NFV at the wireless edge: Cloud RAN opportunities and challenges

Defining cloud RAN

The radio access network (RAN) provides the wireless connectivity between the end device (e.g., smartphone, PC or IoT sensor) and the core of the wireless network. Implemented in network equipment form factors, the RAN typically consists of a base station -- including radios -- at the remote cell site and base station controllers.

Cloud RAN (cRAN) significantly changes the traditional RAN architecture by splitting and centralizing control of wireless functions to optimize performance and cost. Leveraging the benefits of commercial processors (e.g., commercial off-the-shelf, or COTS, servers), compute-intensive processing can be centralized and efficiently pooled to handle changes in traffic flows.

Cloud RAN benefits

Proponents of cRAN promise a wide range of benefits, including better performance, lower latency for critical applications, lower Capex and simplified operations.

Proponents of cRAN promise a wide range of benefits, including better performance, lower latency for critical applications, lower Capex and simplified operations (lower Opex). Cloud RAN leverages NFV principles by providing the ability to host different virtualized functions/applications on a common hardware platform. Early trials have shown significant Opex benefits by reducing the space and power required at remote cell sites.

Additional benefits of cRAN include:

• Improved scaling and load balancing with centralized resources
• Better performance with intelligent traffic-steering between cell sites
• Fast access to locally cached data for low-latency applications
• Higher reliability by lowering the cost of redundancy

Challenges to cloud RAN implementation

Virtualization of the RAN is more challenging to implement than some early NFV implementations, such as virtual evolved packet core, virtual IP Multimedia Subsystem, virtual customer premise equipment, etc. Centralization of RAN functions will require low-latency, high-bandwidth connections between the cell site and a centralized control point. The wireless edge has been dominated by integrated offerings from the dominant telecom suppliers, including Ericsson, Huawei and Nokia. Currently, there are limited standards with regard to how the various functions of the RAN should be virtualized. There is general agreement that RAN virtualization will be a common aspect of 5G network implementations, but 5G is in the early planning stages and is unlikely to see broad adoption until 2020 (or later).

Cloud RAN options

Every supplier has a different architecture for its unique roadmap to cRAN implementation. For example, NEC and Intel Corporation are jointly developing a cloud radio access network that can virtualize some of the functions of mobile base stations and run them centrally on Intel-based servers.

Mobile operators have a number of cRAN suppliers to select from, including incumbents such as: Ericsson, Huawei, Nokia (and Alcatel-Lucent) and NEC. And, smaller suppliers with innovative cRAN solutions, such as: Altiostar, ASCO, Saguna and Parallel Wireless.

Recommendations for providers

Cloud RAN leverages NFV concepts to improve performance and traffic handling, cutting operational costs at cell sites, and potentially reducing Capex by employing COTS servers for many RAN processing functions. Cloud RAN is in its early stages of development, with a number of leading mobile operators working on proof-of-concepts, including China Mobile.

Lack of standards and the high variability of specific cRAN implementations by incumbent and startup suppliers will hinder near-term adoption. Early cRAN solutions are likely to target specific high-traffic areas (e.g., sport stadiums and convention centers). Broader cRAN implementation will occur over the next two to four years, as operators migrate toward 5G and incorporate NFV concepts -- including standardized servers, service chaining and dynamic traffic capacity.