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Sync – It’s Not Just for 5G! The Role of Network Synchronization Beyond Mobile Transport

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Jon Baldry

July 29, 2021
By Jon Baldry
Director, Metro Networking

The migration to 5G is undoubtably one of the major trends that is currently driving network upgrades across many telecoms networking domains, including the underlying mobile transport network. As we discussed in the first three blogs in this series, this migration is driving a refocusing of attention on synchronization distribution within optical transport networks and higher performance goals to support the tighter requirements of 5G.

Synchronization distribution modernization to support 5G in transport networks is driving a rethink in global navigation satellite system (GNSS) usage strategies, and it requires a focus on the impact that all elements of the optical network have on synchronization distribution as well as a complete end-to-end strategy. But 5G isn’t the only application that is driving high-performance synchronization within optical networks. We’ll discuss these other non-5G applications in this blog, which is the last in this current series of sync-related blogs.

5G is naturally the focus for most current synchronization distribution discussions as it is one of the most challenging applications and very timely due to 5G rollouts. Beyond 5G we have numerous other applications that require some form of synchronization or timing distribution utilizing the same mechanisms that we use for 5G. These cover many industrial and business applications as well as some network migration applications.

Many applications, such as financial trading, scientific collaboration, or distributed control applications, require secure and accurate time stamping and synchronization between network nodes. This can be achieved through each location using GNSS, although as we see in mobile networks, there is a trend toward using the interconnecting transport network as either a backup or primary source of timing distribution to protect against GNSS interference. Looking at industrial manufacturing, it is anticipated that advances in manufacturing techniques will drive the need for tighter coordination between sites that in turn will further drive the need for synchronization into the interconnecting transport networks.

Another networking use case that can benefit from advanced synchronization techniques is video and digital audio broadcast (DAB) distribution networks. Network operators have found that challenges in the application layer caused by poor synchronization between the video/DAB server and other networking devices such as the cable modem termination system (CMTS) can be resolved by enabling synchronization capabilities, such as 1588v2, within the underlying packet-optical transport network. Using a combination of telecom boundary clock (T-BC) and telecom transparent clock (T-TC) within the transport network, these operators can preserve more of the overall timing budget for other elements of the DAB application.

One of the most interesting applications for phase synchronization is the introduction of ultrafast synchrophasor technology in electrical power distribution networks. Electrical power networks have always needed phase synchronization within the electrical power lines themselves to ensure that the power distribution network operates efficiently and robustly.

But the parallel supervisory control and data acquisition (SCADA) networks used to monitor and maintain these power networks didn’t require any synchronization until the introduction of synchrophasors. These synchrophasors enable power utility companies to actively monitor the power levels and the phase of the power lines in real time through the use of phasor measurement units (PMU) that report the power level and phase in time-stamped messages. This requires the parallel datacoms network to synchronize these PMUs with frequency, phase, and time of day in a very similar way to 5G time-division duplex (TDD) networks.

Synchrophasor technology was invented over 30 years ago but has only recently started to be rolled out in power distribution networks. The most common use of the technology is more accurate detection of the exact location of a power cable cut, enabling the power utility to locate network issues such as power line breakages more quickly. In one very interesting case, San Diego Gas and Power is even using this technology to detect power line breakages and turn off power in the impacted section before the broken lines hit the ground to reduce the chances of these lines starting a wildfire.

This power utility use case is also a good example of another network migration that is driving the need for advanced synchronization, namely TDM migration. Here the need for synchronization is driven by end-of-life issues with older networking hardware rather than the end application itself. Many utility companies have extensive monitoring and datacoms networks covering their facilities and infrastructure that drives a relatively fixed volume of traffic when compared to the rapidly growing traffic seen in telecoms networks. Their existing SDH/SONET networks continue to serve their needs relatively well, but the SDH/SONET hardware is often reaching end of life and is expensive, and increasingly difficult, to maintain.

As these utility companies and other network operators with older SDH/SONET infrastructure look to migrate to newer Ethernet hardware, they have the challenge of maintaining older TDM services, such as E1 or T1 services, to support their SCADA devices. To enable these older TDM services over newer Ethernet infrastructure, we need to implement TDM circuit emulation over the new packet-optical network. We also need to use SyncE-based frequency synchronization to create a common clock within the network and differential clock recovery (DCR) to enable individual TDM services to maintain their own synchronization between the two service end points. Overall, the combination of these capabilities enables the network operators to replace the older SDH/SONET network with a newer packet-based transport network while maintaining the older TDM services.

In summary, while 5G is understandably the current focus for a lot of network synchronization discussions, there are plenty of applications beyond 5G that require or can benefit from the same mechanisms and high performance that 5G is driving into transport networks. As we move to an increasingly advanced society with ever more automation and remote management of devices, it is likely that the range of applications requiring or benefiting from high-performance synchronization delivery within the transport network will only increase.

For those readers that want to dive into this topic in more detail, our Synchronization Distribution in 5G Transport Networks e-book provides a detailed overview of synchronization distribution challenges and standardization along with an end-to-end synchronization distribution strategy that meets the demanding requirements that 5G, and this range of other applications, is driving into optical networks.