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An anonymous reader writes "A 72-mile link was installed last month from San Diego to San Clemente Island, using standard 802.11b WLAN gear and high-gain, 2-foot parabolic antennas. More in this Computerworld article."
I'm waiting here stuck with v90 :/
War surfing!!!
Lovely. Now there is a path 72 miles long for people to exploit. Insecure networks, always fun...
Does this mean I have to wear a 2 foot antenna on my shoulder when I which to connect my laptop to the internet? This all sounds so incredible.
So now you can surf the internet from almost anywhere on their network!! *yay*
/* oops I accidentally made a comment, sorry */
so how did they overcome the earth horizon limitations?
Watson: Did you get it?
Bell: Yes, send more porn.
"Smokey, this isn't Nam, there are rules." -Walter
That would be good for my parents' house which is more than 5 miles from the nearest excahnge, but is in an ideal location for that antenna - at the top of a hill. I hope this becomes available to the masses at a reasonable price soon.
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"The test was declared a resounding success when the message '@#FGGgWEe#GR... +++ATZ +++ATH0 NO CARRIER' was successfully received by the San Celemente station. Congratulations to all involved!"
how would you warchalk this link? I mean, besides the technical difficulties of writing on water. Do you put a really REALLY large ear on the ground near the antenna? In all seriousness, this is quite an impressive feat, especially using a highly crowded spectrum. I am curious though how it handles atmospheric interference. Over 72 miles the beam width on this thing must be miniscule and I would think any atmospheric disturbance would send the link crashing. Then again, I've never passed 802.11b traffic more than 2 or 3 miles.
Great read, but somehow I picture something like this mounted on a 40' mast.
--
The link to San Clemente Island -- used to carry data from a seismograph, data logger and Global Positioning System receiver....
During an earthquake, will that data registered by the seismograph still make it to the mainland?
More importantly; if it's a REALLY big one, will the GPS record San Clemente's new position?
Problems with telecommunications in CALIFORNIA!
Long distance on water...
All this troubles because the 1 watt limit...
Can you say Linksys Wan products sold by your local ISP for shareing a 128 bit isdn connection will be a huge hit for those mid sized mom and pop gas chains running linux POS systems.
a beowulf counter strike server!!
Seriously, however, broadcast medium networks like 802.11b are best used for distribution, not long distance point-to-point links (fiber is ultimately cheaper on a bit-for-bit basis), but this demonstrates that you can build a really cheap 802.11b distribtuion network to solve the Last Mile Problem. Another nail in the coffin of Ma Bell...
...-.-
can bring it down! Imagine, if you will, that there's a Quickie Mart in the middle of this stretch. Every time the microwave oven heats a "Pocket", the link is down.
Too late for the Richard M. Nixon comeback! If only this technology existed in 1972...
Eve Fairbanks says I drive a hybrid!LOL
before a Corona commercial shows the guy on the beach adjusting the dish and using it as a shade umbrella?
I have always been under the impression that for part 15 devices that the power is given in mv/m.
According to http://www.radioinnovation.com/Howto/how_pass.htm the maxiumum power for a part 15 device in the 2.4ghz range is allowed an average power density of 50 mV/m at a range of 3 meters, and is a transmitter power of -3.4 dBm when used with a perfect 1/2 wave dipole. -3.4dBm is, http://www.qsl.net/vk6zse/wattsdbm.htm, between 500-800 microwatts.
Now I realize that they are using parabolic antennas, but are they still meeting that average power density, I suspect that ERP is likely greater than 1 watt when using directional antennas.
Then the LA afternoon smog rolled in cause 98% packet loss. Reports of low flying sea gulls being singed as they passed through the deadly rays have also been reported.
Amateur radio operators have been doing stuff like this for years on frequencies above and below 2 Ghz. Here's a listing of distance records .
Tired of being "punished" by the Slashdot $rtbl since 2002. I'm now over at http://soylentnews.org/ .
They must have used a huge pringles can.
