Tower-mounted Amplifiers’ Expanded Role in the 5G Network: Part 1

In the first part of our two-part TMA series, we highlight issues the MNOs and their TMA partners face as they adapt to new challenges in a 5G-enabled world.

Tower-mounted Amplifiers’ Expanded Role in the 5G Network: Part 1

At the end of 2021, the monthly global average data usage per smartphone was about 11.4GB. Over the next five years, data volume is expected to nearly quadruple, hitting 41GB by the end of 2027. Thanks in large part to the new capabilities of 5G (which is expected to carry about 62% of all mobile traffic by 2027), mobile network operators (MNOs) are scrambling to fast-track their 5G roll-outs, making sure they can support the increased demands at the macro site-level. Admittedly, this information comes as no surprise to anyone in mobile network design; but it is a sobering reminder of just how fast the rules (and stakes) of the game are changing.  

In response to these tougher demands, network operators are employing a variety of technologies such as spectrum overlays, sector splitting and active antenna beamforming. At the same time, they’re deploying more multiband radios and antennas, multi-MIMO (mMIMO) configurations and other RF equipment. The net effects are more complex and overcrowded deployments, overloaded towers and a greater imbalance between uplink and downlink channels. It’s this last issue that provides the biggest threat to spectral efficiency, quality of service and, ultimately, operator revenues.


Link imbalance returns with a vengeance

Until recently, link imbalance and its effects on system performance have flown below the radar. One reason is because operators’ major focus was on capacity and coverage improvements. Another reason was that the downlink and uplink signals were imbalanced by design. Prior to 5G, air interface technologies limited the resources allocated to serving uplink traffic. That meant operators could steer more power to supporting their heavily loaded downlink signals without sacrificing too much uplink performance.

With 5G, the uplink and downlink capacity and capabilities are more balanced, in theory, but the practical reality tells another story. Given the huge increase in data demand and overcrowding in the RF environment, keeping the uplink and downlink signals in balance in today’s 5G NR deployments is becoming more difficult. Ironically, a key to addressing this growing issue is a technology that goes back more than two decades -the tower-mounted amplifier (TMA).

TMAs looking back and looking forward

For over 20 years, tower-mounted amplifiers (TMAs) have been used to compensate signal losses in the uplink. Prior to relocating the non-processing components of the radio to the top of the tower in the form of remote radio units (RRUs), operators connected the base station radio at the bottom of the tower directly to the antennas at the top. The long coax runs were notorious for signal loss. TMAs were installed in between the radio and antenna to compensate for the feeder loss. By boosting the signal level, the TMA improves the overall signal-interference-to-noise ratio (SINR) of the system. This reduces the noise figure of the base station receive path, improves the uplink budget and brings the downlink and uplink into balance. The result is improved overall cell coverage, efficiency and performance.

The efficacies of TMAs are not lost on today’s 5G mobile operators. According to a recent study from Future Market Insights, the global market for TMAs is poised to experience sustained growth over the next five years, increasing from US$5.43 billion  in 2022 to US$8.54 billion by 2027, with compounded annual growth rate of 7.8%. Not surprisingly, multi-band TMAs are projected to account for the majority of the business.

More vendors, more choices, more freedom

But if TMAs are to adequately address operators’ current challenges, they must satisfy a whole new set of requirements that didn’t exist 20 years ago. 20 years ago, there were far fewer RAN OEMs than exist today and MNO relationships were tied much more closely to their OEM partners. While the familiarity between the operator and their vendor ensured a level of efficiency, it also limited TMA selection based on what the vendor could provide. Today, thanks in large part to the trend toward open RAN design, MNOs exercise far more flexibility and control in designing and specifying network components. On one hand, this freedom enables operators to ensure a best fit solution. On the other hand, the typical RF path involves multiple equipment vendors; ensuring interoperability among equipment is a primary concern.

Growing application diversity

The roll-out of 5G NR has introduced additional RF frequencies as well as more complex multi-band configurations. This is forcing TMA providers to adapt their designs for each application. While frequency performance can be “dialed-in” with customization, multi-band capabilities must be engineered from the start. Dual-band and tri-band deployments are quickly becoming the norm, and demand for quad-band and penta-band solutions on the rise.

Space and weight constraints

More frequencies mean more equipment on towers that are already overloaded. There is growing demand for RAN equipment that makes the best possible use of available loads and space. TMAs are no different. Customization enables engineers to adapt the TMA’s design for the specific frequencies, reducing the size of the final product in the process. In many cases, engineers can also integrate other components, like combiners and filters, enabling MNOs to further consolidate equipment on the tower. The challenge is that most TMA providers are not equipped to provide this level of customization quickly enough to meet the operator’s aggressive roll-out schedules.   

Noisier RF path, tougher environment

As the RF environment at today’s cell sites becomes more complex and crowded, the need for higher performing TMAs is implicit. The noise level, especially from adjacent cells, poses a greater threat to signal quality, particularly at the cell edge. As mentioned earlier, KPIs—uplink/downlink balance, dropped connections, improved coverage and decreased transmit power—have serious implication on the balance sheet. The longer the solution can meet those KPIs, the stronger the MNO’s bottom line. However, environmental factors like more extreme weather patterns, air pollution, and even vibrations from low-flying aircraft can accelerate TMA wear and aging. The results are more frequent truck rolls and replacements. How well TMAs perform under these circumstances, and for how long, help determine the overall success of the site.

Stay tuned for part 2

These are just some of the more pressing issues that MNOs and their TMA partners face as they adapt to the new challenges of a 5G-enabled world. The wish list of TMA features and capabilities is ambitious but achievable. We cover that topic in part two our TMA blog series. Meantime, if you want to read more about CommScope's pioneering work in TMA development, I invite you to check out our numbers in our infographic.