Software-Defined Radio May Cause FCC to Restrict WiFi Modifications

By Wayne Rash  |  Posted 2015-09-08 Print this article Print
Software-Defined Radios

NEWS ANALYSIS: While the concept of a software-defined radio may sound like confusing techno-babble, such radios are almost certainly in devices you already use especially WiFi routers.

The comment period for the Federal Communications Commission's notice of proposed rulemaking (NPRM) on software-defined radios was supposed to end on Sept. 8. But the FCC has extended the comment period because the topic is complex, and the parties involved need time to work.

This NPRM, FCC 15-92, attracted little attention when the agency issued it in July. The reason is that very few people understood what was going on deep inside the new regulation.

What's inside that matters to you is that the FCC is proposing to add new restrictions to those SDRs I mentioned before. Those SDRs are in your cell phone, your tablet, your WiFi equipment and many if not most wireless devices you use on a daily basis.

The radios that connect you to the cellular network or to WiFi are called software-defined because their operational characteristics, including the frequencies at which they operate and the transmitter power that they use, are controlled by software.

Most of the time those software settings come from your mobile carrier, which tells your phone what frequency to use and how much power it should use to connect to the cell tower.

Other times those settings come from software embedded in memory in the device itself. Most of the time you can't do anything to change those settings. But in one specific case you can and it's causing problems.

The area where SDRs are causing the most concern are in WiFi routers. Those routers each have several radios for different frequency bands and for things such as beam-forming. Those routers come from the factory with software that can be modified, either through console settings or by re-flashing the memory. Some of those software packages are from third parties and many of those are open source.

In some cases, either through console settings or through re-flashing, the operating parameters of the WiFi radios can be changed, as can other characteristics of how the router works.

But when the radio operating parameters are changed, it can be possible to modify the settings so that the radio no longer meets FCC certification. That can happen when the router's radios are changed so that they put out too much power or so that they operate on frequencies not approved in the U.S.

While this sounds like an obscure engineering problem, it's not. One area where unauthorized modifications to WiFi have already caused problems is at airports, where WiFi used in the terminals has been interfering with the FAA's Doppler weather radar. As you might imagine, the FAA was alarmed at this because its Doppler radar is a critical tool in monitoring local weather hazards which is important for maintaining safety in the air and on the ground.



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