DOD vs. 802.11b

goombah99 writes "The NY times (reg required) reports that "The Defense Department, arguing that an increasingly popular form of wireless Internet access could interfere with military radar, is seeking new limits on the technology". It would seem they have a good point; radar is an essential for both defense and civilian aviation as well as ship navigation in tight quarters. Critics of the restrictions contend technology can limit the interference, but what proof is there to these assertions? Sure we all want wireless internet but maybe there should be more careful review of its consequences."

Comments

fear mongering

[dbrower]

it's not about current wifi, but about expansion into the 5ghz band being debated. there are no current examples of interference.

-dB

Re:fear mongering

[stinky wizzleteats]

If he had gotten up and actually acted, the planes would have been followed by fighter planes, and given authorization, shot down before they got close enough to take out the towers.

I notice your conspicuous use of the plural term "towers" above. Do you honestly mean to suggest that on the morning of 9/11, before the first tower was struck, it was appropriate and justifiable behavior to shoot down airliners that were flying off-course?

Let's take the discussion further. Let's move to just after the first plane crash. Do you expect the president of the United States to authorize the destruction of every airliner in U.S. airspace which is off-course because one happened to run into a building?

I don't know what a careful decision on the part of the Commander in Chief to use deadly force against innocent civilians looks like in your political universe, but I sleep better at night knowing that my president is reluctant to take such action.

Concerns

[coreman]

Well, they'd better tighten up the radars to deal with it else they've just given an off the shelf solution to interfering with these radars, and told interested parties about it.

Consider the impact of a Beowulf cluster of these!

Why not just use cell towers for radar?

[guacamolefoo]

Recently in the ex-Yugoslav mess, I believe that there were reports of the use of cell towers to track the "stealth" bomber, so who needs radar? Besides, is the DOD planning on bombing Starbucks? One can only hope!

GF

Interference?

[wiredog]

Don't wifi/802.whatever/etc have power outputs in the milliwatts? Military radars work with hundreds of watts.

And if these technologies do jam radars, is there an application in the field of speeding ticket avoidance?

Re:Interference?

[voodoopriestess]

Most modern radars have attenuation and can handle a wide range of RF frequencies. This can be from 0.5 GHz to 40 GHz. Mobile phones and current WIFI inhabit the 2.5 GHz range (commonly refered to as CD band) and is dealt with seperately to the rest of the microwave bands (E-J and K). A WIFI adapter will NOT jam a military radar but rather show up as an unknown emitter which in a time of war will generally cause the ship/plane/helicopter to go "defensive" and defend against the potential threat!

FCC should take care of this

[spacecomputer]

Last I checked it was the FCC that was responsible for the allocation of spectrum in the United States and territories. They are the arbitrator of interference issues. In short: I use WiFi, if there is a problem then the FCC, not me, is to blame.

Re:FCC should take care of this

[Qzukk]

What is the military complaining about, doesn't their equipment have the FCC stamp on it?

The military version of the FCC stamp reads "This device must accept all interference, and is permitted to fire missiles back."

Typical Military BS

[Boulder Geek]

Choice quotes: "might cause interence", "not right now, but maybe in the future"... This is the Pentagon spreading FUD, and knowing the predilictions of the current administration, it all bodes very ill for wireless in general and WiFi in particular. In my quick scan of the article I didn't see any mention of 5Ghz or 802.11a, so it rationalizations that the Pentagon is looking at the UII band are misplaced.

Consider yourselves warned.

This is about 5Ghz technology

[goombah99]

Despite the misleading headline inserted by slashdot editors, the article refers to an"increasingly popular" wireless technology in the 5Ghz band.

The pentagon is not trying to poop on the wifi party. And they are not out to supress info transfers. They just want to make sure that a stupid irrversible giveaway of the wrong band does not take place. Apparently a lot of next generation radars need this band and depend upon a noise free environement. for example the article notes weather radar. Believe me getting a radar return of gas is very very difficult. Even high power radars are not the whole answer--the return signals are weak and fall off 1/r^2 limiting the range.