If you can't beat them, arrange to have them beaten. -George Carlin
And in other news, Wernher von Braun established a 200 mile hop from Baltic Coast to London using a high bandwidth high latency connection.
Which is probably why they shot over water. No trees, shorter towers. It's great to see this stuff getting tested, especially by educators who tend to publish their results. Hams have been enjoying this sort of fun for a long time now, and the basic problems are still in front of you. You have to have line of site (plus some extra height for the Fresnel effect), and you still have to buy and point dishes and since 1 watt WAPs aren't sitting on the shelf, you still have to get a pair of expensive little amplifiers. These things can at least be purchased now, and if you want to set up such a link, attend your local Amateur Radio shindig and you'll find piles of retired microwave enthusiasts, eager for the chance to lend a hand....
I just heard some sad news on talk radio - video game character Mario Mario a.k.a. "Super Mario", was found dead in his NOA home this morning. There weren't any more details. I'm sure everyone in the Slashdot community will miss him - even if you didn't enjoy his video games, there's no denying his contributions to popular culture. Truly an American icon.
In the article, they say the purpose of the link is to carry data from a seismograph, data logger and Global Positioning System receiver. Does this mean that their connection drops when there is an earth quake or tremor?
The parabolic dish is directional. I would assume that its direction changes during a quake.
Alien visitors picking up the signal have warchalked the area just outside of San Diego. Aerial observers have taken a photo of this this.
(b) The maximum peak output power of the transmitter shall not exceed 1 Watt. If transmitting antennas of directional gain greater than 6 dBi are used, the power shall be reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi.
I am just guessing at what they mean in the article by "high-gain". They say they are using a 1 watt bi-directional amp. My personal definition of high gain is a lot higher than 6dBi.
Am I misinterpreting this?
Eve Fairbanks says I drive a hybrid!LOL
1 watt + 2ft dish at 2.4ghz would put a useable signal into a satellite in geosync orbit. 72 miles seems modest as far as range goes... the gain with a good 2ft dish at 2.4ghz is pretty extreme. If it is line-of-sight at 72 miles the signal should be way way above the noise.
A few people have questioned the towers necessary for this as well as have mentioned amplifiers. In San Diego, the hill at Pt. Loma has a large antenna tower on it. Perfect. San Clemente Island is no slouch on the altitude either. Another thing to take into consideration is that San Clemente Island is a military installation. The entire island is owned by the US Government. I wonder just how much they are respecting the 1 watt limit on 802.11b considering that the signal beam would be so small that interference would be nill.
I want a house along the signal path so I can enjoy roast $BIRD as they fall onto my picnic table.
Trolling is a art,
Wow. Only 70 comments and the site's kacked and died. Is this a new record?
"No problem. I have the capacity to do infinite work so long as you don't mind that my quality approaches zero."-Dilbert
here's a link to more information via HPWREN's web page: hpwren San Clemente
Frank Dwyer (dwyer@sdsc.edu)
Assistant Director, IT Services
San Diego Supercomputer Center
Not smog, specifically. A place I used to work at had a microwave connection on the roof, feeding from one of the taller skyscrapers downtown. On days when it snowed, or rained really hard, the net connection would flake out like crazy.
'Snow Days' took on a whole new meaning.
Tangent: a bigger problem was the various punks and squeegee kids 'playing' in the microwave field. They would jump back and forth in front of the dish for the little zap it gave you. We tried to warn them....
ZAP 'Owww! My sperm!' ZAP 'Funny, it didn't hurt the second time... '
If Jesus wants me it knows where to find me.
People are going to be able to surf while surfing. Now someone just needs to invent a waterproof laptop.
