OnQ Blog

A new kind of spectrum for new opportunities


Qualcomm products mentioned within this post are offered by Qualcomm Technologies, Inc. and/or its subsidiaries.

Last year, the FCC opened up 150 MHz of spectrum in the U.S. around 3.5 GHz that it named Citizens Broadband Radio Service (CBRS), not to be confused with the old CB radio. Hidden under that name is a novel approach of making more spectrum available when and where it can be used. As spectrum is the life blood of wireless communication, the FCC’s move has the potential to create new wireless opportunities, which for consumers means new and better services.

So what is the new approach in CBRS? First, it enables others to use the spectrum while it is still being used by existing incumbents, such as the military or satellite communication, see Figure 1. This in itself is not new. As a matter of fact, we helped to introduce this concept back in 2013 with Licensed Shared Access (LSA), where a license holder exclusively shares the spectrum with the incumbent. This is a powerful concept that unlocks more spectrum for wireless communication.

Figure 1: When an incumbent like the Navy is using a part of the spectrum, other users need to move to unused portions of the spectrum band.

In addition to sharing with incumbents — CBRS adds a ‘third-tier’ of general usage. In this third-tier, anyone can use the spectrum when it is not used by the higher tiers (the incumbents or users that paid for a license), see Figure 2. Of course, if there are multiple third-tier users in the same area then they will share the available spectrum with each other in a fair manner. The complexity of managing three tiers will require some additional control. To this effect, the FCC has defined a Spectrum Access System (SAS) — a type of database, in effect — and the Wireless Innovation Forum is helping to specify the details to ensure that it all works in accordance with the FCC rules.

Figure 2: CBRS consists of three tiers with different priorities: incumbents, licensed usage (PAL), and general usage (GAA).

So what exciting things will this new kind of spectrum enable? Let’s look at some examples. First it can be used by existing mobile operators to offer Gigabit LTE speeds in more places by making more spectrum available. One can also use this spectrum for small-cell deployments to extend coverage and add capacity indoors. Another example is what we call neutral host, which is a LTE deployment that can be used by subscribers irrespective of their service provider. Such a solution makes sense in places where it is not feasible for each operator to deploy its own radio systems independently; for example, in public venues such as sports stadiums, or in places where it is not cost effective to do so, like indoor coverage in malls or hotels. This approach benefits the venue owner, the mobile operator and the end users. The three-tier approach also enables new entities to offer services by creating their own so-called private LTE networks without owning any spectrum. Such private LTE networks can be used for industrial IoT or enterprise use in general. But let’s not stop there. By enabling anyone to create a LTE-based network, the sky is the limit, literally.

We are not alone at being excited about this new spectrum. Together with five partners we started the CBRS Alliance, which was announced this week, and are working toward field trials later this year. The CBRS Alliance will focus on supporting the commercialization of LTE-based solutions in the CBRS band and is encouraging companies that want to help accomplish this goal to join — for more info see their webpage. From our end, we are getting ready for CBRS by making multiple LTE-based solutions available: LTE-TDD, Licensed Assisted Access (LAA) and MulteFire. Each of these offers different benefits and can co-exist together in the CBRS spectrum. As with CBRS, all good things come in threes!

Patrik Lundqvist

Director, Technical Marketing

More articles from this author

About this author

Related News


5G spectrum sharing brings new innovations

With the acceleration of the 5G New Radio (NR) standards, the interest in 5G shared spectrum grows. The good news is that 5G NR is designed to operate over a wide array of spectrum bands, from low bands below 1 GHz and mid bands from 1 GHz to 6 GHz, to high bands such as mmWave. In addition, 5G NR is also designed to operate across different spectrum types, from licensed spectrum to unlicensed and shared spectrum (Figure 1).

<strong>Figure 1:</strong> Different spectrum types

5G NR promises to support a wide variation of requirements from extreme bandwidth to use cases such as immersive virtual and augmented reality, connecting the massive Internet of Things and enable mission-critical services with sub-millisecond latency. So far, the main industry focus for 5G NR has been on licensed spectrum. It is important, however, to note that access to shared/unlicensed spectrum can extend 5G in multiple dimensions, including enhanced end-user data rates with opportunistic access to more spectrum, more efficient local and private network operation, and new deployment use cases for industrial applications. 5G NR is designed to natively support all spectrum types with the flexibility to take advantage of potentially new spectrum-sharing paradigms, thanks to the design of frame structure with forward compatibility. This creates opportunities for new innovation to take spectrum sharing to the next level in 5G.

For mobile operators, 5G spectrum sharing will enable operators to opportunistically aggregate more spectrum to dynamically support extreme bandwidths for fiber-like experiences. Additionally, 5G spectrum sharing can extend the benefits of 5G NR technologies and the ecosystem to entities that do not have access to licensed spectrum, such as cable operators, enterprises and IoT verticals (Figure 2).

<strong>Figure 2:</strong> Spectrum sharing is valuable for wide range of deployments

Qualcomm Technologies is already pioneering spectrum-sharing technologies in LTE with concepts such as:

We are building and expanding on these concepts in 5G NR, and yet adding innovations around new spectrum-sharing paradigms. So what are these new innovations? As already mentioned, a main disadvantage of unlicensed/shared spectrum is the lack of QoS guarantee. Concepts such as QoS are nowadays taken for granted in licensed spectrum, but are more challenging when sharing spectrum. As such, some of the innovation is focused on making spectrum sharing operate robustly to approach the predictable performance of licensed spectrum while maintaining the flexibility.

Another area of innovation is to improve the overall spectrum utilization when sharing the spectrum among multiple deployments. This can be achieved by dynamic listen-before-talk at lower loads, since collisions are less likely and gains are seen from trunking efficiency over a fixed-resource partition when combining traffic in the same spectrum. At higher loads, however, achieving higher performance with dynamic sharing over a fixed-resource partition is more challenging due to more collisions. This is another area for new innovation that, with a clever coordinated sharing mechanism, one can achieve significant performance merit with dynamic spectrum sharing across loading conditions as illustrated by our early simulation results (Figure 3).

<strong>Figure 3:</strong> Simulation results from spectrum sharing in an indoor scenario with two deployments

This week we announced a 5G NR spectrum-sharing prototype system (Figure 4). We will use this testbed to both drive and track 5G NR standardization in the area of spectrum sharing. Next year, the focus of the testbed will be on technology development, but we are already planning to follow up with field trials with industry leaders. This testbed adds to our existing 5G NR sub-6 GHz and millimeter wave prototype systems. We are excited to bring additional innovation to 5G in the area of spectrum sharing and we see a lot of potential for 5G to leverage all spectrum types in both licensed and unlicensed as well as new shared-spectrum paradigms. To learn more about 5G shared spectrum please visit our webpage.

<strong>Figure 4</strong>: NR spectrum-sharing prototype system