CBRS Opens-Up 3.5 MHz Mid-Band Spectrum to New Users

Last week, we saw the formal start of Initial Commercial Deployment (ICD) of the 3.5 MHz Citizens Broadband Radio Services (CBRS) spectrum band in the US. The CBRS band is a 150 MHz slice of spectrum available for use on a shared and unlicensed basis. The spectrum is divided into three tiers – Tier 1, which is used by incumbents such as the Navy, Department of Defense and by military satellites, and two lower tiers, which are allocated for commercial use (Exhibit 1).

Applicants can apply for a Tier-2 Priority Access License (PAL), a renewable 10-year license to use one or more 10MHz channels within the 3,500-3,650MHz portion of the band, in a limited geographical area. They can also apply for Tier-3 General Authorised Access (GAA), which is unlicensed, like Wi-Fi, and provides a dynamic allocation of the available 100MHz channels so that access does not interfere with communications in the two upper tiers.

Certification and full commercial services are expected to start in Q4 2019 after the 30-day ICD period is successfully concluded. To date, only GAA licenses have been issued, and the auctioning of PAL licenses is not expected until mid-2020. Further, 5G shared spectrum services are also scheduled to begin in 2020 following the publication of the CBRS Alliance’s Release 3 specifications in Q4 2019.

The CBRS 3-tier Spectrum Sharing Architecture
Picture Credit: Lanner

Exhibit 1: The CBRS 3-tier Spectrum Sharing Architecture

The major attraction of the CBRS band is that it will allow a wide range of companies – from cable companies, wireless and fixed telecom operators to a host of commercial and industrial companies – to develop, build and operate their own wireless networks without the involvement of the “Big 4” mobile operators. For example, the CBRS band can support business models for indoor, small cell deployments funded and owned by enterprises themselves. Meanwhile, GAA licenses are especially well-suited for private networks as they combine the best of both LTE and Wi-Fi networks, i.e. they offer traffic management, security, reliability plus low latency.

Companies eyeing opportunities in this band include Amazon, Google, Motorola, and Nokia as well as many industrial enterprises looking to use the spectrum to build LTE and later 5G private networks for IoT, IIoT (Industrial IoT) and other applications.

Amazon has tested a private IoT network designed to support devices such as real-time surveillance cameras and smart meters, with several partners. Federated Wireless, cable company Charter Communications, and Landmark Dividend want to build private LTE networks while Motorola wants to use the band for its MotoTrbo service. Other companies involved include Google, Facebook, Nokia, and Microsoft, as well as Walt Disney Parks and Resorts.

The ‘Big 4’ MNOs are also heavily engaged as the band will enable them to increase capacity by combining transmission in the CBRS band with other licensed spectrum bands via carrier aggregation technology. They could also use CBRS to boost their network performance by using it as a kind of interim low latency alternative or complement to Wi-Fi prior to the widespread deployment of 5G. In-building CBRS networks will also likely be connected to the operators’ public 5G networks for seamless interoperability.

Verizon is particularly keen on the band. Although it owns significant amounts of mmWave spectrum, it lacks sufficient mid-band spectrum and has been testing both commercial and private mobile networks for several months, particularly the use of indoor/outdoor small cells. The company is already offering CBRS-capable devices to its customers, including the latest Apple iPhone 11 handsets, Samsung Galaxy S10 and Google Pixel 3. Meanwhile, AT&T is keen to use the band for fixed wireless Internet services to rural customers and expects to start services in late Q4 2019.

Although there is tremendous interest in using the band, ultimately, its success will depend on a number of factors. Top of the list, however, will be the ability of the spectrum sharing system (administered by Federated Wireless, CommScope, Google, and Nokia) to protect the access of Tier 1 incumbent users. Although multiple trials have taken place, it will take some time to determine whether spectrum sharing works as envisaged. If it does not, then this is potentially a major issue, as most of the Tier 1 users are located along the US coastline, where the majority of the population live and where the demand for CBRS spectrum is likely to be highest.

Pioneered by the Federal Communications Commission (FCC) and commercial US wireless companies, the CBRS dynamic spectrum sharing model is being closely watched by regulators around the world. If successful, it will likely be implemented outside the US. Together with other similar systems under development elsewhere (such as ETSI’s Licensed Shared Access), spectrum sharing could potentially open up swathes of lightly used spectrum bands around the world for new applications. Counterpoint Research believes that this will dramatically change the wireless landscape, for example, by accelerating the deployment of wireless networks by non-MNO companies.  In future, dynamic spectrum sharing is likely to become the norm rather than the exception in underutilized and unlicensed spectrum bands, but is unlikely to be used in mobile licensed bands.