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Network functions virtualization proponents have long touted disaggregation and virtualization benefits for wireless networks, including better agility, new applications and lower costs.
Wireless infrastructure incumbents -- such as Ericsson AB, Huawei Technologies Co. Ltd. and Nokia Corp. -- are primarily in charge of the ongoing 4G network buildout with traditional radio access network (RAN) architectures. Over the next five to seven years, the migration to 5G will offer operators new opportunities to explore virtual RAN (vRAN) deployments through standards consortia and smaller startup suppliers.
For the purposes of this article, the terms cloud and virtual RAN can be used interchangeably.
Defining the RAN and virtual RAN
RANs provide wireless connectivity between end devices -- e.g., smartphones, PCs or IoT devices -- and the core of a wireless network. RANs are implemented in network equipment form factors and typically consist of a base station -- including radios -- at the remote cell site and base station controllers.
The vRAN alters the traditional RAN architecture: It splits and centralizes control of wireless functions to optimize performance and cost. The three main components of cloud or virtual RAN architectures are:
- a centralized baseband unit (BBU) containing compute resources;
- remote radio units (RRU); and
- transport networks that connect multiple RRUs to the BBU, typically through fiber.
The benefits of a virtual RAN
Proponents of virtualized RANs promise a range of benefits, including improved performance, reduced Capex and lower latency. A vRAN uses network functions virtualization principles to provide different hosting abilities to virtualized applications on common hardware platforms. Other vRAN benefits include intelligent traffic steering between distributed cell sites, locally cached data to reduce latency and higher reliability.
In order to deliver its promised performance improvements, 5G architectures require more cell sites with different sizes than those in 4G architectures. These vRAN architectures are critical for the control and operation of new 5G base stations.
The virtualization of RAN functions requires low latency, high bandwidth connections between cell sites, and centralized or distributed control points -- which likely means using fiber optic networks. A plethora of competing standards organizations -- such as the O-RAN Alliance and the Telecom Infra Project -- are currently developing vRAN standards.
A RAN is a critical aspect of a mobile network, and integrating virtual elements from different suppliers is still especially challenging.
Supplier options for virtual RAN
Mobile operators have a number of vRAN suppliers to choose from, including incumbents such as Ericsson, Nokia, Huawei, Samsung and ZTE. Smaller suppliers include Altiostar Networks Inc., Asocs, Mavenir Systems Inc. and Saguna. Yet vRAN lacks depth and breadth in terms of its independent software vendor ecosystem -- only the largest suppliers have the resources to implement 5G vRAN.
Rakuten Inc., a Japanese e-commerce supplier of wireless deployments, is a poster child for disaggregated wireless networks, including vRAN architectures. Rakuten is currently building a greenfield network in Japan to compete with Japanese wireless operators -- including NTT, KDDI and SoftBank -- which will be operational in late 2019.
Other suppliers Rakuten is partnering with include Altiostar, Cisco, Fujitsu, Intel, Mavenir and Red Hat, among others. Rakuten plans to move its network to 5G in around 2020, depending on regulatory approval.
Recommendations for wireless operators
VRAN is in the early stages of development, with a number of leading mobile operators working on proofs of concept and with Rakuten in the middle of building its vRAN for 4G deployments.
A lack of standards and high variability for specific vRAN implementations by incumbent and startup suppliers may hinder near-term adoption. Early vRAN services will likely target greenfield deployments, like Rakuten's. The high speed communications required between the radio and compute elements -- RRU to BBU, for example -- will favor deployments in dense, fiber-rich geographies, like in large cities, such as Singapore.
Because 5G requires specialized radio technologies, it tends to favor suppliers with large R&D budgets. Multivendor vRAN deployments will be challenging due to the complexity of integration and the lack of mature standards.