~S
probably. I am only guessing but when they say "runs with the maximum 1-watt power output allowed by the Federal Communications Commission for 2.4-GHz equipment" I assume they don't mean 1W power out of the bridge, but rather 1W effective. So assuming 24Dbi antenna's (the highest gain parabolics I have seen for 2.4Ghz) the should be ok with 100mW bridge units which is probably what they are using. I did not see them mention amp's anywhere in the article.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
(i) Systems operating in the 2400-2483.5 MHz band that are used exclusively for fixed, point-to-point operations may employ transmitting antennas with directional gain greater than 6 dBi provided the maximum peak output power of the intentional radiator is reduced by 1 dB for every 3 dB that the directional gain of the antenna exceeds 6 dBi.
Fab-corp sells a 24 dBi parabolic. If my math is right, that allows you 18 dBi of gain.
'SBEMAIL!' is better than a goat!!
San Diego sporting goods stores are reporting record sales of 12 ga. shotguns to San Clemente SDSC personnel who were alleged to have made cryptic statements about "frame drops", "bandwidth", and "all these f*cking seagulls".
Had seen a chart elsewhere (was really wanting to link to that) that showed the max somewhere around the 18 dBi you mention. Sorry fro tagging up the wrong language from the reg.
Back to the real point, 1 Watt bi-directional amp + "high-gain" directional does not take much to get into violation territory. Since they left out the gain of the antenna all we can do is guess, but 2' parabolics should get you into max gain without the amp.
Unless... [just dawning on me] the amps are only for receiving, i.e., NOT bi-directional! Now THAT would work without violation, just like some of the fancer wardriving rigs. It increases all the noise but the signal is still there to pick the digital bits out of.
Eve Fairbanks says I drive a hybrid!LOL
My math's a little rusty, but with a parabolic transmitter, they should have very little spread over the distance.
Which means that to exploit along the 72-mile path, you'd have to be at the right height to intercept. That's probably close to sea level at the midpoint (draw a line between the tips of a cat's ears for an illustration), but any bobbing in the waves will probably lose your signal.
Design for Use, not Construction!
OK that was a little confusing ;)
Let me try to clarify your example. If you're using a 24dBi dish, your gain is 18dB above the 6dBi level. You must reduce your power by 1dB for every 3dB of gain above 6dBi, so for your 24dBi dish you must reduce your power 6 dB (18dB/3=6dB) to 0.25W. (1/4 of the original 1W).
So, if the article is correct (and i doubt it is, you know reporters...), then they are probably violating the law.
Dude. Ginger was a beeyotch!
Now Maryann, THERE's a real woman for me! Mmmmmmm got that innocent midwest girly smile and those perky breasteses.....ACK!
igottagoseeyal8er!
Great. I'm going to get cracking on war-crop-circling. It's important to let our Martain neighbors know about potential free anonymous access points.
I've done 64 miles personally. I also know of a guy on the "big island" in Hawaii doing 84 miles (IIRC). We will be doing some links down in the US Virgin Islands in a couple of months (once it gets real cold here in Missouri ;) ).
ER
and since the Oronico card used in this setup is 15dBi intentional radiation per their spec sheet they have 3dBi to play with. The other thing you have to be carefull is bringing the sideband power down so that you are not tramping on adjacent spectrum (eg outside the 2.4Ghz ISM band, they really don't care how much you trounce on other 11b channels as it is an unliscensed application). I know Cisco's bridge has a 20dBi intentional output for the 350 series and they have a certified bundle using a 21dBi dish antenna for a combined power of 41dBi vs 39dBi for this setup. This is the longest shot we've heard of but in theory you could do even longer ones with our setup =)
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
We always had problems with an 8 mile link, I can only imagine how unreliable this link is over 72 miles. Amazing how many people have their own networks that interfere also. Its a pain to maintain those links. We switched to T1's to get more reliability (and more speed)
Sadly this is not going to be very useful in general.
Why?
Think it through - this will need to have a discreet dish at each end of the link.
Fine at your house, put it on the roof or a better positioned pole.
But at the Exchange end you will need one for every link. Now if you have 200 customers needing this can you imagine the physical mounting problem at the Exchange.
So in the end it will help (maybe) at the fringes of the phone network where physically connecting is not cost effective or practical (Scottish Highlands in the UK, Outback in Australia etc) but its not going to be available for the masses.
