conclusion independently, I think because they realise that the many variations that the radio link can encounter due to loading, bandwidth use, scheduling, weather or other external factors means that simply terminating the PTP flow at the link "Ingress" and generating a fresh flow at the "Egress" will not deliver the standard of output clock needed to support a living and breathing network.

I was surprised therefore when I discovered that manufacturers were under external pressure to deliver Boundary Clock rather than Transparent Clock. The main two reasons seem to be that use of Boundary Clock for Phase is now standardised whereas Transparent Clock is not, and that Transparent Clock breaks OSI Layer boundaries.

We are actually beginning some tests in the next week or so to start to characterise some microwave links' PDV and their effect on Boundary Clock performance. In my opinion the fact the the standards bodies can't keep up with technology should not be a brake on development, and is no surprise to any of us in any case! The Layer Violation argument seems a bolt on excuse to me - if the manufacturers believe Transparent Clock is the best way to deliver On Path Support then we should get on with supporting them in the standards!

A poorly working compromise will simply not do in the urban Small Cells space. We're in a different world now and what works should be what is implemented.

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Small Cells World Summit - sync is creeping on to the agenda!

Had the pleasure of contributing to a panel discussion at the Small Cells Backhaul Summit at the ExCeL last week. We had half an hour on the topic "Time and timing distribution for small cells". My co-panellists were Martin Kingston, Principal Designer at EE and Richard Strike, Business Development Manager, Ethernet Access at ADVA Optical Networking; and it was ably moderated by Rami Yaron. The discussion really centred on getting phase to the edge of mobile networks, and how the business case stacks up to achieve this.

Now half an hour doesn't seem like much, and in fact the discussion could have gone on for a LOT longer, but it is half an hour more than last year's event! There were a lot of presentations in the Backhaul Summit that mentioned to various degrees how difficult getting phase to the network edge is going to be, but no real expansion on that at all.

I was pleased that my view of the world chimed pretty well with Martin's; I've known him for many years now and respect his judgement and so if we are in accord I know I'm doing something right! Interestingly the area where we parted company was an unexpected one for me. I've thought that Small Cells would be more expendable than Macro Cells, and that operators could probably stand availability levels less than the five-nines we're used to in the Core. Martin was quite clear that if it is on his network it needs to be available! This will have quite an impact on timing and backhaul technologies; and pose some interesting questions for Small Cell holdover capability.

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Donut or Doughnut? Where will your Phase come from?

I've spent a lot of time since the beginning of the year talking to carriers and equipment vendors about the problems using PTP to get phase sync to the edge of networks. This includes talking to both the carrier and vendor about a network that is being installed this year and will need edge phase sync down the line. I've also spoken to two mobile carriers with very different philosophies of likely network rollout to achieve adequate phase sync, and another operator planning a network for rollout in a couple of years still to make such choices.

The fundamental choice seems to boil down to this - are you a donut or doughnut person? In much of the world a donut has a ring shape - hollow in the centre (center if we're following the spelling of donut!). Many believe they can deliver phase sync from "the edge of the core" or access layer. This would involve a layer of GPS PRTC / Boundary Clocks a minimal number of hops from the network edge - a phase sync "donut".

Here in the UK a doughnut is a disc shaped confection with no hole but a large amount of jam (jelly?) in the middle. In this case a smaller number of larger capacity and more resilient GPS PRTC devices would be deployed in the network core; disseminating phase sync through a network path that would probably demand full PTP awareness and on-path support.

Of course many factors in your network design could tip you from the donut to the doughnut - will you be deploying in largely legacy sites or is this a "green field" project; is it planned to have some or all of your traffic carried through a third party Managed Service; will you be using third party "dumb pipes" to transport your PTP packets for at least part of their journey to the edge?

Even if your LTE-A plans are a year or two away, you need to be thinking whether you are a donut or doughnut network. We at Chronos are developing "Phase Ready" tools to help carriers make these decisions, then implement and monitor them.

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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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Will it be Worth All the Pain?

Excellent piece from Graham Finnie, Chief Analyst, Heavy Reading in Light Reading - MWC14: What Are Telcos For? - giving a "from the outside" view of the Congress.

His conclusion, or nightmare scenario if you're a carrier, is that the network could just be a commodity that customers pay a bandwidth and "line rental" fee for. Services are already migrating away from the carriers (why SMS when you have WhatsApp and iMessage; why call with WhatsApp Voice and FaceTime Audio) and will continue to do so.

