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IMT-2030, or 6G in common parlance, is not expected to be commercially available until the start of the next decade. Neither has an industry consensus emerged as to what exactly the ‘next G’ will look like.
Even so it’s not too soon for the International Telecommunications Union (ITU), the specialized United Nations agency for information and communication technologies, to engage with network operators to better understand their requirements for transport and access networks that will support 6G (and 5G advanced) radio as specified by 3GPP. By doing so, ITU aims to lay the groundwork for new work items and produce technical reports and ‘Recommendations’ that might help guide the IMT-2030 direction of equipment suppliers, research bodies and standards developing organizations (SDOs).
This was the purpose of a recent four-hour ITU workshop held in Montreal, Canada. Organized by Study Group 15 (SG15), the workshop – “The Evolution of Transport and Access Networks to Support IMT 2030/6G” – brought together technology experts from AT&T, BT, China Mobile, China Unicom, NTT and Telus.
SG15 operates within the purview of the ITU Telecommunication Standardization Sector (ITU-T) and is responsible for standards development across transport, access and home networks. Its aim is to enable evolution towards intelligent optical networks. The ITU Radiocommunication Sector (ITU-R), which plays a major role in the management of radio-frequency spectrum and satellite orbit resources worldwide, works in parallel with ITU-T.
IMT-2030 soundings start early
Glenn Parsons, Chair of ITU-T SG15 – and Principal Standardization Advisor at Ericsson Canada – acknowledged in his opening remarks at the Montreal workshop that ITU-T wanted to start earlier in the ITU-R cycle for IMT-2030 than it did for IMT-2020/5G. SG15 held its 5G workshop to identify IMT-2020 optical network requirements in October 2017, which was less than two years before the first large-scale commercial 5G networks were launched in South Korea.
Parsons told Light Reading that SG15 was nonetheless sensitive to the view held by some mobile network operators of not yet wanting to contemplate 6G, since they have either just completed 5G buildout or are in the early throes of 5G advanced. “It’s why we included support for 5G advanced in the architecture and requirements for IMT 2030/6G transport network support,” he said.
Topics covered by the Montreal workshop were varied and given the nascent nature of 6G, inevitably speculative (albeit based on current trends in optical network technologies).
“The goal was to get an initial view to identify the differences between the topology of the IMT 2030/6G network and the topology of current 5G network from a transport perspective,” explained Parsons. “The 5G network saw significant focus on the fronthaul transport network, but what will 6G bring? Besides expected new link capacity and latency requirements, what are the requirements for transport network support of the energy efficiency objectives of IMT2030/6G?”
Paul Doolan, who helped organize the workshop and is Chair of SG15’s Working Party 2, which is focused on optical technologies and physical infrastructure, lauded the “creative thought” shown by the presenters in Montreal.
“Dr. Han Li [China Mobile] talked about satellites, Dr. Shikui Shen [China Unicom] about ‘endogenous capabilities’ and optical networking between data centres, cities, undersea and in space, and Dr. Nakajima [NTT] talked about all-photonic networks [APN],” Doolan told Light Reading. “IMT2030/6G is a work in progress and our colleagues are energetically contributing to that and helping guide what SG15 can and should do.”
Unsurprisingly for Doolan, who is also senior consulting expert for optical standards at Huawei’s Hong Kong Research Center, power consumption emerged as a major concern from the Montreal event. “We heard from the workshop that RAN consumes 50% of the energy used in the mobile network, so meeting the broader IMT2030/6G ubiquity goal of connecting the unconnected means we have to be ‘greener’ and ‘more efficient’ – which were key themes in two of the presentations – if we are not to destroy operators’ balance sheets and, much more importantly, not burn down the planet,” he said.
Parsons added that the workshop threw the spotlight on network management and automation: “We wanted to explore the benefits of integrating the management of the transport and access network, and how AI/ML might make this simpler.”
An IMT-2030 perspective from China Mobile
“IMT-2030 transport will need a lot of evolution or revolution [when compared with IMT-2020],” said Dr. Han Li, Chief Expert at China Mobile, who gave a detailed presentation on possible 6G transport and access network requirements at the Montreal workshop.
Drawing on a range of 6G usage scenarios outlined by ITU-R in December 2023, Han speculated that the 6G fronthaul eCPRI (enhanced Common Public Radio Interface) will need to support 100Gbps links, and that 6G femtocells will need 50G PON backhaul (with the caveat they have lower latency and greater network slicing capability than is possible with today’s 50G PON equipment).
Han further noted that the integration of sensing with communications, where networks can identify stationary and moving objects – and one of the ITU-R 6G usage scenarios – will need smart management and synchronization of radio signals at the control layer from different base stations, something which is difficult within an IMT-2020 architecture.
Another 6G novelty and challenge, predicted Han, will be in the core network. “In 5G the CP [control plane] and the UPF [user plane function] are separated, with the CP centralized and the UPF deployed on demand,” he said. “[To meet business customer requirements, we think] the 6G core network will evolve towards distributed autonomy by introducing ‘small cloud units’ that integrate both UPF and CP and will be widely deployed.”
Han, as Doolan highlighted, was also keen to examine 6G space-air-ground integration. “It is essential to explore the inter-satellite optical-layer networking architecture and key technologies that accommodate the highly dynamic satellite network topology,” he said.
Parsons agrees with many aspects of China Mobile’s 6G vision. “IMT-2030 is likely to add additional high frequency spectrum that requires the transport and access network to support significantly higher capacity and throughput compared to IMT-2020,” he said. “High frequency spectrum will also drive a need for more cells for this to be useful to the end users. which will push the densification and need for more transport interconnection.” Parsons also flagged the need for “tight synchronization” to support distributed MIMO for uniform coverage, high peak rate and higher capacity.
“There will also be a drive to have standards that enable lower cost optics at the required speeds, while also ensuring synchronization accuracy is not compromised,” he added. “Many operators have an access network that they would like to leverage but this is a challenge even for IMT-2020. New access technology, perhaps moving from IM-DD [intensity modulation-direct detection] to coherent, will be focused on supporting 6G use cases.”
Optical network evolution towards 2030
“SG15 has been actively engaged in shaping the future of optical telecommunications standards for decades and this will continue,” remarked Parsons. Looking ahead to the next 5-10 years, he says that SG15 will likely focus on several key areas, including: next-generation OTN (which may include an increased focus on energy-efficient optical network technologies); fiber evolution (a look at hollow-core fiber and the introduction of space division multiplexing to drive higher capacity with better efficiency); and network automation and intelligence.
“SG15 is already planning to focus on standards for network automation, intelligent control and management of optical transport networks, leveraging technologies such as AI, ML and software-defined networking to improve end-to-end performance guarantees and energy efficiency,” said Parsons.
Doolan believes optical network evolution will be important going forward because of bandwidth, power, cost, latency and resilience considerations, and thinks it likely too that IMT-2030 will require a new generation of optical network technologies and standards and that SG15 is already seeing proposals of that sort.
“The Montreal meeting already suggested we form a focus group to study, communicate and coordinate on these matters, and Dr. Li even suggested a name: International Optical Telecommunications towards 2030 (IOT2030)”, added Doolan. “I expect we’ll see more interest in this suggestion as we start the next study period.”
Ongoing collaboration and coordination with various industry stakeholders, such as OIF (Optical Internetworking Forum) and OpenROADM – a collaborative effort between carriers and vendors – as well as SDOs (including IEC and IEEE 802) and other ITU-T/ITU-R study groups, underpins SG15 work. “It’s needed to ensure alignment and promote interoperability of optical telecommunications solutions,” stressed Parsons.
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