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Wireless DATA Link
Gepeto_42 writes "Somebody asked me to help him find a way to get a data link from the coast to a little island where he's gonna have his business (I can't give too much details, it's still secret). The island is at about 10kms from the coast. Is there something else than HAM that could work? Micro-wave? It's in Quebec, Canada, by the way." Probably the best solution would be the 802.11 wireless LAN cards with a souped-up antenna - I'm pretty sure that people have made these work farther than 10km.
Take a look at http://www.cisco.com/warp/public/cc/pd/witc/ao340a p/prodlit/obrc_in.xls. The Cisco Aironet stuff can do this no problem, the spreadsheet above will give you the ranges, height requirements for earth curvature, and expected bandwidth based on the different types of antennas, as long as you can get line of site. I have done a few shots maxing out at about 15 miles using the parabolic dish antennas w/o a problem at 11 meg. Works great!
I haven't seen this mentioned earlier, possibly because the required frequency is used for something else in Canada...but try LMDS. It's line of sight, I think, but the range should be sufficient. Look here for more info. http://www.lmds.vt.edu/
Never let your fears overcome your dreams.
In most countries, you can't use amateur radio for commercial purposes.
As other posters have suggested, your best bet is a point-to-point microwave relay. Talk to a local communications engineer about cost, licensing, bit rate and link margins. There are many prepackaged digital microwave systems available today.
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the biggest problem with sending anything over long distances is packet latency. you can have unlimited bandwidth, but if you have high latency, your overall service level goes down.
anything that is satellite based will add quite a bit of latency (what i've heard is about 400ms each way).
802.11 is pretty much out of the question. it's slower than microwave, and has the distance problem. large signal amplifiers could probably make it work, but i doubt it would be very robust at that distance. 802.11 also decreases in overall bandwidth the more distance between nodes.
microwave technology can go about 30 miles, and has pretty low latency. you'll need some land on the mainland (rent tower space) to put a microwave dish, and another tower on your island (or whatever it is). i've setup and used one-way microwave connections, and they're suprisingly fast (i was about 15 miles from the tower). microwave is also good for cooking passing birds, but that's a different story.
if you'd like to read a little up on this technology, www.thebeam.com sells commercial and residental microwave packages. most of them include tv also. i don't work for them, i just admire their technology.
Why read the article when I can just make up a snap judgement?
if you need a low-cost solution, than there is only 802.11. everything else will cost you a multiple.
I've used 802.11 only for shorter distances, but have reports, that using (good) yagi and parabolic antennas is working for 15 km.
But you need a direct line of sight, with absolutly no abstacles. And keep the koax-cable to the antennas as short as possible!
Furthermore, most 802.11 equipment is available in an european and an american version. The american version has up to 5times more power.
bye, Adrian
"The Stratum 100 and Stratum 20 are point-to-point transparent MAC layer bridges which provide full duplex 100bT connections over links up to seven miles (11.2 km)."
"The Stratum MP is a multipoint learning bridge which provides half duplex 10bT connections to multiple facilities over links up to 12 miles under FCC rules, and over 5 km under ETSI rules."
I used to do some contract work for WaveSpan, the guys who developed these and got bought by Proxim.
Have you checked out infrared lasers? I've heard of people trying to link cities with lasers so it might be able to do that distance. The market is still very new...does anyone know how much that would cost?
Freewave DGVRO-19 frequency-hopping spread spectrum data transceivers. These devices operate over the 138-144 MHz frequency band, transmitting at 2 W. 20 mile range claimed to be line of site licensed. dunno how expensive they are.
This spec puts the range of a pair of 21 dbi dishes at 25 miles.
_ ___o1.htm#xtocid191346
http://www.precept.com/univercd/cc/td/doc/pcat/ao
Its on the internet so it must be true.
Microwave will definatly work over that distance.
You are however going to need a tower on both
sides. Its not gonng be cheap but I have seen ads
for 45 mbit microwave setups. 10km is not a distance you want to try to hack together with
things like 802.11B cards. If this is a buisness
then they should be buying commercial grade products.
I don't buy this bird-cooking stuff, at least not at the scale this fellow is talking about. Although I grant it might be possible for, say, commercial TV transmitters. Check out this link, for example:
http://www.wirelessmountain.com/superl inkspecs2.html
It's a 10baseT microwave link that will do 15 km with an output power of a whole 50 watts. My 1200 watt microwave might be sufficient to cook a very small bird in a minute, but 4% of that power isn't likely to do much.
A back-of-envelope calculation suggests that even if a small bird like a grashopper sparrow were to absorb 100% of the power of this beam and was perfectly insulated by its feathers, it would heat up by about 0.7 deg C per second. That's slow enough that it certainly won't cook a bird flying through the beam; the bird would somehow have to perch right in the beam and stubbonly stay there despite feeling uncomfortably hot. Oh, and when it passed out it would have to somehow stay in the beam to actually get to cooking temperatures.
