Advances in Fronthaul: Where are we now?

We live in a connected world and everyone has at least one smartphone or smartwatch on which they connect to their Twitter or Facebook, Skype, FaceTime, Netflix accounts and other video bandwidth hungry applications on a daily basis. Everything is video, HD, everyone need high speed connection, thanks to high quality camera and everyone expects no lagging and clear deliveries from their service providers. They need it everywhere, at home, on the road, on vacation and all this on multiple devices. According to a Cisco study1, there are now 3.47 devices per person, which is expected to double within the next 5 years.

Customers have little patience for poor coverage. This is when churn comes in play and becomes the biggest challenge for mobile network operators (MNOs). In order to meet their service level agreements (SLAs), they need to provide:

• High-speed connections (LTE/LTE-A)
• Good and constant coverage
• Rapid service to their entire subscriber base

Evolution in the radio access network (RAN) technology and fronthaul networks aim at overcoming these challenges.

If we look at a typical cell site, we see that there are on average 1000 subscribers per cell, 300 to 350 subscribers per sectors and that too many users are simultaneously using the same capacity. On the following image, the yellow part showcases poor coverage, being out of proper reach from the two closest macro towers.

How can MNOs increase capacity and coverage? As depicted in the next illustration, they can do so by:

• maximizing sites by adding sectors to existing locations, e.g. adding twin sector antennas
• distributing antennas over a given territory (DAS), which can be outside or inside buildings

This is why today’s wireless network reality is composed of multiple network architectures, including Macrocells, Picocells, in-building DAS, Small Cells, and Carrier Wi-Fi, what we would call, Fronthaul.

All of these technologies need to be synchronized at all times and provide seamless coverage between them. Fronthaul networks have seen the most changes lately. New protocols and technologies, such as common public radio interface (CPRI) and open base station architecture initiative (OBSAI), are now transported over fiber instead of copper resulting in new deployment challenges.

So, where are we now?

Well, depending on region of the world, a lot of the migration to fiber in fiber-to-the-antenna (FTTA) network is taking place at the moment–switching copper connections between basestations to remote radio heads (RRUs) was the first step.  Within the next 2 to 3 years, fronthaul networks will be evolving to encompass multiple baseband units (BBUs) in one location controlling multiple cell towers, which is called BBU centralization or Centralized RAN (C-RAN), and which has already started in North America and Asia. Within 3 to 5 years, we’ll see investments in mobile equipment technology and the virtualization of multiple BBUs into one piece of equipment that will control multiple towers, which we call Cloud-RAN.

For more information on these technologies, watch our recent  Webinar Series on Fronthaul Testing.  This webinar series covers everything you need to know to efficiently qualify FTTA networks and confirm that RRH and CPRI links are fully functional before leaving the cell site–in just one field trip.  

_{1 Source: Cisco IBSG, April 2011}