Of course most of the services running on your network are customer rich and income poor, and so the opportunity for you to sell underlying services is not a great prospect; and you're one step away from Internet Bubble 2.0 bursting, and this one won't be your fault! You'll still get the blame for teenage porn viewing and cyber-bullying though.

Even if charges for service providers on your network were viable, you have the spectre of Net Neutrality hanging over your head. This is described as "the founding principle of an open Internet" and without it would be "the end of the Internet". Net Neutrality though means all traffic must be treated equally - not a good start for revenue generation! And what politician is going to side with you against "the little guy"?

There will be no sympathy for your plight of course. You have a reputation (deserved or otherwise) of milking your customers over many years; exploiting the mobile cash cow in the way Independent Television companies did in the 60s and 70s. A license to broadcast was a license to print money.

So now you're rolling out scalable, flexible Carrier Ethernet backhaul; implementing the tight Traffic Engineering you'll need to deliver microsecond timing at the network edge for all the LTE-A services to come; paying for more and more spectrum and then having the cost of your "old" 2G and 3G spectrum increased; and all for the prospect of an affordable monthly fee!

And will you make anything from a worldwide simulcast of Paul McCartney live from the Cavern (or a TV set that looks like the Cavern)? And who's fault will it be if its not delivered perfectly to any device anywhere?

The future's bright......

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Is the "Phase Ready" message getting through - Part Two

We're engaged in some excellent work with several Wireless Backhaul manufacturers on PTP for phase and SyncE delivery at the moment. Fundamentally we have a simple message for those planning to roll out networks that require phase at the edge - if the radios have no On Path Support your network WILL NOT deliver microsecond phase coherence at the edge.

Interesting then that it looks like Phase is closer than some of us thought! We're currently assisting with the sync design of a Carrier Ethernet network that will require phase alignment at the edge, and frankly there is still a lot of engineering time and effort needed to find a solution that will deliver network requirements. Here's a good mantra to take with you in to any design exercise - "Don't think that On Path Support at every node ALONE will deliver adequate edge phase performance!"

We're also helping a Carrier with early planning of a Phase Ready network with lots of wireless backhaul that is probably three or four years away. Problem is their radio manufacturer currently does not have any product with On Path Support, but without this they can't engineer a network that will deliver! They're trying to be Phase ready but the market hasn't got there yet.

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LTE-B: Terrible TLA but coming to a device near you soon

One of the key upcoming technologies in the 3GPP world for some years now has been MBMS "Multimedia Broadcast Multicast Service" and latterly eMBMS "Evolved Multimedia Broadcast Multicast Service". This allows adjacent sites to transmit the same broadcast data, allowing devices an effectively higher data rate for streaming content. Promised but as yet undelievered, eMBMS requires microsecond (1us to 32us dependent on implementation) phase synchronisation between sites.

Three stories have appeared in short order to show this technology is becoming a reality. Last week Samsung announced they are working with Korea Telecom to deliver eMBMS services to their LTE subscribers. This was quickly followed by Verizon trialing "LTE Multicast" tied to the Super Bowl, and Telstra conducting the first stadium trial of "LTE Broadcast" at a T20 Cricket match at the MCG (well they call T20 Cricket but that's a subject I'm not going to touch here!).

I feel the marketeers won't be able to resist using LTE-B for this. Its even better than LTE-A!!



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Is the "Phase Ready" message getting through?

A couple of contrasting situations in big European Mobile Carriers demonstrates that the message is starting to get through - but there's still a lot of work to be done!

One major carrier who work closely with us at Chronos on sync and timing are busily engineering their edge network to be as symmetrical as possible to make sure their PTP for phase performance is a good as it can be. They currently have NO projects that require phase, although they use both SyncE and PTP for edge frequency.

I also heard this week of a carrier that committed only last year to a large rollout of Ethernet Microwave radios for backhaul, but selected a platform that cannot support PTP on path support. This is a supported product and so no criticism on selecting this for the project they had at the time, but they are now considering a trial of LTE-A requiring phase at the edge via a backhaul pipe that will impair phase performance with no upgrade path to help!

It really does make sense to think of the phase supporting future when considering frequency only projects today. This future is not as far away as you may think, and is likely to be in the lifetime of equipment you are currently considering for use.

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And You Thought Phase Would Be Tough?

I must admit that over the last year or so I thought, as far as PTP is concerned, that "frequency is done". From the early development days of PTP for frequency we went from "you can't trust it over more than 3 hops" to moving frequency through long networks of switches and microwave links without batting an eyelid. In this context the crusade to ask "Is Your Network Phase Ready?" began.

