Virtualized radio access network (vRAN) technology could be key to creating flexible, adaptable networks that help operators prepare for an unpredictable future. The rapid growth in mobile traffic volume and its increasingly dynamic nature, plus the many new types of user devices and applications, make it hard to predict demand. But vRAN can protect investments – and improve service -- all the way to 5G.
So what is vRAN?
A vRAN virtualizes network functions in the RAN using platforms based on general purpose processors, and takes a standards-based approach that follows the ETSI network functions virtualization (NFV) model. The aim is to make the RAN more open and flexible, and to optimize hosting of both new and existing functions. This enables the deployment of additional value-add mobile services at the network edge -- services that generate revenue for operators and deliver a better user experience.
To create a vRAN, the network architecture evolves to centralize, virtualize, and pool some previously distributed functions while some previously centralized functions move closer to the edge.
The functions of the base band unit (BBU) from the base station site are implemented using virtual machines (VMs) on generic servers at a central location. This creates optimal conditions for efficient scaling and pooling of resources and allows statistical dimensioning across multiple base station sites, be they macrocells, metrocells, or a mix of both.
The overall BBU capacity required is reduced, because the resources allocated to Layer 2 and Layer 3 parts of baseband processing, which are sensitive to user load, are scaled dynamically in response to the load.
Alcatel-Lucent uses the same approach to virtualize advanced control functions. Performance can be improved if they are neither distributed at the radio sites nor concentrated in a fully centralized location, but implemented at an intermediate level in the RAN. These control functions include enhanced scheduling and coordination and some virtualized self-organizing network (SON) functions to improve cell coordination and interference management.
Likewise, applications such as local breakout and video caching could be virtualized and implemented in a vRAN to optimize service performance.
vRANs create an adaptable and flexible network
While much of the commercial focus so far has been on using NFV in the core network and IMS, service providers stand to benefit from centralization and virtualization of the RAN, too. With a vRAN you can create a more efficient and adaptable network using load balancing. VMs can be added dynamically in seconds, and they can be released to another application just as quickly when no longer needed.
vRANs also reduce the total cost of ownership of the network. The smaller footprint of equipment at the cell site simplifies site acquisition and build, and lowers site lease costs. Applications running on VMs can easily be transferred from 1 to another with nearly no network disruption – simplifying maintenance and upgrades and thus reducing operational costs.
vRANs also allow operators to make better use of their RAN assets. They make it easier to share network resources among different market players, and to implement innovative “RAN-aware” services.
Adopting a convergent virtualized network function approach across both fixed and mobile access technologies means a more consistent service experience for the end-user and greater reach for application developers. Bridging between cloud and RAN allows the creation of cloud services that alter the end-user quality of experience, providing operators with new ways to address competitive challenges from over-the-top application providers.
Future-proofing the RAN for 5G
Deploying a vRAN is also a key step on the road to 5G. The need for open-loop, contention-based services to support the Internet of Things and the expected M2M traffic explosion will require smart control of network resources on a service-by-service basis. As will the requirement to integrate multiple access technologies in a single solution, especially in dense urban areas where access technologies could include Wi-Fi®, LTE, and new 5G and millimeter-wave radios.
With the BBU separated from the radios, new front-end units can be introduced more easily to match new radios. Moreover, if the BBU separation is done appropriately, then higher-order MIMO systems, as expected under 5G, will be possible at radio sites with no negative impact on transport – meaning less strain on the fronthaul (more detail on that in a future article!). vRAN will make it easier to deploy new features and algorithms that optimize resource usage and, again, deliver that high quality of experience to the end user.
With a vRAN, the hardware is almost independent of the applications, so operators can protect their investment through incremental upgrades of the hardware platform using the best available IT hardware at a given time. And by sharing the same platform between multiple hosted applications. By uncoupling network functions from the underlying hardware, and radio units from digital processing, vRAN will set up the flexible and dynamic RAN environment needed to help operators prepare for the introduction of 5G.
vRAN deployment is on the way
vRAN does not have to be implemented all at once geographically or functionally. Software deployed on VMs can replace dedicated devices as the network upgrade cycle permits. vRANs can even be deployed in areas where fiber to the base station site is not readily available, since Alcatel-Lucent has developed a dual-site BBU architecture that reduces the load on the transport infrastructure.
Alcatel-Lucent is working with China Mobile and Intel on a virtual BBU proof of concept. It was showcased at Mobile World Congress 2014, the recent SDN and Openflow World Congress in Dusseldorf, and a pre-commercial version is scheduled to be trialed in selected networks in 2015.
Also, our virtual radio network controller has been carrying traffic since last spring, the 1st commercial vRAN product running a RAN function ever implemented in a live network. In the future, Alcatel-Lucent will take vRAN further and virtualize more advanced features, building on the company’s strong experience and existing platforms.
vRAN is here, is proven, and is set to play a critical role in the future of mobile networks.
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