Potential Expansion of the 3.65 GHz Band: More Opportunity? More Risk?

The demand for wireless broadband has exploded in recent years, but what impact will this have on the energy and utility industry as it continues to build the critical infrastructure to efficiently, reliably, and safely run the grid?

Some of this growth in wireless broadband has been driven by the desire for mobile data or internet access in regions not easily reached by copper or fiber solutions, but there has also been a growing use of wireless for critical applications by energy and utility users. Some common utility applications using this connectivity include video surveillance of critical facilities, real-time SCADA monitoring and control, and system protection.

The lightly-licensed 3.65 GHz band has become popular for a variety of point-to-point and point-to-multipoint solutions. One common network architecture for electric utilities is to use the fiber that connects major (transmission) substations as a backbone and then use 3.65 GHz wireless to reach smaller (distribution) substations and other devices (such as reclosers and capacitor bank controllers) that do not have fiber connectivity. In fact, this type of application has made electric utilities one of the key users of this spectrum when it comes to deploying private networks (i.e., those not offering internet connectivity).

For some time now there has been talk about making additional spectrum available at 3.5 GHz, but there have been different opinions on how this could best be used.

The current 3.65 GHz band is lightly licensed and subject to a minimal amount of regulation. While some feel that licensed and dedicated spectrum is “best”, the reality is that a wide variety of users have been able to successfully share use of the 3.65 GHz band for a variety of applications including internet access, video surveillance cameras, and, in the utility space, substation communications. Many of these users were hoping to see the 50 MHz of spectrum they currently have access to expand by another 150 MHz at 3.5 GHz.

The FCC had discussed auctioning the spectrum and carriers, understandably, expected a degree of exclusivity in return for paying for the spectrum. Most carriers have expressed interest in using spectrum around these frequencies to build “micro-cells” that would allow them to provide high-speed Internet access and related services in focused areas.

In this landscape, the FCC has looked for creative ways that balance the expectations of bidders if the spectrum is auctioned with allowing something similar to the lightly licensed access of the 3.65 GHz band in areas where the new spectrum might be underutilized. What they proposed was some type of Spectrum Access System (SAS). The idea was that the SAS could allow orderly sharing of the new spectrum (with priority given to primary access licensees who paid for the spectrum).


Those interested in bidding had concerns about this. A similar approach has been used for TV white space—the spectrum freed up as over-the-air television broadcasts evolved from analog to digital modulation.  In that particular application, discussions started before 2007 and commercially viable solutions have only recently come to market.

Potential bidders for the spectrum were obviously concerned about encountering a similar delay in commercially viable technology. Bidding for a five year license on a chunk of spectrum makes little sense if the technology that allows use of that spectrum might not even be developed within the period of time covered by that license. As an alternative, they have proposed (and the FCC seems to be moving forward with) an approach where roughly half of the spectrum would be dedicated for use by the successful bidder and the other half would be where some type of SAS solution could be developed over time.

Utilities around the country are using the current 3.65 GHz spectrum and it does seem likely that, as new rules around 3.5 GHz emerge, we may soon see changes that ultimately may affect 3.65 GHz incumbents. While significant changes would likely be phased in over time, this and the broader impact of wireless broadband are areas utility telecom leaders need to watch closely and make their voices heard.

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