My fear is that the bush admin will give way to the coroprate interests. Microsoft is one of them mentioned in the article. these companies have dumped tons of money into campaign contributions. And the easy thing for the bush admin to do is to do nothing at all.

regardless of your misgivings about the department of defenses other activities, having good radar is a swell idea that we all can benenefit from.

presumably there might be some techno fix that could make all happy. But remember these radar systems take years to design. Its not just about making the latest up-to-date technology but also about quality assurance, standards and interoperability. So just saying they could be redesigned is not a valid response. You dont retrofit safety systems on a whim because some thinks they can make it better. Murphy's law will get you. And its often better to have standardized less than state of the art systems people know the limitiations of than a myriad of superior technologies they dont know the relaibaility of.

Re:This is about 5Ghz technology

[archeopterix]

Shouldn't it show the DoD that they should start work, today, on the next-next generation of radar, which won't be able to be foiled by a bunch of high-power 5 ghz transmission devices, the basic parts for which might soon become available from civilian outlets over the Internet.

It's not that easy to jam a radar. Bats are a living proof of this. Thousands of them can navigate in dark caves without jamming each other. Radars are designed to avoid jamming - they use quite a wide spectrum of radio waves that changes dynamically (bats do that too, only with sound waves). Of course it is probably possible to build a jamming system, but such a system would involve many high-powered transmitters and thus would be very costly. I guess that widespread use of radar-frequency Wi-Fi would just slightly degrade military radar performance (perhaps civilian aviation radars would suffer more) and that's what the military are concerned about. I would be more concerned about a kilowatt radar signal damaging Wi-Fi equipment though.

Re:Other problems as well

[aborchers]

Interference of cell phones with avionics is a red herring. The real problem with using cell phones on airplanes is that at high altitude and speed, a cell phone hops towers too frequently.

The case for avionics interference is actually quite weak, from all reports I've heard. The policy for cell use on aircraft is partly CYA, partly greed (use our in-flight phone instead) and partly a cookie to the cell industry, which cannot or does not want to deal with the hassles of supporting high-speed tower-hopping on their networks...

Home radar jamming?

[OYAHHH]

I've,

Done a lot of civilian radar track data analysis and I can tell you that radar data is already littered with LOTS (and I mean LOTS) of inaccuracy.

I've seen cases where the data loss was so bad that I can hardly imagine the situation where joe-schmoe-bin-ladin with his laptop and homemade radar jamming equipment could make it any worse.

It's one of those situations where if you knew what the ingrediants were you might not want to eat it.

I certainly don't have a problem with the DOD wanting to limit radio encroachments into vital wavelengths.

But, sometimes I get the feeling that the military is crying wolf when the wolf has been there the entire time and nobody in the know is brave enough to admit it.

Re:Baloney!

[krlynch]

More likely than ignorance, they (DOD scientists and engineers) are probably concerned that this new use of spectrum previously allocated for air traffic control, weather data collection, and defense purposes will cause problems for OLD radar equipment that IS NOT capable of changing frequencies. You know, the backwards compatibility problem. There are billions and billions of dollars worth of government (military and civilian) radar systems that could be affected, and no one is talking about paying to replace or upgrade those systems to eliminate the potential for interference.

Reading (somewhat between the lines of) the article, I find explicitly or implicitly the following points:

• There exist critical radar systems for civilian and military air traffic control, as well as weather radar that CAN'T change the frequencies they are operating on.
  
• The spectrum they have been allocated and are currently using is a logical location to put new WiFi capabilities, in geographic areas where they won't cause radar interference.
  
• In areas where there is potential for interference, the manufacturers of new WiFi gear have designed their new systems to choose spectrum such that they don't interfere with those radars, in anticipation of those spectrum bands becoming available for such use.
  