Now I have had a wireless telephone system here in the UK (Ionica - any of the other 64,000 users out there - most of us seemed to be techs?) But that used a low power direction dish at my end, and a much higher power single wideangle array at the exchange end.
"A 72-mile link was installed last month from San Diego to San Clemente Island, using standard 802.11b WLAN gear and high-gain, 2-foot parabolic antennas."
:)
I'm glad that my 15 foot satellite dish in my back yard is still good for something...
The race isn't always to the swift... but that's the way to bet!
Is the equipment water proof?
..
Even so, if the GPS or WAN antenna is submerged . .
I would guess that of more interest to the seismologists is the record of the information preceding the quake.
It's this that they are monitoring looking for signs of stress and movement to try and predict sesmic events, and use the seismic data for other science.
If the event is local enough to disrupt the link, then you have to fix it, same as if it brought down the poles for normal cable links.
Also don't assume every seismograph is in an active area[1] as we have plenty of the instruments over here in the UK and we're not exactly known for our 'big ones'.
We had a 10second ~4 in the Midlands the other month that was big enough to wake me up and go "WTF?" - but that was our biggest in 10 years.
Of real interest are the traces of distant seismic events and thier echos because analysis of the traces from several global stations can reveal a lot about the internal structure of the Earth, as the various types of seismic waves travel/refract/reflect differently in different mediums. Correlate enough and you can measure density of the rock and magma, and place the interfaces fairly accurately.
And your last comment made me spew coffee on the keyboard - thanks!!
[1] Sorry my US geography ain't the best, for all I know San Clemente Island could be volcanic, which would somewhat ruin my argument
"I rarely see mountains and trees sailing the high seas."
Just wait till the BIG one hits California.
an 18.5 minute gap in all transmissions from San Clemente...
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Cronus
Big freaking deal. Every week someone puts up an 802.11 link. Just throw more power and bigger antenna, and thats it.
Why is this news-worthy at all?...
Who cares.
Modesty is one of life's greatest attributes
This link is illegial. The FCC doesn't just limit the transmitter power (1w) for ISM2.4, they also have a limit on EIRP (transmit + gain). (the actual regulation is a bit overly complicated, it gives you a maximum EIRP of 9watts for a p2p link, or 4ish watts for a P2MP link).
They don't say how much gain their antenna has, but I have some 802.11b grid parabolics that are a bit under 2ft across.. They have 23db gain. That would have an EIRP of 203watts.. so far above the legal limit it's not even funny.
Is there anyway to use seperate transmitting and recving antennas? You could use a big honking dish for the recving and a much smaller one for transmitting?
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
A perfectly fed 2ft. diamater dish at 2.4 GHz has a gain of 24db, but even a Pringles can feed will give you a dish with 21db of gain. More importanly, the spatial extent of the signal will be minimized, allowing for cellular reuse.
Personally, at 2.4 GHz I'd go with a loop Yagi-Uda array instead, as they're still cheap, and much more wind resistant, something you care about when pointing matters. Make enough of them and they'll be as cheap or cheaper than the Yagis used for UHF TV reception.
Bottom line: There's nothing inherently expensive about gain antennas, and they're the cheapest way to improve the link equation.
...-.-
Theoretically, yes, but not sure how practical it would be, since the tranciever has only one external antenna input. I suppose you could use a splitter and diode setup of some sort (really guessing here) to have 2 antennas with one only transmitting and the other only receiving.
Does not look like what they did, they are using 40" mesh antennas, there is a link direct to the project site in another thread.
Eve Fairbanks says I drive a hybrid!LOL
in areas that experience significant rainfall and rainy season storms?
We have had a system running for more then 3 years from the summit of Mt Washington, to the North Conway valley in NH. No worries about freznel zone, as the 6000+ foot mountain works as a fine tower.
Somewhat unique in this case though is that we have winds that exceed 75 MPH more then 30% of the time. Try figuring out how to build an antenna and mounting system that remains accurate and doesn't blow away into Maine under those conditions!
