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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.
Software-Defined Radio May Cause FCC to Restrict WiFi Modifications
Because the radar uses echoes from things such as rain or even moving air, the signal levels are very low and a WiFi signal in the wrong frequency range or with too much power can wreak havoc.
Properly configured WiFi access points won’t cause a problem with weather radar, but some operators had flashed their WiFi hardware with open source software such as OpenWRT or DD-WRT, and changed the settings on the WiFi equipment so that it interfered.
When that happened the FCC began studying the problem, and developed some proposals for changes to WiFi hardware that would prevent this. Those proposed changes were aimed at both SDRs and for non-software-defined wireless products.
The proposed changes for WiFi equipment would prohibit any changes from what the manufacturer of the equipment had intended, which would have two effects. First it would kill off open-source software projects to develop new approaches for WiFi hardware. Then it would make surplus a great deal of WiFi hardware for which the manufacturers had stopped developing updates (which is almost all of it).
The WiFi software industry pushed back against the proposed changes, which is one of the reasons that the comment period is being extended. What’s happening now is that the FCC is trying to develop rules that would put some restrictions on what SDRs are able to do, such as limiting how much a device can be modified in terms of frequency range or power, while also allowing other parameters to be changed.
What this ultimately means is that you should be able to modify how your WiFi routers work while not letting you make them operate illegally at excessive powers in unauthorized frequencies.
This can prove to be especially important in industrial applications where it may be necessary to limit how WiFi works in conjunction with other known equipment ranging from security hardware to manufacturing machinery.
In addition, it means that your company can avoid the capital loss of having to throw away WiFi equipment simply because the manufacturer doesn’t provide updates for security or new operational requirements, such as better support for IPv6 or more effective packet sizing, because you can install open source software to provide those capabilities.
Either way, the changes proposed by the FCC can go a long way to helping you protect your investment in wireless networking, while also avoiding problems caused by interference. The comment period now ends on Oct. 8. It’ll be interesting to see what the FCC decides when it’s over.