xRAN Forum approves Fronthaul Interface Specification for NexGen Open RAN architecture

Executive Summary:

On April 12th, the xRAN Forum (xRAN.org) announced the public availability of the xRAN Fronthaul Specification Version 1.0 – the first specification made publicly available from xRAN since its launch in October 2016.  The specification was said to permit “a wide range of vendors to develop innovative, best-of-breed RRUs (remote radio unit) and BBUs (base band units) for a wide range of deployment scenarios, which can be easily integrated with virtualized infrastructure and management systems using standardized data models.”

Why is a new RAN architecture needed?

Current RAN architectures result in sub-optimal use of scarce spectrum and radio resources as well as make it hard for operators to program them quickly to meet emerging customer needs. Amid exploding demand for bandwidth and intense demands from new services, carriers need an alternative approach to address the escalating capital and operational costs of the existing design as well as make the network more agile to deploy new services.

Why It’s Important:

The new specification was said to “deliver on important operator member requirements.”  It defines open interfaces between the remote radio unit/head (RRU/RRH), the baseband unit (BBU) and the operation and management (OAM) interface to simplify interoperability between suppliers. It’s significant because traditionally, the RRU and BBU had to come from the same vendor.  By complying with this spec, different vendors (best of breed?) could provide each of those pieces of equipment.  The desired outcome is for a wireless network operator to buy an RRU from one vendor and a BBU from another vendor such that they’ll work together via a common interface.  Some say it’s going to bust up the old “cartel” of RRU/BBU suppliers.

The xRAN Fronthaul spec was said to address several key operator-defined requirements, including:

• BBU – RU interoperability based on well specified control, user and management plane interfaces.
• Efficient bandwidth scaling as a function of user throughput and spatial layers to address
increasing bandwidth needs and Massive MIMO deployments.
• Support for LTE, NR, associated features, 2T – 8T RU products and Massive MIMO beamforming
antenna systems.
• Advanced receivers and co-ordination functions.
• Ethernet based transport layer solutions.
• Extensible data models for management functions to simplify integration.

The xRAN Forum Front Haul Working Group is chaired by Verizon.  A spokeswoman for Verizon, told Lightreading in an email that the xRAN spec defines an “open Internet-based standard on which future RAN products will be built,” while ORAN is an effort to “ensure various proprietary CPRI-based systems can understand one another’s languages and operations.”

Note: CPRI (Common Public Radio Interface) defines the interface between Radio Equipment Controllers (REC) and Radio Equipment (RE) such that multiple vendors can provide different parts of a base station.

Selected Quotes:

“Our vision to develop, standardize and promote an open alternative to the traditionally closed, hardwarebased RAN architecture is becoming a reality,” said Dr. Sachin Katti, Professor at Stanford University and Director of the xRAN Forum. “Our operator members have been very focused and clear on requirements and our ecosystem of contributing members have risen to the challenge. The Fonthaul Specification is the first of several open interface specifications we expect to be released in 2018.”

“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, Vice President, Network Technology Development and Planning at Verizon. “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.”

“We are pleased to have worked with xRAN members in reaching the key milestone of delivering the first open xRAN fronthaul specification,” said Dr. Hiroshi Nakamura, EVP and CTO of NTT DOCOMO. “We believe that the completion and publication of this specification will contribute in further advancing the RAN and in expanding the ecosystem in the 5G era. DOCOMO will keep contributing to this activity with the experience we had in realizing multi-vendor interoperable RAN with our partners using common interfaces for our LTE network.”

“The xRAN Fronthaul Specification is a foundational component in the xRAN architectural vision and vital to accelerating the worldwide deployment of next-generation RAN infrastructure network operators demand,” said Alex Jinsung Choi, SVP Research & Technology Innovation, Deutsche Telekom. “Going forward, by connecting these specification activities to the broad architectural scope in ORAN, we can ensure the implementations across a wider community of suppliers to promote both innovation and open market competition.”

“xRAN’s release of this jointly-developed open specification creates the first wave of a positive sea change for our industry, transforming the way next-generation RAN infrastructure will be built, managed and optimized,” said Andre Fuetsch, CTO and President AT&T Labs. “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.”


tower cell

The specification is designed to allow for a range of vendors to develop best-of-breed RRUs and BBUs for various deployment scenarios. (Pixabay)

About xRAN Forum:

The xRAN Forum was formed to develop, standardize and promote an open alternative to the traditionally closed, hardware-based RAN architecture. xRAN fundamentally advances RAN architecture in three areas – decouples the RAN control plane from the user plane, builds a modular eNB software stack that operates on common-off-the-shelf (COTS) hardware and publishes open north- and south-bound interfaces to the industry.

xRAN Forum operator members include: AT&T, Verizon and Deutsche Telekom, KDDI, NTT DoCoMo, SK Telecom and Telstra.  The vendor and academic community is also represented in the xRAN Forum by AltioStar, Amdocs, Aricent, ASOCS, Blue Danube, Ciena, Cisco, CommScope, Fujitsu, Intel, Mavenir, NEC, Netsia, Nokia, Radisys, Samsung, Stanford University, Texas Instruments and University of Sydney.









