ZenFiSo, what exactly is “fronthaul”? The short answer to that question is that fronthaul is essentially a fiber distribution network that provides connectivity between Remote Radio Heads (RRHs) in the field to the Base Band Units (BBUs) through a protocol known as Common Public Radio Interface (CPRI).  Neutral hosts are excited about this new network function because it provides connectivity to more locations; carriers are excited because it lowers CapEx on the base station; network operators are excited because it increases leased lines; and end-users are pumped because it enables more Shark Tank episodes while waiting for the bus.  

Why bother, you may ask? Cellular networks currently operate under constant pressure to provide greater throughput. With accelerating growth rates of smartphone usage, emerging Internet of Things (IoT) and their voracious appetite for bandwidth, denser networks are needed. So, how do you address the problems of required coverage and capacity along with interference management and spectral efficiency all without placing an even greater demand for expensive backhaul capacity?  Fronthaul.

Fronthaul networks help ameliorate (isn’t that a great word?) the shortcomings of small cell backhaul networks, and extend connectivity to enable greater data rates. Additionally, they help to relieve the pressure wireless operators face on their backhaul topology by providing a method to perform interference coordination and spectrum allocation at a central site through common clocking, while simultaneously eliminating the need to distribute synchronization information to each remote site. Not only this, but the fronthaul network also helps offload the demand for potentially expensive backhaul capacity. The high bandwidth of fiber is ideal for high data capacity AND low latency, along with the flexibility of adding wavelengths along a link, should those needs increase.

To really get a sense for the power of this type of architecture, if we separate the currently integrated RRH and BBU, placing the RRH where it’s needed and the BBU in a “hotel” situation, we can now take advantage of a few things in order to optimize our network.

  • RF signals generated at BBU co-located sites among pooled BBUs help achieve tight coordination of the timing signals necessary to allow the network to function.
  • Improved interference management (MIMO technology) and higher cell utilization is achieved.
  • SDN techniques orchestrate network elements across front- and backhaul to enable a highly programmatic network (faster time to market, changes, etc.).
  • A fiber based front-haul network, allows for the use of various wavelengths for secure isolation of signals (or as a wholesaler, different operators on the same core infrastructure).
  • Fiber, with its low attenuation, allows longer distances between BBU/RRH, thus allowing greater pooling and centralization of BBUs.

Okay, now that we have a deeper understanding, the next question is: why should we care? Wireless traffic is projected to have a compound annual growth rate over 60 percent over the next couple years, and that traffic requires advanced networks that rely on distributed capacity. Fronthaul fiber is a key connection in this ecosystem but it doesn’t come without a cost.

For content providers, having the RRH “closer” to consumers of that content reduces the inconvenience of delay or lag in getting what end-users want on their smartphone or tablet.   As a network provider, you can build your own fronthaul network and obtain all of the architectural and operational benefits previously outlined for yourself. Lease the fiber, install your RRHs and BBUs. This new type of coverage is a game-changer as networks get crowded and data demands grow.  As an MNO; maybe you want to share this cool infrastructure in a co-opetition sort of way. This method, through multiple wavelengths in your fronthaul fiber network and co-located pools of BBUs, possesses the ability to potentially lower your CapEx and OpEx – more so than going it solo.  If you are a Wholesaler, build this yourself with BBU colo facilities in the juiciest markets, and sell to the biggest players (or MVNO to utilize this architecture). Everyone wins!