Operator views on 5G transport slicing and synchronization

5G-Advanced will introduce not just greater capacity but also new capabilities. In fact, many of the advances and technologies most associated with 5G — such as ultra-low latency use cases and network slicing — will be enhanced by 5G-Advanced and beyond. Network operators are preparing their transport networks for the new phase.

In February, Heavy Reading conducted the fourth iteration of its annual 5G Transport Market Leadership Survey with project partners Ericsson, Fujitsu and Nokia. The 2023 survey attracted 87 qualified network operator responses from around the world who shared their views on transport deployment issues and timelines, fronthaul networks and RAN centralization, routing and synchronization, and 5G edge connectivity.

This blog is the final installment in the three-part series highlighting the key findings from the study. It focuses on trends in network slicing and synchronization.

Network slicing

One of the biggest differentiators in 5G compared to previous mobile generations is the ability to use network slicing to offer different types of services to multiple customers — all sharing the same operator infrastructure. Slicing involves the RAN, the core and the transport network and requires coordination across these domains to ensure end-to-end service requirements are met.

Just about half of the operators surveyed have plans for network slicing. Among those with slicing plans, 28% report that initial network slicing deployments have already begun. An additional 33% of those surveyed expect initial deployments to occur this year.

Multiple technologies exist for slicing, including hard slicing options, such as ODU-Flex (short for flexible optical data unit), and soft slicing options, such as IP/MPLS and segment routing. Operators surveyed expect a mix of transport slicing, led by soft slicing using IP/MPLS (selected by 56% of the group) and hard slicing using ODU-Flex (picked by 51%). A mix of hard/soft slicing enables better network utilization to help reduce costs while providing the service flexibility and scale needed to address growing demand and support a broad range of use cases.

As a next-generation technology for soft slicing, segment routing also shows strong promise. Selected by 49% of operators, it ranks third among transport slicing options in the survey. There are real-world examples as well. Both SingTel and NTT DOCOMO have announced trials using segment routing for network slicing, as discussed during the related webinar. Segment routing offers advantages in terms of better scale, reduced control plane signaling and alignment with software-defined networking (SDN) control.

Which technologies will your organization use for transport network slicing?

Figure 1:
(Source: Heavy Reading, 2023)

Timing & synchronization

The move from 4G to 5G radio technologies introduces new challenges and requirements in delivering synchronization over packet transport networks. These challenges include the greater use of time division duplex (TDD) spectrum requiring phase/ timing distribution, cell site densification (particularly at street level) and fronthaul connectivity requirements, among others.

44% of the survey group identified plans to implement network-based synchronization by 2025. For these operators, multiple factors drive the need, especially better visibility into synch/ troubleshooting per hop and improved synch source availability, with both factors selected by 47% of the respondents.

Better synch operations, administration and maintenance (OAM) and troubleshooting tools are crucial because network operators must meet stringent frequency and phase/ time synchronization requirements in 5G mobile transport networks. To succeed, they need new tools that will enable them to simplify and automate the configuration, provisioning and management of the synchronization layer network.

What are the primary drivers for using network-based synchronization?

Figure 2:
(Source: Heavy Reading, 2023)

Timing profiles are a hot topic in 2023, as many operators are concerned that partial timing support — in which only some nodes have network-based timing capability — may be insufficient for 5G moving forward. The issue is that partial timing cannot support the tens-of-nanoseconds timing accuracy that may be needed. Being the most accurate, full timing support is ideal, but it may require costly upgrades of nodes throughout the entire network. Assisted partial timing support is a hybrid approach that uses satellites to calibrate the network timing prior to the satellite signal becoming unavailable.

Operator preferences for different timing profiles vary by xHaul segment, according to the survey. 61% of respondents see the greatest need for full timing support in fronthaul. Given that in fronthaul, the ITU recommends Class C boundary clocks with a maximum two-way time error of 30ns, full timing support may be the only option.

For backhaul, the ITU recommends Class A or B accuracy, which provides more margin for timing error. A plurality of operators surveyed (42%) indicated they would use partial timing support for backhaul, with an additional 13% expecting assisted partial timing. Still, 39% expect full timing support.

Which of the following timing profiles will your organization implement?

Figure 3:
(Source: Heavy Reading, 2023)

Throughout the 2023 5G Transport Market Leadership Survey, "tools in the toolbox" is a recurring theme. This theme holds true for network slicing and timing and synchronization, as operators will choose among many options and use what makes the most sense to them for their specific needs. In 5G transport, one size does not fit all.

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This blog is sponsored by Nokia.