• The DOD is concerned that these designs do not provide sufficient guarantees that they won't cause the interference DOD is concerned about
  
• The industry is unwilling (either because they don't think it is necessary, or they don't want to spend the money ... take your pick) to go back to the drawing board and make stronger signal isolation guarantees.
  
• The two sides are lobbying the FCC to see the truth of their beliefs.
  

I don't see a big conspiracy here ... just two groups of people that don't quite agree with the technical points raised by the other side, and a number of issues that need more study before everyone will be happy.

While I wouldn't mind faster and more capable WiFi, I'd much rather that the tech industry be forced to make changes to ensure that interference won't be a problem NOW than having to do so AFTER someone's web surfing causes a plane to disappear from air traffic control screens ....

Re:Baloney!

[mesocyclone]

Baloney yourself!

Neither software defined radio nor the Open Spectrum initiative renders interference problems obsolete. Saying otherwise is about as meaningful as saying that modern computing repeals the 2nd Law of Thermodynamics!

Radios of any sort increase the energy in the bandwidth that they use. This is true whether they are narrowband traditional radios or ultramodern, cellularized, spread spectrum or ultra-wideband radios of the future.

Any radio receiver has to pull its desired signal out of the ambient noise. That noise consists of natural noise (thermal noise, spherics, astronomical sources, etc) and man-made noise (either noise-like signals or coherent signals). Many radio systems must operate close to the theoretical edge of practicality. The military and reconnaisance organizations especially need to operate with very small noise margins - their ability to do so is one of their advantages.

Increasing the ambient signal levels do degrate the capabilities of these systems. That is trivially proven.

Open Spectrum is an approach to improve bandwidth sharing. That is all it is - it is not a magic panacea that somehow makes interference vanish. Software Defined Radio is simply processing radio signals in software. It also doesn't change the underlying physics.

Consider the issue of radar... radar operates with an inverse-fourth law (the radar equation). The return signal is inversely proportional to the fourth power of the range. Normal radio operates by an inverse square law. Thus radar is especially vulnerable to interference.

To put a little numeracy in here... let's look at a 5GHz space based radar. Assume it outputs 1000 watts peak power (power is very expensive in orbit, you know) from an altitude of 150 miles. Assume the antenna shapes this to 100,000 watts effective radiated power (ERP).

By the time this reaches the earth, it is about 1E-7 watts per square meter. Assume the radar wants to image an area of 100 meters. This is 1E-3 watts or 1 milliwatt. A *single* WiFi stations puts out 10s of milliwatts. Thus if you have one WiFi per 100 square meters, you will have ambient "noise" of 20-30 decibells above the radar signal.

So, this is not a trivial issue. Of course, coherent integration can overcome much higher SNR's, but only at a cost (it requires much more time per resolution area, reducing the overall capability of the system).

In other words, there ain't no free lunch.

The Pentagon has the services of the best experts around to advise it on issues like this. Discounting their objections out of hand is arguing from either ignorance or opinion, not science or engineering. Determining whether their objections are appropriate in this case is a matter for analyses far more complex than will appear on slashdot, and in some cases, probably will require access to very sensitive classified information.

WRONG WRONG WRONG!!! (bzzzzt)

[flatulus]

There is so much misinformation in both the NY Times article and the discussion here on /., I just have to set the record straight:

1) The DoD is concerned about the 5 GHz U-NII (Unlicensed National Information Infrastructure) band -- which is where 802.11a (not 802.11b) operates. This is a recently opened band.

2) There is no way the DoD can mount a plausible objection to 802.11b, as it operates in the 2.4 GHz ISM (Industrial, Scientific, and Medical) band. The ISM band is the home to microwave ovens, which frequently "leak" 30 times more RF than an 802.11b "intentionally" transmits. There are industrial applications of the 2.4 GHz ISM band that emit KILOWATTS of RF. The 2.4 GHz band is, in essence, the junkyard of the microwave spectrum.

