The radio access network (RAN) is the critical asset that underpins the world's largest technology platform -- mobile communications. It is fundamental to wide-area connectivity and supports an enormous, and expanding, range of services.
Cloud RAN -- sometimes also known as software-defined RAN (SD-RAN) -- is emerging as central to the new wireless network architecture. As they "cloudify" their networks, operators are seeking to apply principles of centralized control and distributed processing to wireless access. This, inevitably, means a more software-centric, software-configurable RAN is emerging.
In the next-generation Cloud RAN architecture, real-time functions are deployed close to the user (e.g., at the antenna site) to accurately and efficiently manage air interface resources, while non-real-time control functions are hosted centrally (e.g. at a distributed data center) to coordinate transmissions across the coverage area. In 5G this architecture is being formalized with the Central Unit (CU) and Distributed Unit (DU) functional split.
Some of the key characteristics of the next-generation radio access network, include:
- Spectrum cloudification: In practice, the RAN may need to support multiple generations of radio interface on a common deployment to enable operators to migrate subscribers and refarm spectrum for new radio access technologies. The concept of "spectrum cloudification," where different RATs (radio access technologies) share the band dynamically in time, is therefore an important part of the Cloud RAN feature set.
- System efficiency: Coordinated radio resource management can be used to optimize transmit power and, in turn, network capacity and coverage. Different generations of radio technology can "share" transmit power in the same physical radio unit (DU) to improve spectrum utilization.
- User-centric performance: By scheduling transmissions centrally (in the CU), Cloud RAN can improve cell edge performance by reducing inter-cell interference and optimize end-user performance. This is driving the concept of the user-centric or "no-cell" RAN to ensure consistently good experience in high-density scenarios.
- Deployment and operational flexibility: Cloud RAN with coordinated scheduling can radically improve deployment flexibility by automating cell planning. This is important for ongoing operations in dense deployments or where operators need rapid on-demand capacity upgrades.
Important aspects of the new Cloud RAN architecture remain under development. The specific functions of the CU and DU are likely to vary based on the deployment and radio interface and this determines the requirements on the fronthaul transport interface and, in turn, the physical deployment model. In advanced 4G and 5G networks, the growing importance of massive MIMO adds another layer of complexity to the "RAN split" decision. Nevertheless, despite the development and deployment challenges, Cloud RAN capabilities will be increasingly important in cloud-centric mobile networks.
On April 25, Light Reading is hosting a webinar on CloudRAN & the Future-Oriented Mobile Network Architecture. To learn more about this topic, and to register (it's free!), click here.
— Gabriel Brown, Principal Analyst, Heavy Reading
This blog is sponsored by Huawei.