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.