5 thoughts on “xRAN Forum approves Fronthaul Interface Specification for NexGen Open RAN architecture

  1. Why is this spec work not done in ITU, IEEE, or other accredited standards organization?
    ITU-R Working Party 5D is responsible for the overall radio system aspects of the terrestrial component of IMT systems. IMT is comprised of IMT-2000, IMT-Advanced and now the under-development IMT-2020. IMT covers typical mobile broadband cellular systems currently in deployment and the future development of mobile systems including 5G, providing a range of service capabilities for the three main usage scenarios of mMTC, URLLC, and eMBB. These service capabilities may be provided over a set of schemes ranging from narrowband to broadband IMT-based technologies.

    Recommendation ITU-R M.2083 describes the framework and overall objectives of IMT systems for the year 2020 and beyond and describes IMT-2020’s envisaged usage scenarios covering applications such as smart cities, smart homes, m-health, m-education, connected cars, connected industrial automation, wearables, etc. These usage scenarios and applications are currently under development in various segments of industry, government, and academia, thereby providing for a very fast-paced growth. These services often raise stringent requirements on throughput, reliability, latency, mobility, the number of concurrently connected devices, and energy efficiency among others.


  2. These days we have pop-up alliances, consortiums, forums and the more structured Telecom infrastructure projects. While they all produce specifications, none of those organizations are official, accredited standards bodies.

  3. There is also an Open RAN Alliance that says they are taking over the xRAN Forum. What else is new?

    On Feb 27, 2018: AT&T, China Mobile, Deutsche Telekom, NTT DOCOMO, and Orange jointly announced the creation of the ORAN Alliance. The ORAN Alliance is a world-wide, carrier-led effort to drive new levels of openness in the radio access network of next generation wireless systems. ORAN will combine and extend the efforts of the C-RAN Alliance and the xRAN Forum into a single operator led effort.
    By combining and extending the objectives of the C-RAN Alliance and the xRAN Forum, the key principles of the ORAN Alliance include:

    Leading the industry towards open, interoperable interfaces, RAN virtualization, and big data enabled RAN intelligence.
    Maximizing the use of common-off-the-shelf hardware and merchant silicon and minimizing proprietary hardware.
    Specifying APIs and interfaces, driving standards to adopt them as appropriate, and exploring open source where appropriate.
    “ORAN represents a comprehensive embodiment of Communication 4.0 and is empowered by the true Information, Communications and Data Technology (ICDT) convergence,” said Zhengmao Li, CTO of China Mobile. “It will drive the radio access network from Green and Soft to Open and Smart. And ultimately operators will expect future networks to be built with deeply embedded intelligence, much higher efficiency, lower cost, great agility and flexibility, and all at manageable complexity.”

    “To take full advantage of the flexibility of 5G, we have to go beyond the new radios and change the overall architecture of the end-to-end system,” said Andre Fuetsch, President AT&T Labs and Chief Technology Officer. “Open modularity, intelligent software defined networks, and virtualization will be essential to deliver agile services to our customers. ORAN will accelerate industry progress in these areas.”

    “For 5G to unlock new business opportunities and markets, it is essential that we evolve a RAN infrastructure platform that allows us to innovate quickly to meet customer expectations. The ORAN approach, to drive more openness, modularity and programmability in our future networks, can enable a more agile delivery of services to our customers,” said Alex Jinsung Choi, SVP Research & Technology Innovation, Deutsche Telekom. “We are excited that the ORAN Alliance will build on and continue the journey we started in XRAN to extend the capabilities of RAN technologies and enable next generation open implementations.”

    “5G is expected to facilitate the creation of new vertical markets, the speed of which will be accelerated by the high flexibility and high intelligence derived from open APIs and interfaces,” said Dr. Hiroshi Nakamura, EVP and CTO of NTT DOCOMO. “We have experienced that openness can provide opportunities for expanding markets. We believe that ORAN will evolve open and cost effective radio access networks and that it will further advance them into the next stage.”

    “In order to respond to the growth of demanding business capabilities and affordable systems, 5G radio sub-networks need to evolve towards more flexible, open and smarter solutions,” said Emmanuel Lugagne, SVP Orange Labs Networks. “The work of the ORAN alliance will be a perfect driver for the industry to help achieve these promises.”

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