Resilient Timing for Critical National Infrastructure

Critical infrastructure requires precise timing to operate. This reliance makes the infrastructure vulnerable to disruptions in timing that can be either intentional or unintentional. Intentional disruptions can be caused by GNSS jamming or spoofing or network attacks.. Unintentional disruptions are usually caused by equipment failures or acts of nature.

Back in April 2022, Alliance for Telecommunications Industry Solutions (ATIS) hosted a webinar on this topic, a precursor to the Annual Workshop on Synchronization and Timing Systems (WSTS). The webinar featured top industry experts delivering insight into the latest techniques for adding resilience and robustness to timing infrastructure. It covered the most critical topics in timing resilience, including:

• Redundancy
• Holdover
• Management
• Monitoring
• Alternative reference time sources

Examples address networks used for critical industry applications such as:

• Power grids
• Telecommunications
• Finance systems
• Broadcast/media

The video of the webinar as follows:

Experts participating in the webinar and their presentations are as follows:

• Introduction – Marc Weiss, PhD
• Redundancy and Monitoring – Doug Arnold, Principal Technologist, Meinberg
• Solutions for Backup Resiliency – David Chandler, Product Line Manager, Microchip
• Diversity of Sources (Beyond GNSS) – Anand Ram, Vice President, Business Development, Calnex
• An Example of Resilience and Assurance – Nino De Falcis, Senior Director of Business Development, Oscilloquartz

Please feel free to share other useful resources on this topic in comments.

Related Posts: 

• Telecoms Infrastructure Blog: Synchronization for 5G - Requirements, Solutions & Architecture
• The 3G4G Blog - CWHeritage Talk: The History of Synchronization in Digital Cellular Networks
• The 3G4G Blog: 5G Synchronisation Requirements 

5G Synchronisation Requirements

5G will probably introduce tighter synchronization requirements than LTE. A recent presentation from Ericsson provides more details.

A nice presentation by Ericsson from #WSTS2018: Sync in 5G: What is really needed? - https://t.co/X3XIokELpe pic.twitter.com/6du5ezFfqE

— 3G4G (@3g4gUK) July 17, 2018

In frequencies below 6GHz (referred to as frequency range 1 or FR1 in standards), there is a probability to use both FDD and TDD bands, especially in case of re-farming of existing bands. In frequencies above 6GHz (referred to as frequency range 2 or FR2 in standards, even though FR2 starts from 24.25 GHz), it is expected that all bands would be TDD.

Interesting to see that the cell phase synchronization accuracy measured at BS antenna connectors is specified to be better than 3 μs in 3GPP TS 38 133. This translates into a network-wide requirements of +/-1.5 microseconds and is applicable to both FR1 and FR2, regardless of the cell size.

Frequency Error for NR specified in 3GPP TS 38.104 states that the base station (BS) shall be accurate to within the following accuracy range observed over 1 ms:
Wide Area BS → ±0.05 ppm
Medium Range BS → ±0.1 ppm
Local Area BS → ±0.1 ppm

The presentation specifies that based on request by some operators, studies in ITU-T on the feasibility of solutions targeting end-to-end time synchronization requirements on the order of +/-100 ns to +/-300 ns

There is also a challenge of how the sync information is transported within the network. The conclusion is that while the current LTE sync requirements would work in the short term, new solutions would be required in the longer term.

If this is an area of interest, you will also enjoy watching CW Heritage SIG talk by Prof. Andy Sutton, "The history of synchronisation in digital cellular networks". Its available here.

#CWHeritage Talk: The History of Synchronization in Digital Cellular Networks

CW (a.k.a. Cambridge Wireless) held a very interesting event titled 'Time for Telecoms' at the Science Museum in London. I managed to record this one talk by Prof. Andy Sutton, who has also kindly shared slides and some other papers that he mentions in his presentation. You can also see the tweets from the event on Twitter.

The video playlist and the presentation is embedded below.

The history of synchronisation in digital cellular networks from 3G4G

The papers referred to in the presentation/video available as follows:

• Martin Kingston: The need for Synchronisation in Telecommunications
• Charles Curry: Time from the Sky
• Sébastien Jobert & Kenneth Hann: Synchronisation and Time Distribution in Modern Telecommunications Networks
• Tommy Cook & Tim Frost: Stepping up to the Challenge on Tighter Time Accuracy.
• Andy Sutton: The history of synchronisation in digital cellular networks

5G and Evolution of the Inter-connected Network

While there are many parameters to consider when designing the next generation network, speed is the simplest one to understand and sell to the end user.

Last week, I did a keynote at the International Telecom Sync Forum (ITSF) 2015. As an analyst keynote, I looked at how the networks are evolving and getting more complex, full of interesting options and features available for the operator to decide which ones to select.

There wont just be multiple generations of technologies existing at the same time but there will also be small cells based networks, macro networks, drones and balloons based networks and satellite based networks.

My presentation is embedded below. For any reason, if you want to download it, please fill the form at the bottom of this page and download.

Just after my keynote, I came across this news in Guardian about 'Alphabet and Facebook develop rival secret drone plans'; its an interesting read. As you may be aware Google is actively working with Sri Lanka and Indonesia for providing seamless internet access nationally.

It was nice to hear EE provide the second keynote which focused on 5G. I especially liked this slide which summarised their key 5G research areas. Their presentation is embedded below and available to download from slideshare.

