On April 28, 2016, the FCC released its Second Report and Order to create the Citizens Broadband Radio Service (CBRS) in the 3550-3700 MHZ (3.5 GHz) band, making available 150 MHz of spectrum for mobile broadband and other commercial users. The spectrum sharing structure advocated for CBRS is an opportunity for the U.S. to showcase a novel approach to using spectrum. Pulling it off will require innovation on a number of fronts: technology, business models, and intra- and inter- industry cooperation.
The 3.5 GHz band, held by the Department of Defense and fixed satellite service providers, has been underutilized in recent years. There has been a movement to open up the band and make it available for shared use between government and commercial interests, provided the incumbents are given the proper protection. 3.5 GHz services will be primarily unlicensed or ‘lightly licensed’ services, in that an operator will not be required to buy and permanently own spectrum. The spectrum sharing scheme will feature three-tiered access system: Incumbents (existing DOD & satellite users); Priority Access Layer (acquire spectrum for up to three years through an auction process); and General Authorized Access (any user with an authorized 3.5 GHz device). The Spectrum Access System (SAS) will be a database operated by anywhere from two to four private companies.
CBRS is exciting because it makes available a substantial amount of spectrum without the need for expensive auctions and not tied to a particular operator. A leading use case for CBRS is for improved in-building coverage and capacity augmentation using LTE, with the advantage of a more WiFi-like business model and economics. More relaxed power requirements in the recent FCC Order also make CBRS use possible outdoors.
I am excited about CBRS because it represents an opportunity for the U.S. to demonstrate technology, business model, and regulatory/industry innovation. Spectrum, the scarcest resource in mobile computing, would be used in a much more efficient way. Developing and deploying an effective spectrum sharing mechanism would be an important achievement. Another area of technology innovation will be the ‘sensor networks, operated by Environmental Sensing Capability (ESC) operators, to make sure incumbents and others utilizing the spectrum are protected from interference.
CBRS also presents an opportunity to figure out the right business model for in-building wireless solutions. A major inhibitor to better indoor coverage has been that current small cell systems are generally tied to a particular operator, making them expensive and difficult to scale. CBRS offers the potential for ‘neutral host’ solutions at an enterprise level. This could lead to creative cost-sharing structures between companies/building owners and mobile operators or other entities. The ability to acquire ‘temporary’ licenses also provides for some new use cases. For example, event-driven capacity and coverage augmentation.
Also innovative is the potential for intra-industry cooperation. A fairly broad ecosystem of support is building for CBRS. This includes both RAN equipment leaders (Ericsson, Nokia), and also key WiFi suppliers (Cisco, Ruckus Wireless), major internet players such as Google, and startups such as Federated Wireless, who are developing the spectrum sharing databases and sensor networks.
Successfully implementing CBRS will also require a unique level of public-private cooperation. The FCC and the industry will have to work closely to ensure proper development and implementation of the spectrum sharing scheme. Incumbent users of 3.5 GHz channels will have to get comfortable with the idea of sharing the spectrum with private sector entities. One issue that remains controversial is the requirement for ‘exclusion zones’, which protect the incumbents within a certain radius, and near coastal areas. The current proposal for these exclusion zones would make it hard to implement CBRS in certain cities. Clearly, this needs to be resolved.
The next year or so will be fairly critical in determining whether this ambitious proposal will become reality and when services might become available. Google is running a test in Kansas City this summer and is also one of the SAS candidates. The FCC must review and determine who will operate the SASs. Business cases need to be refined. The technology for the sensor networks must be vetted and issues pertaining to the exclusion zones must be resolved.
This is leading-edge stuff. With CBRS, U.S. companies, industry, and regulators could provide a showcase for how wireless’ scarcest and most valuable resource — spectrum — can be more effectively utilized in the future.