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Wireless Growth & Wireless Interference
windowpain writes "An article in Monday's Washington Post says "The explosive growth of the mobile phone industry has crowded and tangled the nation's airwaves to such an extent that wireless company signals are increasingly interfering with emergency radio frequencies used by police and firefighters, public safety agencies said." Wifi is not a problem, evidently. Understandable, given its short range."
if the FCC (or whoever) made reasonable specs and if everyone's following the specs how can this mess happen.
=> fire people at FCC or sue mobile companies.
"Wifi is not a problem, evidently. Understandable, given its short range." Yah, that and the fact that the public safety networks operate in the 700 and 800 Mhz bands, whereas 802.11a and b currently operate primarily at 2.4 Ghz.
I'm not surprised it's the Washington Post who is reporting on this. I live in Washington, DC as a consultant, and travel a lot to other cities. I have had cell phones with three carriers, and with all of them I've had much worse trouble here than in cities elsewhere, without exception. On one hand, we have some serious density of equipment here, but on the other hand there are zones where one knows one will lose their cell phone signal; the worst two zones are adjacent to the CIA's facility and the Pentagon, for example. This sort of thing can't be helping the matter.
For your security, this post has been encrypted with ROT-13, twice.
This problem has been around for some time in the hearing impaired community.
- If spectrum is reshuffled, could this be an opportunity for the wifi-friendly (but still evil) Powell to allocate more unlicensed spectrum?
- Alternately, does the emergence of the interference bogeyman in such a prominent publication imply a tough PR road for more free spectrum?
- Could this be an opportunity for the cell carriers operating in the 800MHz band to switch to different technologies, or roll out newer services?
- Could these sorts of problems be used to get some federal money thrown toward development of software radio? would multi-format devices help avoid this problem?
As the submitter mentions, these emergency bands don't appear to be abutting or affecting the 2.4GHz range, but I imagine these issues will be relevant as wifi expands and interference problems begin cropping up.Most of the WiFi I know of uses 2.4 Ghz band (I know there are others out there though) And there doesn't seem to be a whole hell of a lot of it out there yet. Maybe it will one day be a bigger problem as it's deployment picks up. I'm looking forward to the seeded frequency hopping options rolling out in the long term, which won't cause very many people problems (at least for more than a fraction of a second) The frequency hopping method also adds the 'security by obscurity' slant to the signal as well -- if you don't have the seed and the algorithm by which the frequency is determined, you may have trouble sniffing out the data on the signal. All really neat stuff. I don't see the wireless stuff, at least the internet variety, as being all that useful, (pardon me all of you blackberry junkies) I think wifi has the solution to it all, conceivably (someday) even cellular could just use some of that bandwidth. It's just a matter of changing the infrastructure -- something that seems to take forever with folks like Verizon involved.
Speak for yourself.
As organized, the spectrum, which is a limited resource, simply can't accommodate everyone...
There are several wireless companies operating in the 800 megahertz band...
How finely split can the spectrum be before there's danger of overlap? Is it possible for, say, one phone to send signals at 800.0001 MHz while another does so at 800.0002 MHz? Where is the precision cutoff for neighboring frequencies before things start to interfere?
The coolest voice ever.
*Laughs at /. editor as he types this over a 6.1mile 802.11b link*
Really... the main reason for the interference between cell and emergency is that they are all moving into the same spectrum space. 800mhz is a busy place these days.
True wireless (802.11a,b,g) are all in FAR different spectrums so other than cordless phones and some radar equipment interference is a moot point.
Telcos have alot of dark fibre in the States. Most people assume that's optical fibre...but it's actually moral fibre.
802.11a and b currently operate primarily at 2.4 Ghz.
Actually, only 802.11b operates at 2.4 GHz. 802.11a operates at 5 GHz.
The emerging 802.11g standard is intended to deliver the same data rate as 802.11a but on the 2.4-GHz band.