3) The IEEE 802.11 committee is already working on interference mitigation techniques to make 802.11 radios more "friendly" to radar in the 5 GHz band. This is the work of Task Group H. The two major innovations being hammered out in that task group are DFS and TPC (dynamic frequency selection and transmit power control). Both of these are mandated by the European Union's regulatory bodies, in order to open up 5 GHz for 802.11 radios. When ratified, this will lead to an 802.11h radio, which is functionally analogous to 802.11a, but with DFS and TPC. At that time it is likely that 802.11a will wither on the vine, being replaced with 802.11h in the U.S. also. (Note: 802.11a is legal only in the U.S. today. And DoD is basically following the EU's lead in expressing concern about interference to radar. That's what the NYT article meant about Europe being "ahead" in this matter.)

4) While the FCC is in charge of CIVILIAN use of the RF spectrum, they are not the sole arbiter of RF in the United States. The rest of the job is done by the NTIA (National Telecommunications and Information Administration), which is the caretaker for government use of spectrum. For the FCC to open up the 5 GHz spectrum, they needed approval from the NTIA first (which they got).

Summary: "But the times they are a' changin."

Basically the DoD is trying to head off proliferation of 802.11a before it's too late. Of course, the market leading vendors (e.g. Atheros) are none too happy about this, and I don't blame them. Changing the rules after they invest many millions in development of a product on the basis of an expectation of marketability would make even the most accommodating entrepreneur cranky :)

How many times do I have to say this...?

[cr0sh]

I have read many of the comments made on this topice here in this forum. I understand that there seems to be a confusion as to whether this issue is related to 802.11a or 802.11b. Frankly, I don't think it matters.

The fact is, 802.11x communication systems ARE REGULATED BY THE FCC. If they chose (or were ordered), they could easily deem the spectrum used by 802.11x to be off-limits to anyone! Sure, I have heard the comments like "but businesses have invested millions in 802.11 - they would howl" - perhaps they might. Or perhaps a transition would occur to make the larger companies happy, by providing some form of wireless that isn't available to the average consumer like 802.11x is - but still gives those communications companies a foothold in wireless comms, while making consumers happy, and also possibly providing an easy place for the feds to tap, while making community nets a thing of the past (think it impossible? Try to buy, as a consumer, your own TXRX system for a cell phone - good luck, if you can even afford it). Everyone (mostly) wins - except for the citizen, ne - consumer...

I have said many times that the government has this (unelected, unrepresented) power via the FCC to do this (think I am joking? Do a search on my past comments, if you don't believe me). In these same comments, I have presented a solution that very few have worked on (at least on the homebrew front), that could keep community networks alive, a solution the government (FCC) cannot regulate (but oh how they would try - and if they succeeded, well - then that is the cue for true revolution):

Laser/LEDComm

I daresay RONJA is probably the most advanced "homebrew" system out there (if anyone has links to more advanced stuff - such as on the order of homebrew sighting/retargeting systems like AirFiber's System - please post links!). Other links of interest:

http://www.alphalink.com.au/~derekw/upn tcvr.htm

http://www.hut.fi/Misc/Electronics/circu its/laserlink.html

http://www.geocities.com/Silic onValley/Lakes/7156/laser.htm

http://www.n1bug.ne t/tech/laser/laserfr.html

http://www.n1bug.net/te ch/laser/alc_wa6ejo.html

http://www.repairfaq.org /sam/lasersam.htm

http://www.qsl.net/w1vlf/techin fo/optical_transmitters.html

http://misty.com/peo ple/don/laserdon.html

So - these systems have problems (line of sight being the largest) - but all systems have problems. At least one company (AirFiber) is using similar tech to run a business for WAN layouts - so it should be possible for a homebrew solution to be worked out. Are we going to simply wait until 802.11x really gets "outlawed" before we do something? What kind of shit is that?

Oh - wait - this is /. - where apathy seems to almost be the rule when it comes to politics...