News that AT&T and Nokia are working together on a key element of the emerging Open RAN (ORAN) platform is a sign that momentum is growing behind the move to break down the proprietary network architectures of the past – to the extent that one of the vendors which made its fortune from closed networks now feels compelled to support the open approach. The two companies are jointly developing a RAN Intelligent Controller (RIC) for automatic optimization of the network. This will be open sourced within the broader ORAN platform and help to drive an interoperable ecosystem and a fully programmable mobile network. The deal follows only weeks after Nokia announced a similar collaboration with China Mobile.
The telecoms network has been one of the last bastions of proprietary technologies, remaining largely resistant to the open source waves that have been sweeping the data center and enterprise sectors for two decades. But the walls are tumbling down now, a trend that could rejuvenate traditional operators by transforming their costs and flexibility; or open the gates to new, more agile challengers. However it turns out for telcos, one of their number, AT&T, will have played a significant role in turning the network into an open environment, and by spearheading many of the key projects, it will hope to secure significant influence over next generation platofrms, as well as ensuring it emerges as one of the open source winners.
Several of AT&T’s initial developments, which it placed into open source, came almost entirely from its inhouse efforts. The ONAP (Open Network Automation Protocol), xRAN, Akraino and DANOS initiatives are all based on technology that originated with AT&T, covering a wide range of critical pieces in the modern network (management and automation or MANO, disaggregated RAN, edge compute and the virtualised network operating system, respectively). These developments are important to the US operator’s own ambitious efforts to rework its platforms and cost base around virtualisation, software-defined networking (SDN) and white box network hardware. They are also important to its efforts to shape the next generation network in a way that suits its business case, and enhances its industry influence.
As it accelerates these efforts, it cannot avoid working with large vendors. For all their challenges, they remain incumbent in all the world’s large telco networks and have the ability to bring new technologies to market quickly and with high impact. And while taking part in open source initiatives – whose aim is a commoditized, fully interoperable network with the intelligence in open software – is like turkeys voting for Christmas, the head of steam gathering behind the new-look platforms is making it hard for vendors to remain aloof. If they do so, they risk ceding control of next generation platforms to operators and tamer suppliers – whether start-ups like those being incubated by operators under the Facebook-led Telecom Infra Project (TIP), or large companies like Samsung which seek to bolster their infrastructure business.
Ericsson and Huawei, for now at least, remain resistant to the new approach, but Nokia has been the most open to a software-driven model since it launched its Liquid Net architecture in 2011 (when it was still NSN); and it has aligned itself with several of the open, and even open source, efforts, including TIP. It contributed code, as did Samsung, to the xRAN Forum, which went on to merge with the China-oriented Cloud-RAN Alliance to form the ORAN Alliance. This is heavily operator-driven – it was founded by AT&T, China Mobile, Deutsche Telekom, NTT Docomo and Orange, and they were later joined by Bharti Airtel, China Telecom, KT, Singtel, SK Telecom, Telefonica and Telstra. Nokia is listed as a contributing member.
In April last year, the first xRAN specifications were published, addressing the fronthaul link between the centralised and virtualised baseband unit (BBU), and the remote radio units (RRUs) in a disaggregated RAN architecture. Many operators believe such a RAN will bring new levels of resource flexibility, saving operating costs and improving quality of service for users, but a major barrier has been the lack of a common interface so that different BBUs and RRUs could be mixed and matched. This is clearly essential to avoid another generation of vendor lock-in, and to introduce price competition to help operators reach their cost reduction targets.
Those initial xRAN specs will feed into the combined ORAN platform, and now the ORAN Alliance is working on the first technology under its new brand, with AT&T and Nokia taking the lead.
The two companies are jointly developing an open source RAN Intelligent Controller (RIC) which will align with the broader ORAN platform as that evolves. The RIC will incorporate a set of functions and interfaces that support advanced RAN optimization through policy-driven, closed-loop automation. The software will allow services to be deployed more quickly and flexibly because it will make the RAN more programmable. Most importantly, the RIC will be one enabler of the operators’ dearest dream, an open
multivendor ecosystem of interoperable RAN elements.
