While people may debate what 5G will be, there are a few key facts that cannot be changed. These facts will shape what 5G will be. Based on this we expect that new winners will emerge who can capitalize on new trends through innovating new solutions. Therefore, aside from the hype that dominates 5G talk, the key is to peel the layers that shroud the fundamentals. Over the last three years of researching the potential for Cloud RAN (C-RAN), I saw all the traits of a disruptive technology lurking in the background (2014, 2015). But with 5G, I think this can all change, and C-RAN will bolt to the foreground in more than one way.
In looking at where technology is today, we note that it is getting ever more difficult to squeeze more capacity from spectrum. The spectral efficiency increase promised by 5G over 4G will be relatively small, perhaps no more than 20%. Instead the drive for more capacity and throughput will center on ‘multiplication’ of base stations and antennas. In other words, we are close to the Shannon limit and we can only get more capacity and throughput by deploying small cells.
Small cells as they are architected today present a major challenge when deployed in-band, at the same frequency as macrocells. The problem is that with more small cells, there is more ‘cell-edge’ where interference between layers will corrupt communications. Shifting small cells to another spectrum band helps, but also introduces other challenges related to mobility management. There are solutions to this in 4G, but 5G will feature much improved handling for hetnets as it will head to decouple the control from data plane and the downlink from the uplink. In such an architecture, it becomes necessary to anchor certain functions – or in other words – to centralize these functions. This is the first tenant of C-RAN.
The other issue related to deployment scenarios and use cases. There are far greater applications of wireless technologies today which in turn mandate a flexible architecture. Scalability becomes a key parameter that needs to be designed into wireless infrastructure solutions. This is where virtualization comes in as it will address scalability and provide a framework for deploying applications at the edge where they can be optimized for better performance including low latency and response time which is a key 5G requirement.
There is little doubt that Cloud RAN will feature highly in 5G as some functions are pulled away from the edge to improve performance. The question becomes which functions should be centralized and the hierarchy of the architecture. 4G provided a flat architecture that has proven to be problematic in optimizing performance of hetnets. 5G will reverse this trend to provide a flexible architectural framework where some functions are centralized even perhaps at multiple hierarchical levels while other remain at the radio. In doing so, will introduce another challenge: that of interfaces. This is something we have pointed to over two years ago in our white paper on 5G in January 2014 when planning for 5G first came on the scene. How will the leading vendors and larger ecosystem deal with this issue will be of great interest to watch unfold over the next few years.
Note: I am in process of updating my report on Cloud RAN and plan to release the third edition soon. If your company is involved in this space, I would be very interested to exchange market views with you (contact me here).