The coolest voice ever.
Seems like we need to point the FCC towards Open Spectrum (mentioned in a previous Slashdot article). After all, why go to all the trouble of reshuffling the tiny spectrum we've got now when the proper devices and management can give us more bandwidth than we know what to do with yet?
How To Get Humans To Mars
I do some home and small business tech support in New York, and I've seen some interesting things happen with Wi-Fi.
The most interesting being the fact that I found 20 open and join-able networks on the corner of 20th and Broadway last week. I'd say some people need a lesson in security...
Also, I've seen people name their network things like "get the fuck off my shit" when neighbors try to join their network.
I'll also be interested to see if Wi-Fi networks effect piracy at all- what if the RIAA manages to crack down on piracy to a point that it cripples internet file trading (it wont happen, but come with me on this for a sec) and the only safe way to trade files is by sharing them on a local AirPort network. Then people can run around with their Wi-Fi PDAs with 1GB or greater flash cards, and download stuff from open networks they find on the street.
> Meantime, Fisher said many colleagues on the Anne Arundel County police force have found their own solution: They carry cell phones in case their radios go dead.
...)
so that being an option, why not have the cell companies take over administration of all the systems in these ranges, subcontracted thru local government offices? have the companies then manage (and be liable for) the need for non-overlapping frequencies separating critical traffic from the general public. especially the ones that shouldn't be driving and yapping on a cell phone as they hurtle through traffic (you know who you are!!!)
and yes, i know this puts a consumer-driven entity in charge of systems that are depended upon by lcoal/stage/regional entities, but hasn't private enterprise often proven its ability to manage complex systems a tad better than the government? could be a re-birth of telecom spending and contracts (which could mean jobs, more bottom-line investing, more attention on the nation's eroding infrastructure
when it rains, it gets real soggy. when it pours, i'm under the tap just _waiting_ for the joy
I thought one of the reasons the FCC exists is to allocate frequency blocks precisely to avoid problems like this? Aren't wireless devices supposed to be certified by the FCC?
Wifi is not a problem, evidently. Understandable, given its short range.
:-)
Ummm, no. Here's a frequency chart of the radio spectrum. People seem to think everyone uses all frequencies and it's one big radio spectrum blob. Radio spectrum resembles IP space, except in this case you can't create more of it. Print out the chart on a big plotter, hang it on the wall and impress your techie friends, and consult it when a wireless article is posted on Slashdot.
K3NG
Tired of being "punished" by the Slashdot $rtbl since 2002. I'm now over at http://soylentnews.org/ .
I would've thought emergency services always had some backup mechanisms in place to get back to the station in case of emergency.
Heck, I even thought the dash-cam that police cars are all supposed to have also relayed video back to a surveillance team back at HQ. Apparently it is not so. With risky, unpredictable work like emergency services at hand, I for one, am surprised they thought of fallback procedures only now.
I know transmitting live video from the surveillance cams is difficult, and multiple backup contact mechanisms would be expensive (cellphones, satellite phones et al), but then, I thought these guys would be the ones who deserve it most of all.
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
Is it possible that the FCC benefits from the artificial scarcity that its own policies impose on frequencies? There exist technologies to make much more efficient use of frequencies and to eliminate all interference, but mysteriously we still get all our services squashed into a small and crowded space where the right to broadcast commands high fees and prestige for the authorizing body (=FCC).
Ceci n'est pas une signature
Apart from a (very few) 3G phone users, we're all on GSM 900 or 1800 MHz. I understand there are two or three different mobile technologies in the US; does this use more spectrum?
When I am king, you will be first against the wall.
I've found a crapload of stuff around Union Square but haven't gotten up to 20th yet. I did notice that it was virtually a barren wasteland up near Times Square, but have found a ton of ESSIDs in and around the Village.
It looks like companies don't use 802.11 hardly at all, rather, the more residential a neighborhood, the more prolific the access points become.
