How to upgrade RAN in the face of fiber network constraints
The urgent fiber network challenge
The deployment of 5G will place a high demand on existing fiber routes many of which may not have been designed for the requirements we now anticipate. In major metro areas, 5G cell sites will be both denser in number, and denser in fibers per site – The Small Cell Forum estimates up to 350 small cells per square kilometer in dense urban areas  with fiber counts driven by new radios and new bands for both 4G LTE and 5G.
These new requirements may overwhelm existing metro fiber assets that were designed primarily for enterprise customers. The bottom line is that in many areas, there simply isn't enough fiber 'in the ground' to support multiple operators' plans for LTE Advanced and 5G.
Addressing this problem by laying more fiber will have a tremendous cost and time to market impact for 5G rollout. Complicating this challenge is the fact that many of the impacted sites are located on streetlights and utility poles where deploying extra equipment is difficult or impossible due to permitting constraints.
If these constraints are not a concern today, there is no question that they will soon become urgent as RAN planners advance deployments of capacity enhancements like carrier aggregation, and new bands like LAA and CBRS, not to mention 5G.
Finding an efficient solution
So what is the solution? Traditional Dense Wave Division Multiplexing (DWDM) can postpone or even avoid additional fiber investment by transporting many radio links on each fiber – making each fiber much more efficient. However, since many of these sites will be located on utility poles and streetlights, bulky DWDM equipment poses deployment challenges. Many existing DWDM solutions were not designed for outdoor use, do not support a range of different port counts, or just can't be installed easily on a pole due to size or configuration. What is needed is DWDM purpose built for these kinds of deployment scenarios.
Fronthaul purpose built for densification
Ericsson has been developing solutions to this challenge, well aligned to the small cell deployment scenarios common in dense urban metros, including utility poles. The Fronthaul 6000 DWDM portfolio will enable transport planners to overcome fiber network exhaust before it impacts LTE Advanced and 5G deployment timelines, while avoiding major new fiber investment.
Ericsson fronthaul (both active and passive) has a very small footprint, a variety of filter types and sizes and is hardened for outdoor use. The solution can support 24 radios on a single strand of fiber, and it has the highest port density in the industry. A range of concealment options are available to reduce permitting delays and simplify installation. Ericsson DWDM SFPs are optimized for use in 5G radios, and in harsh outdoor environments, to ensure the best end to end performance.
If you are concerned that fiber constraints will impact your LTE Advanced and 5G deployment timelines, Ericsson solutions are available today and are in service across the US market. Click here for more information.
4G small cell on utility pole
5G Small Cells
5G radios will be placed on utility poles close to the end user. They provide much higher bandwidth and are deployed more densely (100 to 350 per square km), which increases the demand for fiber.
 - Small cell forum