5G: The Future of Mobile Communications - EE from Zahid Ghadialy

The panel discussion was interesting as well. As the conference focused on timing and synchronisation, the questions were on those topics too. I have some of them below, interested to hear your thoughts:

• Who cares about syncing the core? - Everything has moved to packets, the only reason for sync is to coordinate access points in wireless for higher level services. We have multiple options to sync the edge, why bother to sync the core at all?
• We need synchronisation to improve the user’s experience right? - Given the ever improving quality of the time-bases embedded within equipment, what exactly would happen to the user experience if synchronisation collapsed… or is good sync all about operators experience?
• IoT… and the impact on synchronisation- can we afford it? - M2M divisions of network operators make a very small fraction of the operator’s revenue, is that going to change and will it allow the required investment in sync technology that it might require?

Challenges in the future 'Network of Networks'

Came across this paper from Dec. 2000 recently. Its interesting to see that even back then researchers were thinking about multiple networks that a user can have access to via handovers. Researchers nowadays think about how to access as many networks as possible simultaneously. I call is Multi-stream aggregation (MSA), some others call it Multi-RAT Carrier Aggregation (MCA) and so on.

If we look at the different access technologies, each has its own evolution in the coming years. Some of these are:

• Fixed/Terrestrial broadband: (A)DSL, Cable, Fiber
• Mobile Broadband: 3G, 4G and soon 5G
• Wireless Broadband: WiFi
• Laser communications
• LiFi or LED based communications
• High frequency sound based communications 

Then there could be a combination of multiple technologies working simultaneously. For example:

• Broadband Access via Integrated Terrestrial & Satellite Systems (BATS)
• LTE-U / LTE-LAA

And the handover has to be seamless between different access technologies. For example:

• Seamless handovers between cellular and WiFi and vice versa.

There has been an interest in moving on to higher frequencies. These bands can be used for access as well as backhaul. The same applies for most of the access technologies listed above which can work as a backhaul to enable other access technologies.

While planned networks would be commonplace, other topologies like mesh network will gain ground too. Device to device and direct communications will help create ad-hoc networks.

While the current networks are mostly stationary, mobile networks will also become common. Opportunity Driven Multiple Access (ODMA) or Multihop Cellular Networks (MCN) would help devices use other devices to reach their destination. Non-standardised proprietary solutions (for example Firechat) will become common too. Security, Privacy and Trust will play an important role here.

Satellite networks, the truly global connectivity providers will play an important role too. While backhauling the small cells on planes, trains and ships will be an important part of satellite networks, they may be used for access too. Oneweb plans to launch 900 micro satellites to provide high speed global connectivity. While communications at such high frequencies mean that small form factor devices like mobile cant receive the signals easily, connected cars could use the satellite connectivity very well.

Samsung has an idea to provide connectivity through 4,600 satellites to be able to transmit 200GB monthly to 5 Billion people worldwide. While this is very ambitious, its not the only innovative and challenging idea. I am sure we all now about the Google loon. Facebook on the other hand wants to use a solar powered drone (UAV) to offer free internet access services to users who cannot get online.

As I mentioned, security and privacy will be a big challenge for devices being able to connect to multiple access networks and other devices. An often overlooked challenge is the timing and sync between different networks. In an ideal world all these networks would be phase and time synchronised to each other so as not to cause interference but in reality this will be a challenging task, especially with ad-hoc and moing networks.



I will be giving a keynote at the ITSF 2015 in November at Edinburgh. This is a different type of conference that looks at Time and Synchronisation aspects in Telecoms. While I will be providing a generic overview on where the technologies are moving (continuing from my presentation in Phase ready conference), I am looking forward to hearing about these challenges and their solutions in this conference.

Andy Sutton (Principal Network Architect) and Martin Kingston (Principal Designer) with EE have shared some of their thought on this topic which is as follows and available to download here.

'The Future Inter-connected Network' and Timing, Frequency & Phase requirements

I had the pleasure of doing a keynote at PhaseReady 2015 in London today. My presentation is embedded below along with some comments, followed by tweets some of which I think are important to think about. Finally, I have embedded a video by EE and Light Reading which was quoted and maybe its important in the context of this event.

The Future Inter-connected Network from Zahid Ghadialy

My main focus during this presentation has been on how the networks have evolved from 3G days with the main focus (unconsciously) on speeds. While the networks are evolving, they are also getting more complex. The future ecosystem will consist of many Inter-connected (and in many cases inter-operable) networks that will work out the requirements in different situations and adapt to the necessary network(technology) accordingly.

An example of today's networks are like driving a manual car where we have to change gears depending on the traffic, speed required and fuel efficiency. Automatic cars are supposed to optimise this and achieve the best in all different cases. The future inter-connected networks should achieve the best based on the requirements in all different scenarios.

While it is easy to say this in theory, the practical networks will have many challenges to solve, including business and/or technical. The theme of the conference was timing, frequency and phase synchronisation. There are already challenges around them today, with the advanced LTE-A features. These challenges are only going to get bigger.

The following are the tweets from the day:

Finally, here is the link to video referred to in the last tweet. Its from last year but well worth listening.

Timing Accuracy and Phase Performance Requirements in LTE/LTE-A/4G

Nice quick summary videos from Chronos.



If you are interested in learning more on this topic or discussions, I would recommend joining the Phase Ready Linkedin group.