5G networks impact on fiber-optic cabling requirements and infrastructure

The early development of cellular networks leveraged macro towers using lower-wavelength spectrum capable of covering wide physical areas, positioning some up to 25 miles apart (if topology allowed). Towers, however, couldn't be placed everywhere, and small cells and radio heads were increasingly deployed to get the radio closer to the user. 

Small cells began to augment coverage and capacity in both 3G and 4G deployments, the term "densification" was introduced. With 5G, unlike its predecessors, a different set of frequencies will be used to implement new services. Sub-6-GHz will be used worldwide as the basis for city-wide mobile connectivity, while higher parts of the spectrum (millimeter wave frequencies of 24 GHz and above) will be used for high-bandwidth coverage. This new higher-band spectrum inherently has more significant distance coverage limitation. Thus, densification takes on an entirely new meaning. 

As the figure "Current 4G vs. future 5G networks" shows, the range of a typical 4G macro cell today can theoretically cover 10 square miles. The plans for 5G have as many as 60 small cells covering just one square mile. Actual deployment needs would vary, but a 1:600 ratio is a whole new level of densification to consider. 

Optical fiber is the preferred medium for existing wireless backhaul networks, and even in networks where this is not the case, the wireless backhaul eventually needs to connect into a fiber backhaul. Fiber will also be preferred for what is known as "fronthaul," connecting the dense mesh of 5G small cells. Why is this? Increased speeds with lower attenuation, immunity to electromagnetic interference, small size, and virtually unlimited bandwidth potential are among the many reasons why fiber is the right choice. The question becomes, "How many fibers are needed to support each cell?" And the answer will depend primarily on what technology protocols will be employed. 

Using our 60-cells-per-square-mile example, some estimates suggest the opportunities that will come from 5G depend heavily on real-time data, making lower latency and higher bandwidth more critical than ever. 8 miles of fiber cable would be needed to connect them. But wait, we need more information...

Today, many operators are using the Common Public Radio Interface (CPRI) protocol for radio heads on macro towers to support a wide variety of cellular services (2G, 3G and 4G/LTE). Traditionally, each sector and each band received a dedicated pair (one fiber each for transmitting and receiving data); operators could drop 24 or 36 fibers at a cell site and feel confident they had room to grow capacity at that location. 

Operators will need to decide on retaining point-to-point dedicated net-works and protocols or opting to employ wave division multiplexed (WDM) solutions to lower the fiber count needs. 

With a WDM solution, the same macro tower previously described could be serviced with only two fibers. There are tradeoffs with either method, and individual circumstances may lead to different decisions. 

With the densification of small cells growing (not only for future 5G needs but also for existing 3G and 4G needs), the proliferation of optical fiber and connection points along these networks will grow at a rapid rate. 

If an operator chooses to service a small cell site with one, two, or twelve fibers, how does it really impact the cost? One thing we know for sure in the deployment of networking infrastructure is that adding more physical capacity at the onset is far less expensive than coming back to add an overlay. The incremental increase in costs when the fiber count per cell increases isn't nearly as dramatic as you might expect. The cost increase to jump from one fiber to twelve fibers is under ten percent. 

Operators are trending toward a converged approach in the outside plant where wireless networks overlay with wired deployments. We've seen it in the metro for years, and now fiber-to-the-home builds are being merged with wireless densification initiatives. Driven by the cycle of consumer demand, new applications, and bolstered infrastructure, fiber demand continues to spiral upward. 

Taking 5G indoors

5G isn't just for the outdoors - its impact will be felt indoors as well. 5G will "break" a lot of distributed antenna system (DAS) networks, as the antenna placement will need to be closer than in 3G and 4G deployments.

Additionally, legacy copper-based infrastructures won't be able to keep up with 5G bandwidth. To keep up, smart buildings will undergo their own fiber-in-the-horizontal transformation.

Remember when you lost all signal as the elevator doors closed? With the majority of today's cellular traffic occurring indoors, many buildings have upgraded their cellular coverage so that those incidents are now few and far between. DAS and small cells have enhanced cellular in-building and large public venue coverage based on consumer demands for seamless connectivity. In fact, wireless is now often referred to in the industry as the fourth utility, as important to a building as water, electricity, or HVAC. This trend will only continue as the thirst for consumer connectivity continues. 

That's not all. We only briefly touched on the IoT, but imagine again sensors and devices on nearly all the "things" making them smart: utilities and lighting, refrigerators, trash cans, security systems, parking garages, etc. Add in wearables and augmented reality and you can begin to see the possibilities both indoors and out.

5G will most certainly be an evolution of today's networks, but the impact will likely be even more significant. Beyond being evolutionary, 5G is potentially revolutionary. The possibilities are virtually unlimited, but a smart, fiber-deep infrastructure will be paramount to making the vision real. 

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