Unfortunately there's virtually nothing near the Staten Island Ferry (I live in SI) other than that damn Starbucks that closes too early and the Verizon Wireless AP that's WEPped and closed. 802.11 in the Whitehall Ferry Terminal!
+++ATH0
The basic argument, like the article makes for first responders, is that the military band for communications is being encroached upon by civilian use. Having fewer frequencies directly impacts the military's ability to conduct training operations and exercises.
The Navy (Department of Defense) has a page which educates visitors and range spectrum users on how to defend against civilian encroachment of DoD frequency spectrum.
The Electromagnetic Spectrum Training Chart shows military uses of certain frequencies and the competing civilian use.
Still Mud? Try www.phoenixmud.org!
There is only so much frequency space, and once it's been allocated, no one wants to give it up.
Do you really think that amateur radio operators will come forward and say "Hey, we've got bandspace to spare, take some of ours!"?
Maybe there should be more stringent standards on how much interference an appliance creates?
But personally I say we just eliminate the CB frequencies. Only those with too much spare time and no mobile phone use it anyways. Let it go and get FRS or GMRS for pete's sake!
Hard loop..... huh?
Dynamic Designs
I really don't know about that. Just as receivers have tolerances, transmitters do too. So if I have a crappy transmitter and I tell it to broadcast at a certain frequency, there will be a certain tolerance there, unless I'm using a laser. They're certainly not. Even with a good transmitter, there's a certain +/- to the frequency distribution, although presumably less.
So ultimately, his question was quite a fair one - for someone to tell the difference between two signals 800.0000001 and 800.0000002, the two transmitters will have to be good enough to send out precise, narrow signals, and his receiver will have to be good enough to tell the difference.
-Looking for a job as a materials chemist or multivariat
It sounds like most of the problem is local agencies not monitoring the QOS of their radio systems. Most organization get a contractor to install the equipment, towers and contract for basic maintainence and then expect the system to run for years with little oversight..
Cell providers (and most commercial radio operators) know that the precise interrelationships are always changing. New buildings, new transmitters, malicious/accidental interference. Most wireless carriers send drivers with GPS/inertial locators and signal strength meters wandering about their coverage areas to locate areas of poor coverage. "..hear me now, Good!"
A friend once showed a map drawn by a wireless system installer showing that with X number of towers the entire coverage area would have maximum signal strength. Most government entities would stop here, believing the installer. But this wireless company did a standard mapping of signal strengths and found inadequate coverage all over, the number of towers had to be almost doubled from the original estimate and dead spots still exist.
Good radio operation is more than just getting a license and standing up a tower. Whining that the FCC should step in just becuase you're too lazy to fix you own stuff is irresponsible.
To preface my comments, I am a holder of a First Class Radiotelephone FCC license, and an active Amateur Radio Operator. I have been involved in communications of all types, from TV and FM transmitters to engineering two-way radio installations. Now with that said --
What a load of crap! It's not the problem of the wireless providers, it's a problem of coverage due to poor system engineering.
Most, if not all, 800 mhz emergency service systems operate on what is call a "Trunking System". What this is, essentially, a system of linked towers that communicate with the vehicle or officer on the street, then relay from tower to tower ultimately connecting to either the dispatcher or another officer. These systems are designed to be interoperable with each service, such as police, fire, ambulance, etc, so a single dispatch facility can communicate with everyone, and all services can communicate with each other.
To work effectively, you must have sufficient towers properly placed to assure that there is no dead zones. Given the expense involved in site purchase, permits, tower erection, equipment installation, and backup generators, the bare minimum is pretty much the rule. Plus, you cannot physically survey the entire area of coverage, you use topo charts to try to make sure your engineering is sound.
To blame the wireless providers is silly and stupid. Modern 800 mhz equipment is very selective, most newer systems operate via spread spectrum digital, and the chances of interference are minimum.
