Bringing Fiber to the Antenna – What’s Your Strategy?

Wireless network installers became very familiar with coaxial cable over the last 20 years, when it served as the primary transmission line system between the bottom and top of cell towers. Today’s wireless world is increasingly based on fiber and power cabling, however. Brendan Millard asks some good questions about how this major cabling transition might impact your future network.

Network installers

The dramatic shift to remote radio units (RRU) with third and fourth generation wireless technologies has created a real disconnect from the past when it comes to connectivity on cellular sites. First and second generation wireless technologies were mostly installed using traditional site architecture with the radio housed in a shelter or cabinet at the base of a tower, connected to the antenna at the tower top via coaxial cable. This architecture was a well established and understood practice. The interfaces were standardized, the cable sizes were well defined in relation to the tower height and installation practices had evolved over many years to become common practice.

Today, the interconnection between the bottom of the tower and the top is a brave new world for those that have been installing cellular systems for the past 20 years. Decreasing in deployment numbers is the coaxial feeder cable with which we are all so familiar. The installer today often is installing power cables and optical fiber cables between the baseband equipment at the bottom of the tower and the radio at the top. But which fiber cable? What size power cable? Terminated on site or pre-terminated? It seems every radio manufacturer has its own specification on what fiber cable and what conductor sizes should be used, what interfaces will be used and how it all should be done. Every wireless operator has its own preferences as well.

Radios have migrated to the top of the tower in part to improve the efficiency of power consumption on site. Power is no longer wasted on air-conditioning in equipment shelters or lost in coaxial feeder cables. The flipside is that radios are no longer easily accessible for maintenance and repair. As such, a lot of effort has gone into making RRUs as reliable as possible to avoid the complication of replacing them if they fail.

If an operator has gone to the expense and effort of putting high reliability radios on top of the tower, the last thing they want to do is use an unreliable or vulnerable solution to connect to them. Thus, although the simplest way to make the interconnection is to use separate fiber and power cables, an operator concerned about reliability of the network will insist upon the vulnerable fiber and power cables being housed within a conduit to protect them from damage from rodents, birds and even stray installers' boots.

With the growing demand for more data, more bandwidth and more services, many operators are installing multiple RRUs on their towers to cover multiple frequencies and technologies. In addition, they can already see the need to add further RRUs in the future as more spectrum becomes available to them. It can be a costly exercise to add new cables to a tower and may require the hire of expensive installation equipment such as a cherry picker. If a trunk fiber and power cable that can cover both today's needs as well as future requirements can be installed now, it will save operators on expense and problems when they add their future services.

Imagine a trunk cable that has sufficient conductors and fibers to handle the requirements of both today and tomorrow? What if that same cable could was armored to protect against rodents, birds and installation mishaps? And, finally, what if that cable could accommodate a range of manufacturers' current RRUs as well as changes to new and different RRUs in the future?

Wouldn't that interconnection solution be something worth investing in?

Have you thought about your overall RRU deployment strategy for today and tomorrow and how you can proceed with network modernization most effectively?