And of course in real life, the bird won't absorb anything near 100% of the power, and would lose a lot of the gained heat to the air around it. So if the original querent sets up one of these microwave links, he should plan to keep getting his fried chicken the usual way.
"Try increasing the power for the antenna."
And, after IC finds out, and the RCMP breaks down your door and confiscates your equipment, tell them that the one armed man made you do it. =)
Note that, with the EIRP limits typical of radiated power regulation, even extra gain due solely to antenna modification is cause for concern.
well, sooner or later Cisco will cook up a CCNP or IE test for it then... ("Q1010: When attempting to establish an access-list on a 25xx router while under fire from customs...").
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You could use a commercial wireless data provider. If nothing else has coverage, some of the satellite networks should be there.
You could run a Aironet (Cisco now) wireless bridge. My guess is that this would cost about $5,000 (USD) for the 2 bridges and antennas. These things are sweet though. They're even a cost-effective alternative to a wired connection across town.
There's always microwave, with the licensing hassles and cost.
For the low-speed route, you can do something close to what hams use. A number of companies (like Paccomm http://www.paccomm.com) sell commercial (non-amateur) wireless data modems. You can hang a pair of these on a VHF or UHF frequency and do at least 2400 bps.
The most important piece of the puzzle was left off of this question. At what speed is the connectivity needed? Another question would be what level of reliablity.
First of all, let me qualify the following information with the fact that water changes things. A lot. Especially at frequencies up in the ghz, where water is essentially a mirror. That said, running a link across this much water isn't impossible, it just takes some engineering work.
The first piece of information I want to provide is that you can do a 2.4ghz 802.11b link at 11mhz over this distance with the right antenna system without even breaking a sweat. There is sufficient link margin for 99.99+% uptime. I have links running over 20 miles without any problems at all. You should also have almost no interference problems in the environment I envision. Again water will be an issue, but you should be able to work around that. This would provide a 11mb/s radio rate (About 5-8mb/s usable) link. This would be cheap. About $2000 an end when you get done putting together all the pieces. Towers not included.
Using different equipment, I can go up to 15 miles (24 km) at 93Mb/s. Assuming this is 10km or less, I can also go up to 7 miles (11km) at 420Mb/s (Full Duplex, 840mb/s aggregate). Of course these are much much much more expensive.
All of the above options are license-exempt, which basically means that at least in the US you don't need a license. I think that Canada is in the same boat, but I would have to do some more research. There are also licensed options.
To hopefully drive home the point above. You need to find someone qualified to do the engineering on this. It is NOT as easy as it looks. I find that most "experts" on this either are in the category of "I've done a couple of these and they work" or "I couldn't make them work". You need to find someone who understands the inner workings of why these work or don't. If they don't know about path loss calculations, freznel zones, etc. etc. etc. then they're probably not going to be any good to you.
I normally don't try to market my services when I post. However, if you can't find someone you feel is qualified or if you'd like me to look over someone elses design, drop me an email.
It appears that there is an issue here, but it's an 802.11 issue, not an IP issue as I'd assumed the poster was implying. See here for a subsequent SlashDot article by someone else talking about the need for less than 20usec latency in 802.11, which would be in the 1-2 mile range.
Just consider the power in your home microwave. It can cook birds easily if they stay there for a minute. Now think about how if it's going to be able transmit 10 km...
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Who said it would cook the bird just if it was just flying by anyhow? It'd have to sit there or something...
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3 miles is 4.8 KM, or 4800 Meters. :)
"Why do you consent to live in ignorance and fear?" - Bad Religion
I'm gathering that since he's going through all the trouble of having the business out on an island that far from shore, and keeping the nature of the business a secret, that security is a major concern. For this reason, you cannot rely on 802.11-based solutions or packet radio (also referred to above as HAM or amateur radio). Even WEP on the 802.11b standard is, IMHO, insufficient security, particularly since it is non-directional; any signal strong enough to get out to the island is also strong enough to cover an awful lot of land, and anyone in that area could sniff it. Packet radio is even less secure, and again, as noted above, there are probably restrictions on commercial use.
There are a multitude of systems for inter-building and inter-campus bridging, all of which will get you significant bandwidth. Some use microwave technologies, other use lasers. I'm not aware of how much curvature of the earth takes place over 10 KM, or how tall a tower you may be able to build to see over the horizon, but I would definitely look there. One more thing, also security-related: physically secure the land-side of your connection, as it's a perfect place to just hook up a laptop and sniff like the dickens.
For your security, this post has been encrypted with ROT-13, twice.
FWIW, if the range is 10 miles that page says you could expect 11 Mb/sec out of the Ciscos.
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According to an Airport Hacker Page... You can get around +- 3 miles (4800 KM). You might need to come up with your own hack. Try increasing the power for the antenna. Or you could try a PrimeStar Sat Dish. Problem is I don't know the range on these things and they are extreme directional sensitive.
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