Additionally, emergency services have priority so if there is a provable case of direct intererence, the wireless provider must take steps to either stop the interfering signal, or cease operations entirely.
The amount of bandwidth basically depends on you much noise there is around- you can pack much more data into a narrow channel if the channel has hardly any noise, whereas if the channel is very noise you'll need a wide channel to send the same data.
Also in practice you need a gap between neighbouring channels- the receivers need to filter out the other channels and they don't do this perfectly (although the better the receivers are, the closer you can pack them in.)
However Shannons law only deals with broadcast communications where everyone can 'hear' everyone else equally, if you use directional antennas then it doesn't necessarily apply- two communications could use the very same channels.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"How funny that this should come up. I was just in a meeting last week talking about this very thing.
I am the Assistant Chief of a volunteer department north of Tampa, Florida. We operate off of the 800mhz radio system, and for all of the money we spent on it, you would think it would work better. Instead, we have spots where we can hear but not transmit, or just plain not get reception at all.
While we were talking about this one of the Hillsborough County chiefs brought up the fact that when he is at headquarters (where our central towers and dispatch are) he can't use his little car-alarm-door-unlock-gadget-thingy unless he is almost touching his vehicle. When he is at home, he can activate it from 200-300 yards away.
We have always blamed it on the hardware and crappy company, but now I think I might have to look a little more into what other kinds of interference would cause transmission and reception problems in the areas where we are having difficuly.
Random Musings
I'm a ham radio operator and I can speak first hand of this type of interference. Hams and Police/Fire/Emergency all use similar bands. 140Mhz 440Mhz The problem is when you get near and area with a high concentraton of cell phone towers you hear tons of digital interference. It's gotten to the point, where I live, that I dont' even turn on my radio when I'm in downtown. There are supposed to be filters around which can block out this interference but they are expensive and I've never met anyone that owned one.
There is an interesting whitepaper by people from MIT and harvard here http://cyber.law.harvard.edu/ltac98/whitepaper.doc
This brings out the need for changing spectrum regulations from auctions to open spectrum access for three specific reasons:
Technical: The system of allocating a particular frequency band to a single user is based on outdated technology. Early receivers and transmission schemes were such that we needed to be concerned about the possibility of interference. The development and implementation of spread spectrum and digital radio technology allow us to use receivers and transmission schemes such that interference is not a significant concern.
Economic: An auction acts as barrier to entry to small firms and unproven technologies, which are often the sites of innovation.
Constitutional/Legal: By allocating spectrum licenses, the government is essentially picking who can talk and who cannot.
It would be interesting to see if the technical reasons stand the test of these problems of interference. On another note: With so much electromagnetic transmissions, I wonder if the health hazards are being evaluated and addressed systematically and strategically.
Interference is a relatively new part of this problem. For decades, public safety has had "holes" in coverage caused by hilly terrain blocking the signals. Same thing happens with cell phones, but the cell phone companies can afford many more transmitter sites to fill in the gaps. Put another way, public safety coverage will never be as good as cell phone coverage, for reasons that have nothing to do with interference. Reallocate the spectrum all you want -- it won't cure this problem, but it could help with the newer interference issue. What might also help is independent third-party review of public safety radio system designs that are originally drawn up by the same companies that are selling radio systems to the public safety agencies. Some agencies have no idea of what they ordered or what performance to expect or, moreover, the tradeoffs between cost and performance.
I posted this story a bit ago, but it's relevant yet again. A while ago I added the Home Media option to my Tivo. It connects to my Linux box via 802.11b. So I'm streaming an MP3 from my linux box one day to my tivo->stereo and the Mrs. puts something in the microwave. The music stops. The microwave counts down, 3...2...1 and the music starts. Very cool. Clearly the microwave has been interfering for years with my web connection, but the latency and design of the web allow for intermittent connections and thus I don't normally realize the microwave is killing my connection. But you sure do when an MP3 cuts out. Very cool.