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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."
"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.
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.> 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
It's a combination of frequency, bandwidth, and a few other factors. For example, when something is at 800mhz, that's the center frequency. It will have a bandwidth associated that may be a few khz or a few mhz, depending on the application.
Then you get a combination of different technologies. Someone else mentioned TDMA, CDMA, GSM, and some others. Some of these operate in the same bandwidth without significant interference because the way they operate is so different. CDMA for example, doesn't suffer from the same kind of interference that TDMA, GSM and a few others do.
There's a technology called Ultra Wide Band that may take off over the next decade. While it covers a very large bandwidth (as the name would imply) that would normally interfere with other technologies, because of the way it operates, there's little, if any interference. The nice thing about it is, you can operate a number of different devices, each paid of sender and receivers has a "code" that allows them to communicate. Nothing else will interfere and many devices with different codes can operate in proximity.
Most technologies operate on the basic principal of sending a signal via the actual radio wave. They do this by modulating some part of the wave, usually frequency or amplitude (hence FM and AM radio).
UWB doesn't do that. Instead, it sends pulses very quickly (in picosecond lengths) and the pattern created by the pulses (think binary, on and off), are what are used to create teh signal.
Another advantage of UWB is that it works at a lower power (given the same range). Also, unlike the higher frequency applicatons (particularly when you get up to 5+ ghz), it doesn't have the same issues penetrating walls and such. Nice technology. Hope it makes headway.
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.