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Ars Technica has an article about Linksys committing to maintaining open source firmware usage for the WRT series of routers. This is a follow up to a previous story that ran when the original announcement regarding FCC (Federal Communications Commission) enforcement of 5.8 Ghz part 15 device requirements came out. At least there remains one well known product that decided to implement the requirement in a way that is consumer modification friendly. From the article:
Any 5GHz routers sold on or after June 2 must include security measures that prevent these types of changes. But router makers can still allow loading of open source firmware as long as they also deploy controls that prevent devices from operating outside their allowed frequencies, types of modulation, power levels, and so on.
This takes more work than simply locking out third-party firmware entirely, but Linksys, a division of Belkin, made the extra effort. On and after June 2, newly sold Linksys WRT routers will store RF parameter data in a separate memory location in order to secure it from the firmware, the company says. That will allow users to keep loading open source firmware the same way they do now.
[Continues...]
Though I disagree with this notion
Although Linksys has proven that open source firmware can still be used under the new FCC rules, it's clear that options for open source users will be more limited than they are today. Kaloz wishes the FCC had taken a different approach, one focused on punishing people who cause interference without preventing legitimate uses of network hardware.
Is the suggestion that the Doppler weather radar in use at airports is less important than getting cat pictures from the comfort of your couch and not having to run an extra Ethernet cable? Because Delta Flight 191 is why these airport Doppler weather radar systems exist at all. Do we punish before or after the crash? As well I don't think there is an appreciation for just how hard it is to find malfunctioning transmitters: it can be done but with significant amounts of work. The FCC is not funded for this level of enforcement right now. Everyone must share the very finite electromagnetic spectrum. I don't have a problem giving life and safety critical systems priority over cat videos.
As a quick experiment locate your WiFi router and check the verbiage. I'm sure everyone has seen the part 15 text but probably never paid attention to it. You will find This device may not cause harmful interference as well as this device must accept any interference received. That's because the weather radar, by design, gets to break you but you don't get to break it.
(Score: 2) by Rich on Saturday May 14 2016, @09:20PM
Could anyone with a solid understanding of the physics enlighten me a bit? As I understand it, with an omnidirectional antenna (as routers should have?!), the radiated energy evenly spreads into three dimensions. Therefore, reception energy at a certain distance would be the product of the radiated energy times the third root of the distance to the receiver.
Which would mean, even at the maximum power the antenna drivers can cope with (in the tens, or maybe low hundred milliwatt range), the effective range of the sender would be hardly larger (e.g. much less than a magnitude) than at its regular power. So moving the router closer to any "threatened installation" would be much more of a danger than the piddly increase of broadcast power?
Do I misunderstand that, or is it in fact like I imagine?
(Score: 3, Informative) by c0lo on Saturday May 14 2016, @10:04PM
It's only square root - Gauss law says that the flux of energy from any closed surface matches the total energy emitted. As such, if assuming the energy distributes evenly of the surface of a sphere sphere surrounding the emitter, as the surface of the sphere increases with the square power of its radius, the flux received by any surface element of that sphere decreases with the square root of the radius.
Some more detalls:
1. the energy is also absorbed, so you want to modulate the square root formula with an exponential decay. Not much of absorption in pure air but it will be non-negligible for a rainy day
2. it's very easy to transform an omnidirectional router in an unidirectional one: see cantenna [wikipedia.org]. I imagine that if the emitted power level and frequency can be varied, a router could be easily and cheaply modified into a jamming device.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Rich on Sunday May 15 2016, @02:21AM
Ah yes. I mixed that up with the nuclear blast calculations we've got to deal with from time to time on here; there the energy gets absorbed along the way, while radio waves (mostly, with your mentioned exceptions) flow freely and only spread out on the growing sphere (or whatever pattern a particular antenna gives). Obvious in retrospect.
Now, to put the numbers together, do you (or anyone reading) know what power limits are imposed by the software and what power the chipsets (or complete routers) are actually capable of? That'd give us a grasp on the actual severity of the issue; even with "only" square root distance and the exponential decay, a fourfold increase in power would less than double the range, which i wouldn't consider very frightening, given that WLAN already degrades when moving two rooms away from the AP.
(And no, Pringles cantennas don't count in the calculations, as they're not covered by the software limitations we discuss here : )
(Score: 2) by Scruffy Beard 2 on Saturday May 14 2016, @10:10PM
Real antennas are not isotropic. The antenna "gain" you see on data-sheets refers to how much the antenna radiates in a specific direction over an isotropic antenna.
And the received power diminishes in proportion to the surface area of the sphere of radiation, not the volume.
(Score: 2) by Runaway1956 on Sunday May 15 2016, @12:40AM
An omnidirectional antenna's broadcast pattern is more like a donut than a sphere. That is, the base and the tip if the antenna don't transmit as much as the length of the antenna. But, visualizing the broadcast pattern as a sphere isn't going to make a huge difference to your statement.
(Score: 3, Informative) by VLM on Sunday May 15 2016, @12:36PM
That's not too far off but there's other problems.
One is relative distance problems. So one due with a bluetooth earpiece 100 feet away from the dish at the nexrad site has a zillion times stronger signal than someone 30 miles away (probably below the horizon) with a 30 dB illegal amplifier. This comes up a lot with "RF causes teh cancer" discussions where the RF from a neuron a tiny fraction of a mm away is much stronger than a phone a couple inches away.
Another problem is freq band, I mostly use 5 ghz at home because my phone and access point support it and it seems much less congested. There is a small problem with interfering with nexrad in that nexrad is "S-band" and my home wifi is I guess in "C-band". As a side note its funny that when I started out in electronics all the textbooks and stuff were apologetic "sorry about using the legacy WW2 classified radar band names but that was only 30 years ago so gimme a Fing break" and here it is 2016 and people still drop band names in casual conversation. Anyway, much like an AM broadcast transmitter doesn't interfere too much with TV reception or whatever aside from anecdotes about front end overload or IMD products, there isn't a very serious concern. Like two airplanes crossing paths but one is in the landing pattern at a thousand feet over the airport and the other is passing thru at flight level 350, there really isn't a serious danger of collision.
Modulation is an issue. The nexrad scientists have a fascination with weird polarization, and your wifi is unlikely to be interesting. "unjamable" military spread spectrum radar works about the same way. I donno the nexrad modulation scheme and filtering scheme but its probably too smart to jam. Remember, wifi and microwave ovens and ISM band in general was not invented yesterday although thats a journalistically useful false belief. Its not a new issue and not a real problem.
Technical skill is an interesting problem. Most people dumb enough to break the law and use illegal amps instead of better antennas are probably too dumb to use the amp correctly and are going to distort the output such that they get a very loud unusable signal, which makes the problem kind of self limiting. The problem with CB linears is the modulation scheme and general technology is tolerant of shitty amp design making cheap interference producing CB linears a profitable industry sector. Not so much wifi, for a variety of boring EE reasons. You can't just stick an old bipolar transistor biased class C on a wifi and expect to decode the other end, just don't work that way.
The final problem is directivity. If your antenna can point down to a fraction of a degree like a nexrad, the worst a non-military attacker can do is make a funky looking spear along that one specific bearing. If you have megawatts and billions of dollars budget THEN a military ECM pod can generate insane interference levels at megawatt power outputs to make noise on the radar. I could try to jam my local nexrad and I've got the gear and knowledge to do it but it'll show up as a line going over my house when they zoom in... how long would I last, maybe a couple hours or days at most? And operationally a line does nothing. If you have a team of a hundred jammers working together probably half are FBI or Saudi agents anyway so you got non-technical issues. Its just not feasible as an overall systemic attack.