Midband spectrum is widely recognized to be the sweet spot for 5G deployments globally, due to its combination of large amounts of available bandwidth and better propagation characteristics than millimeter-wave. In the past year, the US Federal Communications Commission has auctioned the 70 megahertz of CBRS Priority Access Licenses, plus another 280 megahertz of C-Band spectrum that will begin coming online late this year and is teeing up 100 megahertz of additional midband spectrum at 3.45-3.55 GHz, just below the CBRS band, with the auction set to start October 5, 2021.

In total, that means that at the end of this year, the FCC will have opened up 530 megahertz of midband spectrum (auctioning 450 megahertz of it) and 250 megahertz will be available for use, with the rest coming online in the next few years. In the context of all that new spectrum, STEPHEN RAYMENT  shares with RCR Wireless News  over email about trends and activity in midband spectrum in the United States, writes Kelly Hill.

RCR WIRELESS: How are you seeing CBRS being used? Primarily by carriers for capacity augmentation, for FWA or for private networks? Do you expect to see that mix change over time?

STEPHEN RAYMENT: CBRS is being used for all mobile broadband and Fixed Wireless Access public as well as private networks, delivering indoor coverage and network capacity. So all use cases are what we can imagine. The usage variations come from different provider or enterprise strategies and their current spectrum holding or lack thereof. In that sense, CBRS is general-purpose in nature, with over 140,000 radios deployed to date. It is difficult to say which use case will dominate over time as we are still in the early days, e.g. with PAL only recently starting to actually deploy.  But generally we would expect use in all dimensions to continue to grow.

RCR: How do you think that C Band deployments will change 5G in the U.S.? In what timeframe (2022? ’23? Beyond?)

SR: The first 100 megahertz of C-Band spectrum becomes available in December of this year, however, deployments have already started. The next 180 megahertz becomes available in December of 2023. C-Band will help deliver the true promise of 5G by providing the ideal mix of coverage and speed. This will start in 2022 and grow further in 2024. In short, “true” 5G will become evident to more people going forward.

RCR: What will midband indoor infrastructure needs look like? Will it need dedicated systems or will it provide sufficient coverage outdoor-in?

SR: A lot can be done out-to-in with mid-band. That being said, mid-band is not as effective as lower bands for out-to-in. So it is likely that indoor solutions will need to grow. But we can say interest in indoor solutions continues, looking at both mid-band and mmWave spectrum. And mid-band and mmW small cells systems will be best-equipped to deliver indoors, replacing or augmenting DAS systems which will struggle to deliver the higher frequencies involved.

RCR: In LTE, as the technology evolved and more people made use of it, carriers had to make a massive effort to upgrade backhaul capacity, and they also had to deal with issues like PIM in the lower bands. Do you see any similar challenges ahead for 5G and midband spectrum? Or has the industry learned lessons from 4G that they’re applying now?

SR: With the basic rule that 5G is 10x 4G, it would be unrealistic to say nothing is needed to manage this growing backhaul capacity. However, a lot of the work has been done over the last years, so in that sense, the needs in terms of throughput and latency are well understood. It will also become important as we move to higher performance indoor networks

RCR: Verizon recently asked for permission from the FCC to tune its C Band deployment model. Shared CBRS spectrum is still somewhat of a novelty and has only been fully licensed for a relatively short time. What are the details of midband spectrum behavior that operators and equipment OEMs still need to understand to rapidly and efficiently plan and deploy these networks?

SR: CBRS shared (GAA) and licensed (PAL) spectrum are being deployed and used already. Perhaps what will continue to evolve over time are the techniques used for sharing, how adjacent users impact each other and how incumbent detection can be improved. The latter is one item under a lot of discussion recently. So the basics are there, and plans are well understood, now with execution, we expect there to be learning based on real life behaviors. Our recent first call announcement of 5G NR in CBRS with C-Band is an important step in bringing the benefits of New Radio to CBRS along with C-Band.

RCR: What other emerging technologies (Open RAN, vRAN, MEC, etc.) are also emerging that you think will impact how midband spectrum is deployed in the US?

SR : 5G itself is a tipping point. But then, in addition, we see other tipping points in the industry with the introduction of O-RAN, vRAN, hyperscalers, MEC. Many happening at the same time. These are frequency independent. But, that being said, generally introduction of major new technologies need a trigger, and that trigger is typically major new spend, like is happening for C-Band. So it is true, C-Band is a good target for all of these and the interest is such. The challenge is readiness and timing, not necessarily from vendors, but for specifications in the case of O-RAN and whether CSPs are ready for things like vRAN, hyperscaler use, credible use cases for MEC. So the timing will be different for every provider based on their particular situation and vision. One would naturally expect more traditional deployments in the early stages of C-Band and then the introduction of alternatives as noted in the coming years. We are ready for all.