Intriguing then that I know of a situation TODAY where a Gateway device from a very reputable manufacturer with embedded PTP client is incapable of delivering adequate FREQUENCY to Node Bs after only a few network hops with even moderate traffic levels. This leads me to reinforce a view I've spoken about before - just because something is PTP aware doesn't mean it works!

We're seeing the drive today for full on path support in sync networks delivering phase to the edge, and people wanting to play in the Small Cells space (like Microwave Backhaul providers)  realise that they will have to interact with these PTP packets and will all be implementing a variety of boundary and transparent clock type solutions to do so.

I am still very much of the opinion then that your sync network should be INDEPENDENT of your transport network, or at least independently monitored and qualified for time and timing performance.

If you can't move adequate phase performance to the edge of your network you WILL have a negative impact on your customers' experience. Can you trust this key performance element to the people who supplied and support your transport network?

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Small Cells World Summit Report - David Chambers

Good overview of the Summit from Think Small Cells's David Chambers HERE. Particular interest for me in the embedded video of interviews David conducted is Todd Mersch of Radisys talking about the two key areas that will be exploited from LTE-A. Todd can of course speak for himself but the two areas he identified - Carrier Aggregation (CA) and SON / Interference Mitigation - will have stringent phase sync requirements!

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First Small Cells Backhaul Summit a success

Just back from the Small Cells World Summit and decided to sit in on the whole of the inaugural Backhaul Summit track. Had to sit on my hands at times to not ask the "what about phase sync?" question, but I was pleasantly surprised that there was some awareness at least of the challenges coming our way.

Some very interesting battles to come in the sub 6GHz non line of sight area if the debates at this summit were anything to go by!

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Tested Against What?

There was an interesting question from the floor during our Phase Ready Seminar on Wednesday; basically questioning the need for independent benchmarking and monitoring of phase in a network when manufacturers are building in an array of synchronisation performance statistics into their PTP Aware Switches and Routers.

From our perspective the response is simple - what are these statistics actually measuring and what are they measuring against? Of course in day to day operations the data available from within the end to end network management platform will be a key to deciding what actions if any are required should a particular set of circumstances arise. However, we think that, at the very least, these performance metrics should be calibrated against a set of independently verified and traceable measurements to put them in greater context.

This is why we are working with several equipment vendors to integrate SyncWatch into their EMS and OSS systems.

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Is Your Backhaul Sync Available to You?

PDH and SDH/SONET core networks made life pretty easy for the NodeB that needed 50ppb timing for the Air Interface. The transport technology inherently carried traceable time, and this was available via the T1/E1 interface that carried your traffic. This timing quality was available whether this core network was yours or provided by a third party!

Now we're looking to a future of microsecond sync at the edge, and planning for how we get that level of synchronisation out there. Some of the backhaul technologies being mooted for Small Cells are TDD based and therefore need good synchronisation themselves for optimal performance. FTTx and GPON for example in the fixed category, and several TDD radio systems whether point to point or point to multipoint.

The questions that strike me here are:

What level of synchronisation is needed for these transport technologies?

Is this sufficient for your phase synchronisation needs?

Can this technology carry your own timing (PTP packets for example) without compromising performance?

Can you trust your network performance to a third party?

Is this sync available to you as the user anyway?

Start to get answers to some of these questions,or just ideas on what sort of questions you need to ask, at our free "Is Your Network Phase Ready?" Seminar at Kings Place on Wednesday May 8th.

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Phase Ready - Why Now?

Why is it important to consider phase synchronisation at the network edge when, at least here in the UK, you're only just rolling out your LTE Macro layer?

A valid question, but you may well also be rolling out 3G Small Cells for indoor coverage in public spaces and enterprises,data offload, or Outdoor Event systems. Choices that make perfect technical and economic sense for these systems may well come back to haunt you if you don't take heed of the future (and not so far flung future) phase requirements your network will have.

Take backhaul technologies for example. You will of course find backhaul that's perfectly suited to your requirement now; perhaps getting SyncE right out to the Small Cells to give great frequency sync for the Air Interface. But is this backhaul phase ready? When you need to overlay this great frequency network with PTP packets to get microsecond sync to Small Cells, will this backhaul deliver the timing performance you need?

Decisions taken now for Small Cells need to take account of the requirement you WILL have for phase when you're delivering LTE-A services. Think smart and you won't need to rip out your two year old backhaul network because it wasn't future proof.

Our "Is Your Network Phase Ready" seminar at Kings Place on May 8th has a session "Small Cells Backhaul - the “Wild West” Explained". 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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