The challenges facing small cell deployment

Article By : Rajakrishnan Radjassamy

Small cell deployments will play a critical role in extending 5G’s reach and availability. However, as CSPs pursue their next-generation mobile networks, new technologies and use cases will present new challenges.

The transition from 4G to 5G mobile networks is well underway, but this generational shift is proving to be more labor-intensive than its predecessors. As communications service providers (CSPs) pursue the next-generation speed and applications 5G has promised to consumers and industries alike, the macro towers that formed the backbone of 3G and 4G networks are not enough to provide widespread coverage in 5G’s highest frequency bands. In addition, existing power solutions are unlikely to suffice for such power-hungry radios.

The Small Cell Shift

Originally developed to support the transition from 3G to 4G in densely populated areas, small cell deployments will play a critical role in bolstering 5G’s reach and availability. The challenge, though, is that the radios needed to facilitate “true” 5G—with high-bandwidth, millimeter-wave (mmWave) frequencies—can only cover about one mile (Figure 1). Utilizing more cost-effective and less obtrusive alternatives to macro towers will likely prove advantageous for CSPs and communities alike.

Figure 1 The 5G connected city will need densely packed small cells to support the traffic loads of congested cities.

However, getting there will be easier said than done. The small cell landscape will need to evolve rapidly to facilitate this endeavor. Not only will hundreds of thousands of small cell radios need to be manufactured and installed quickly, but power specialists will be tasked with developing forward-thinking solutions to power radios as cellular density needs arise. Succeeding in this endeavor will require strong partnerships between power conversion specialists, mobile network engineers, and CSPs. These groups will need to work together to develop forward-thinking solutions that can support the build out of 5G networks while addressing potential hurdles including shrinking coverage radiuses, limited footprints, rising power demands, and safety concerns.

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The control conundrum

The networks of macro cell towers that support 3G and 4G coverage across the country were built to overlap at their perimeters, with the assumption that the radios affixed to them would have coverage radiuses of approximately 10 miles. However, at 5G’s highest frequencies (currently the 24-megahertz band), a radio’s coverage area is expected to be less than 1 mile, leaving significant gaps between existing towers. Carriers will need to fill these gaps to achieve true 5G coverage.

Rather than having one tower covering a large radius evenly, small cells can be deployed with reasonable precision to offer reliable coverage in the places people live and work, while avoiding other areas like lakes, forests, or swamps where limited or no coverage is necessary. The ability to tightly control where small cell radios are deployed and the frequencies on which they operate will offer more efficient coverage in areas with diverse landscapes.

While better control and increased efficiency are both desirable outcomes, there can be challenges to achieving both. Each region’s deployments will need to be fine-tuned to its specific needs based on population density, topography, available carriers, and a variety of other factors. In addition, the number of radios needed at each site, the frequency bands they support, and the carriers operating them can vary—sometimes even within individual neighborhoods.

Small but mighty (complicated)

This may be stating the obvious, but it’s worth noting just how compact small cells really are. Small cell infrastructure is designed to be mounted on existing street furniture in populated areas, barely noticed by residents. A single 30- to 50-foot pole would have to accommodate a small cell antenna, a remote radio head, the necessary power infrastructure, a metering unit, an isolation breaker, and more. If multiple sectors need coverage, the number of antenna and radio heads needed increases accordingly.

Weight is also of concern. While some small cell equipment can be located at the base of streetlamps and poles, it’s often mounted high off the ground on the actual street furniture (Figure 2). If the equipment is too heavy, it can pose safety concerns and lead to infrastructure damage. As such, the equipment, and the enclosures themselves must be as lightweight as possible while still being durable enough to handle the elements. Finding cost-effective ways to ensure that small cells stay small, light, intact, and deliver reliable power and signals will be no simple feat.

Figure 2 Small cells are often mounted at the top of a streetlights posing both size and weight constraints for these 5G installations.

Power possibilities

Once a map that provides the right kinds of coverage is developed, radio frequency (RF) engineers and power specialists will need to determine the power demands of each individual cell, those nearby it, and for the network as a whole. This will allow them to develop solutions that can meet the diverse needs of the network and continue grow alongside it.

Since each small cell radio covers a much smaller radius than its macro cell counterparts, the radios will be able to operate on much higher frequency bands—and that requires more power. Throw in the sheer number of small cell deployments needed to cover an area and the rising cost of energy, the task of maximizing energy usage while reducing CapEx spend can become challenging for engineers.

The majority of small cell equipment has been designed to tap energy from existing fixtures—like streetlamps or traffic lights—to power radios, eliminating the need for extra architecture. This method helps keeps footprints small, but it comes with strings attached. The companies that own the poles, powerlines, and other street furniture could influence the choice of small cell architecture and deployment speed based on regulatory and city approvals.

CSPs are also considering constructing AC-to-DC conversion plants in areas where the available power supply can’t support the small cell equipment the area needs. Of course, this comes with an additional price tag of trenching the power cable if one does not exist already.

A Classic Quandary

The technology underlying 5G mobile networks has incredible promise. When fully realized, it will transform the way people live and work, bringing use cases that once seemed impossible within reach. However, that potential is contingent upon innovative solutions and creative problem-solving that are still on the horizon.

Fortunately, the challenge the industry and its power partners now face is not new. At its core, the power obstacle 5G deployments will need to overcome is the oldest in the book: how do we fit more power into smaller spaces and do it in a way that’s cost-effective, efficient, and safe?

Industry leaders and power solutions providers are taking steps to overcome these challenges by developing carrier-agnostic technology, more efficient radios, and purpose-built power solutions, while the ongoing expansion of the deployment will naturally see safety-related concerns diminish as people become more comfortable with the technology. With each passing day, offering true 5G coverage is getting closer as innovation leads the industry toward all the promised benefits of next-generation mobile networks.


This article was originally published on EDN.

Rajakrishnan Radjassamy is the director of the 5G and wireless segment for ABB Power Conversion.


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