Now that carriers have purchased C-band spectrum, these new frequencies will drive the build-out of 5G networks. Macro sites will be the best location for C-band radios and antennas, being already sited and built. Unfortunately, this will not be nearly as easy as one may think.
Why is the C-band so exciting for the expansion of 5G services and coverage? Although it is not the part of the 5G spectrum that promises to deliver the highest data communication rates, C-band will help wireless telecommunication carriers to achieve the optimal balance between speed and geographical coverage, allowing them to offer data rates as fast as 1Gbps over distances as great as several miles — the best combination for serving densely populated metropolitan and urban areas (see Figure 1).
This explains why Forbes magazine states that “the future of 5G in the United States (as it is in other countries) is in mid-band1” and why carriers have collectively spent over $80 billion to gain access to the first block of the C-band frequency spectrum (3.7-3.98GHz) which was recently auctioned off by the Federal Communications Commission (FCC) on behalf of the U.S. government. The first 100MHz (A-block) will become available for use late in 2021 with the remaining two blocks of 80 and 100MHz becoming available over the next two years. Having invested such large sums, carriers are now understandably eager to quickly deploy the new 5G radios and supporting infrastructure required to capitalize on their newly acquired bandwidth.
The nature of the demand for 5G services is evolving alongside the introduction of C-band frequencies. 5G is becoming the platform for a wide range of industrial and mission-critical business applications built on the internet of things (IoT) as well as real-time consumer applications such as gaming and autonomous driving. These applications are highly sensitive to any interruption in connectivity or responsiveness. It’s not all about bandwidth anymore: According to Forbes magazine, as C-band rolls out, “operators will be pressing to demonstrate they not only have the lowest latency network but provide the best network quality and jitter characteristics2”.
C-band signal quality and reliability need to be as high as possible for 5G to meet its potential.
Seeking an efficient rollout of C-band services, carriers are looking to locate new 5G radios within the macro cell sites that they use to provide existing services, such as 3G and 4G LTE. Most of these are located on towers and the rooftops of buildings that were chosen because they provide a desired level of signal coverage. Apart from being already well served by electrical and wired communications facilities, reusing them to support the rollout of C-band would also remove the inevitable costs and delays associated with applying to local government authorities for permission to locate cells at new locations.
The catch is that simply adding C-band radios to existing macro cells is not as straightforward as it may seem.
There are some obvious considerations, of course. The new radios and support equipment will take up more room and add weight to the structure. They will require more power — in fact, with their high bandwidth, 5G radios require more power than earlier generations, even though the power used per byte is much lower.
A challenging aspect concerns concealment materials used to hide radios and antennas (see Figure 1) and blend the macro site into the local architecture. With earlier generations of wireless service operating at frequencies below 1 GHz, most available concealment materials did not degrade the signals. Carriers could focus instead on matching the surrounding structure in terms of format, finish and color.
C-band signals operating at GHz frequencies, on the other hand, can be affected by the commodity fiberglass panels that have been routinely used across the industry to conceal macro sites.
Extensive testing by Raycap has shown that the insertion loss caused by fiberglass FRP and molded fiberglass on C-band transmissions far exceeds the 0.5dB limit (see Photo 1) that most carrier engineers consider reasonable. This is because C-band signals have smaller wavelengths that make them more susceptible to interference than sub-GHz signals. With losses as large as 2.5 dB, molded fiberglass, in particular, has significant potential to affect C-band signals and increase the likelihood of latency and jitter issues.
Raycap turned the tests on its own Stealthskin (SSV, ESSV) range of concealment products that have been used for years by the company in macro site concealments including towers, screen walls and side-mounted boxes. Over the C-band frequency range, these materials performed extremely well, exhibiting an insertion loss of less than 0.5 dB. For a wide range of C-band retrofits, Raycap can create custom shapes, textures and can paint rigid panels based on these materials to closely match existing architectures for aesthetic purposes.
Carriers looking even farther ahead to the future deployment of mmWave 5G, which offers even higher speeds over shorter distances, may also consider Raycap’s InvisiWave material, which, during our tests, was also shown to cause only minimal signal loss for frequencies from 700 MHz to 20 GHz. Indeed, at C-band signal frequencies, the level of insertion loss that it causes is almost imperceptible (see Figure 3). InvisiWave panels can also be sized and finished to blend in with almost any surface and material.
Wireless carriers are racing to quickly make use of their substantial investments in C-band 5G spectrum. Although retrofitting existing macro cell infrastructure is a logical approach, it is not trivial. Carriers need to look at any concealment materials used in those sites to be sure they do not cause unacceptable signal losses at C-band signal frequencies. Companies like Raycap that have considerable expertise in the design and development of materials for macro site concealment can provide guidance when retrofitting existing and designing new macro sites to take advantage of the C-band.
Apostolis Sotiriou is assistant vice president of sales at Raycap.