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13 December 2018

Nokia and China Mobile partner on Open RAN architectures for 5G

While the leaders of the USA and China rant and rave at one another, western companies continue to work closely with those in China, aware that 5G will be a global platform, and will only achieve its full potential with input from as many organizations as possible.

In the past, Chinese companies have been associated with proprietary technologies and closed ecosystems, but in the run-up to 5G, it has been China’s operators, especially China Mobile, which have been a driving force behind open, disaggregated and virtualized RANs. China Mobile’s vision of the Cloud-RAN, set out early this decade, was over-ambitious and too radical for most operators to emulate. But it laid down the gauntlet to the network hardware industry – the new RAN needs to have a completely different cost base, and the flexibility to support many future use cases with different network behaviors, otherwise it will be hard to justify a significant new wave of investment.

Since then, China Mobile has pushed other aspects of the nascent open network ecosystem – sometimes, it seemed, against its true instincts. Open source has been hard for Chinese operators to adapt to, yet the country’s largest MNO submitted its developments in management and orchestration (MANO) for virtual networks to the open community, and that was subsequently merged into the ONAP (Open Network Automation Protocol) initiative along with AT&T’s ECOMP.

The latest development sees China Mobile working with Nokia to develop open RAN interfaces, which will drive a more open 5G supplier ecosystem. This is the goal of most operators, which believe there must be more competition and innovation in a supply chain that is confined, effectively, to five vendors (and only three in countries where Huawei and ZTE are barred from pitching for 5G network deals).

MNOs are supporting disruptive start-ups, directly or through alliances like the Facebook-led Telecom Infra Project (TIP), but most of these are far away from being ready to supply critical, prime-time networks. So operators are equally keen to put pressure on their traditional, largely trusted vendors to adapt to the new norms of open, multivendor, software-driven platforms, which will encourage WiFi-like price competition.

Nokia has been the most willing, of the big four, to make these changes. Along with Samsung, it has supported several open industry initiatives in the RAN, such as the AT&T-inspired xRAN (merging with the Cloud-RAN Foundation to form the Open RAN Consortium, hosted by the Linux Foundation). This, like Facebook TIP’s vRAN Fronthaul and OpenCellular efforts, looks to define common specifications for the link between radio heads and basebands in a disaggregated network, which will increasingly be virtualized too.

Its collaboration with China Mobile focuses on use cases for the ORAN platform. The Finnish vendor has signed an agreement with the China Mobile Research Institute (CMRI) to work on optimizing 5G networks for a range of practical use cases, based around an open, interoperable and multivendor RAN.

Their work will initially address some of the key emerging service requirements for the new mobile networks, which the partners listed as:

  • A decentralized, multivendor architecture in which the central unit controls several remote distributed units, and most baseband functions are centralized and virtualized on cloud infrastructure. This architecture will support real time and non-real time processing capabilities, the former requiring more physical and virtual network functions (VNFs) to be located at the cell site or edge node.
  • Jointly specified open RAN interfaces between multivendor components, such as the fronthaul interface connecting the central unit to the remote radio heads.
  • Smart radio intelligence control using advanced network analytics.
  • Commercial off-the-shelf (COTS) hardware equipment.

“By optimizing multivendor network interworking we will be able to access network intelligence and use end-to-end data analytics and machine learning to support the delivery of innovative new consumer and industry services in the 5G world,” said Zhiqiang Yang, a VP of CMRI.

“5G will enable new use cases with a wide variety of service level requirements,” said Tommi Uitto, president of mobile networks at Nokia. “An optimized and open end-to-end network will enable the levels of automation and artificial intelligence for

the network to support with high performance any demands placed on it.”

The shift to examine real world use cases shows how these new architectures are creeping closer to the commercial mainstream. Nokia and China Mobile have been working on Cloud-RAN together for some years and in August, they announced a live deployment of a disaggregated LTE network.

The companies said that the trials of this network showed that a Cloud-RAN could achieve the same throughput, latency and service set-up success rate as a traditional physical RAN, and remained stable. The main aim of that trial was to verify that the disaggregated platform would be able to support the division of real time processes at the cell site, and non-real time functions in the data center (where the consolidation of many base stations, and the resulting economies of scale, will deliver considerable cost savings for non-time critical applications).

Although the partnership is initially concerned with China Mobile’s bid for a more cost efficient and flexible RAN – and a way to transition smoothly to 5G while preserving 4G investments – the companies expect to submit some of their developments to open industry alliances to accelerate progress towards a common, affordable platform for open, virtualized RANs.

Of course, it can be argued that Nokia is shooting itself in the foot by actively encouraging architectures which will rob it of a lucrative business in specialized hardware and proprietary platforms. But the vendor has clearly taken a decision to lead the transition to the new network, rather than resisting it and finding itself left behind during a wave of 5G contracts in the early 2020s.

Although some 5G network deals have already been awarded – including a $3.5bn contract which Nokia won with T-Mobile USA this year – the bigger wins are likely to come when operators start to virtualize their RANs. For many, this will go hand-in-hand with 5G Standalone, which then requires investment in the 5G core.

For most, these major architecture changes are a few years away, and they will not boost the traditional RAN equipment market – in fact, they are designed to reduce capex and opex by virtualizing as many digital baseband functions as possible on commodity servers and white box switches, leaving stripped-back radio antenna units at the cell site.

So Nokia is a turkey voting for Christmas when it comes to supporting efforts to develop an open fronthaul interface – but will aim to offset the loss of traditional revenue and margin with higher market share in the new networks, and the ability to target new 5G opportunities such as wholesale and neutral host deployers.

There are several projects looking to create standardized fronthaul specifications. The IEEE’s Ethernet 1914 TSN (Time Sensitive Networking) standard will underpin many of these.

The ORAN Alliance is one of the most influential. Its predecessor, the xRAN Forum, announced its first set of specs, the xRAN Fronthaul Specification Version 1.0, in April, and then followed up with Release 2.0 to fill in some of the gaps in that initial interface, particularly a weakly defined management plane. That included the xRAN Fronthaul Control, User and Synchronization (CUS) Plane Specification Version 2.0 and the xRAN Fronthaul Management Plane (MP) Specification Version 1.0.

The second version of the CUS plane spec includes support for two radio categories, A and B, to enable both simple and more complex functionality with broadly the same interface specification. It also includes support for additional LTE features like LAA (Licensed Assisted Access) and NB-IoT.

The first version of the management plane spec provides an open multivendor M-plane model for radios based on standardized protocols like NETCONF/YANG. It includes a comprehensive YANG model developed for LTE and 5G radio.

The group said the new definitions should allow a wide range of vendors to develop innovative, best-of-breed RRUs and BBUs to support different deployment scenarios, while allowing easy integration with virtualized infrastructure and management systems using standardized data models. That would get away from the vendor lock-in enabled by non-uniform specs like CPRI, while also encouraging a wider variety of RRH types to support the growing number of use cases and deployment topologies envisaged for 5G.