A WiFi Router, a Soup Can and an Extension Cord Walk into a Bar…

Stacey Black
June 20, 2019
Public Safety

A WiFi Router, a Soup Can and an Extension Cord Walk into a Bar…

I am sure you have heard many versions of the “walk into a bar” joke, but these three characters, once they get together, can cause some real damage to our critical communications networks, such as preventing a 9-1-1 call from going through. Let me explain.

The Federal Communications Commission last fall opened a proceeding to explore the possibility of sharing the 6 GHz frequency band with unlicensed devices, like WiFi routers. As the number of WiFi and other unlicensed users continues to grow, the FCC is, understandably, looking for ways to efficiently share some of the existing spectrum allocations without causing interference to the incumbent licensees and users. However, any sharing in 6 GHz poses a more significant risk than simple interference, as this band is part of the nation’s critical infrastructure. The 6 GHz band carries highly reliable and low latency voice and data traffic from public safety communications systems, as well as data backhaul from thousands of cell sites to the core telecommunications network via point to point, or multi-point microwave links. In fact, AT&T relies on this band to support FirstNet and the first responders that depend on it all around the country. There are over 100,000 of these links in place today covering the entire US (see below).

The importance of preventing interference in this band was not missed by the FCC. In fact, they suggested an interesting approach to avoid interference in the first place and not simply try to mitigate it. They proposed something called an Automatic Frequency Coordinator (AFC) which would have a database of the locations of all the 6 GHz microwave antennas in the country. They proposed that when a future unlicensed device like a WiFi router that is designed to work on the 6 GHz band powers up, it would first connect to the AFC to see if there are any microwave links that are close enough that it might interfere with them. The WiFi router would then only use the frequencies it determined would not cause potential interference. This was a brilliant idea, and the FCC is to be commended for thinking “out of the box.”

Unfortunately, some of the WiFi companies believe it will be too expensive to add this capability to all WiFi routers and are lobbying to restrict the use of an AFC to outdoor units only, citing engineering equations that “most” walls of a building or home are thick enough to dilute the signal and therefore could not cause any interference. Setting aside the affordability claim (recent research indicates 20 billion Wi-Fi devices are to ship between 2019 and 2024, so there are significant economies of scale btw), the issue we have with this logic is how does one keep a WiFi router indoors? Today, there are routers in buses, airplanes, automobiles and patios. What would prevent a residence or business either in a metropolitan area or a rural setting from placing a WiFi router without AFC functionality on its patio and powering it up? The owner of the router would never know it has just impacted the reliability of a microwave link that could be used to save someone’s life when they’re trying to make a 9-1-1 call.

So, back at the bar, one of the three is a WiFi router with a label indicating “For Indoor Use Only” and its owner wants to use their laptop down by the pool. So, the owner invites the extension cord to the party and plugs it in and voila, we now have an outdoor WiFi router fully functioning and capable of interfering. But some don’t stop there, and that is the even scarier situation. In order to get the signal even farther, they invite a tin can (soup, Pringle’s, etc) to the party and attach it to the WiFi router’s antenna. With this threesome, now you have a super-charged WiFi router, potentially capable of up to 10 times the radiated power of the original router. The owner doesn’t know or care if this is legal or whether it harms anyone. To see how prolific this scenario is, search WiFi Boosters or go to YouTube and you will see the hundreds of do-it-yourself ways to increase the power of your indoor WiFi device.

AT&T and other 6 GHz microwave users are concerned about the position the WiFi community has taken on this issue. There is no practical way to prevent so-called “indoor devices” from being used outdoors once they are in the hands of consumers. The only way to protect 6 GHz licensees – and the critical communications needs that they serve – from harmful interference is to require all unlicensed devices capable of operating in the band to use the AFC capability.