It will achieve this by taking a very modular approach, harnessing key tools from the open virtualised network community. So the RIC will take the form of an extensible real time microservices framework, in which interoperable components and virtual functions, such as the radio information database and open control plane interfaces, can be combined as required. These will support use cases such as mobility management, management, load balancing, radio resource control and RAN slicing.
The platform will also support interfaces to third party applications to add more mobility functions such as cross-layer optimization and machine learning.
“We’re delighted to work with Nokia on co-creating an open source implementation of the RIC platform to accelerate innovations and interoperability in the RAN,” said Mazin Gilbert, VP of advanced technology and systems at AT&T Labs. “We continue to look for opportunities to drive open platforms and open interfaces in the community.”
“Nokia is a strong proponent of RAN network openness and has been active in numerous open source communities, contributing code and defining open interface specifications,” said Mike Murphy, Nokia’s north America CTO, in a statement.
The impact of the RIC will not be confined to ORAN – Nokia and AT&T will also use it to enable new capabilities in the Akraino Edge Stack, another AT&T-initiated effort now hosted by the Linux Foundation. Akraino’s main aim is to create blueprints for open source edge compute and edge cloud infrastructures and applications, in order to accelerate development of an open ecosystem which can address many vertical industries’ edge requirements. AT&T said it has signed a multiyear agreement with Nokia to expand Akraino Edge Stack functionality by supporting the RIC.
This is Nokia’s second open network collaboration with a major operator in the space of a few weeks. Last month, it announced a similar alliance with China Mobile to develop open RAN interfaces, with a focus on practical use cases. It will work with the China Mobile Research Institute (CMRI) to work on key aspects of an open, interoperable and multivendor RAN, including:
- 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.
On the ORAN front, the Alliance scored a major point at the end of last year when it announced that Verizon had signed up, despite the heavy influence of its arch-rival AT&T. At the same time, the group demonstrated the scale of its ambition by launching a new collaboration with The Linux Foundation, which hosts it, to establish a broad open source community dedicated to RAN software. And it released its first white paper, ‘ORAN: Towards an Open and Smart RAN’.
Verizon may not have been a full member before, but it had been part of the xRAN predecessor, chairing a fronthaul working group. It contributed to April’s xRAN Fronthaul Specification Version 1.0, as did two of its 5G suppliers, Nokia and Samsung. There may have been crossover with Verizon’s pre-standard 5G implementation, which also features a hefty measure of virtualization and network disaggregation.
“The release of the xRAN Fronthaul Specification is a groundbreaking advancement toward enabling an open RAN architecture to support next generation products and services,” said Bill Stone, VP of network technology development and planning at Verizon, last month. “xRAN compliant radios coupled with virtualized basebands provide much needed flexibility to support rapid development and deployment of RAN products. By adopting xRAN specifications, we will be able to speed innovation, increase collaboration and be more agile to a quickly evolving market.”
Andre Fuetsch, CTO and president of AT&T Labs, added: “Equipment that supports open specifications from xRAN (and ORAN in the future), combined with increasing RAN virtualization and data-driven intelligence, will allow carriers to reduce complexity, innovate more quickly and significantly reduce deployment and operational costs.”
Antenna vendor CommScope has already announced a 5G radio/antenna solution based on the xRAN interface specifications, which takes instructions from a virtualized baseband and integrates a beamforming active antenna array operating in the 28 GHz millimeter wave band. Initially, it is targeted at fixed wireless access (FWA).
The fact that xRAN’s first specification was for fronthaul shows how vital this is to the vRAN business case, and to a new way of enhancing 4G and adding 5G. The reliance on the semi-proprietary CPRI protocol, and on very expensive fiber – capable of supporting the capacity and low latency required for a vRAN – have been the main obstacles to the new RAN. These barriers to implementing long-haul fronthaul links have meant that most early C-RANs have been very localized – consisting of a small number of macro layer radio heads, or a small cell C-RAN with an on-premise or cloud-based controller.