There are several pics in the photo gallery of the summit dish. Here are several:
You may also find the weather stats of this location interesting.
Karma hammered. *ouch*
the 802.11b link was interesting but I want to know more about there 10mile+ 45mb 802.11a links.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
How the hell do they aim a highly directional signal like that?
I mean you can get your location pretty easily with GPS -- do they just do some basic navigational math, use a compass and then fine-tune?
Incidentally, is that also how they aim a directional antenna on a 25' post on top of a tower? Figure out the elevation for each point, set the inclination on the antennas and then hoist them on top of the tower and rotate the post until they find the signal?
They could probably extend the record alittle by putting a receiver on the Shuttle or the ISS
I realize the horizon problem has already been addressed -- but one other issue with sending low power long-haul signals over water is that of a ship crossing through the path.
The article says the total cost was about $3,000. There's no way they built towers high enough to overcome that problem on that budget. They're either in for some long nights troubleshooting when the signal disappears for a few seconds every now and then, or they just don't care.
-- People who hate Windows use Linux. People who love UNIX use BSD.
there is a way of doing a double antenna on a singnal input. I have a friend that has an antenna for satalite comunications (2m up and 440 down).
What he did was is has a boom with 2 directinal antenna on it that are perendiculare to each other.
Using this antenna (if he points it at an sat.) he can make it with 5w.
That dosen't explain why, YOU SUCK.
Yes, but there you're using a duplexor because they're on seperate bands. On the same band, you'd have the problem that your transmitter's radiation might loop back into the receiver. Less so on a directional antenna, yes, but just the same...
only if you happen to be in the very narrow linear path
High power, long range links deny service to other users of the spectrum. That's why they require licensing and use a licensed spectrum allocation. If you need a long range microwave link, get licensed! Don't hog a shared resource.
well there is the 5 mile link but and say 200 customers well set up a network to use the service tou get 2 or 3 antennas at your house. now you have a second distubbition point and a larger network. think of the posabilities :-P
It's amazing how many people you could be friends with if only they'd make the first approach.
Given that dishes are usually even cheaper than linear arrays, your "guesstimate" is off by an order of magnitude!
...-.-
Why does everybody type 'line of site' when it really is 'line of sight'?
Websight.
--- Hindsight is 20/20, but walking backwards is not the answer.
Any idea what the ping time is for this connection?
The pictures on the HPWREN website show that this link was made using 24 db grid antennas use with an 1 watt amplifier. This makes them outside the legal limits by far.
Seeing that, there's nothing special to this link, just a combination of off the shelf hardware.
They don't know...
Sadly I expect the practical issues of having your house festooned with other peoples dishes, and the normal paranoia over 'radiation' we see over phone masts, and the fact your link would be dependant on there not being a power outage at you neighbours up the road, and who exactly pays for the electricity for those other dishes.
Yes I think what you suggest could work well in sparse communities where people are used to being more self-sufficient and looking out for each other.
I just don't think its a practical thing in a dense population, there are better solutions for that.
There's apparently not many slashdot posters that have actually tried working with 802.11. It's horribly unreliable. We've tried going about 200 yards using NetGear Prism 2.5 based cards, and it simply does not work. After we added +15 dB gain dishes from fab-corp.com, it had a signal to noise ratio of about 10 dB. Pings were on the order of 2.5 milliseconds (nice!), but they increased to about 300 milliseconds and 40% packetloss when you started using the bandwidth. I've also worked with a local group of ISP's (we met at the ISP Forum in Atlanta about four years ago), and we've all tried 802.11 wireless and given-up on its use other than for very short range (like down the hallway) usage. 72 miles? I'd call it a hoax even if they said it was 7.2 miles.
What about probogation delaywhich is inherent in the 802.11b standard and the Inter frame spacing?
According to standard each station must be able to hear a packet being transmitted within the timing of a single 'SlotTime'. The default 'SlotTime' is 20 uSec.
So I don't see how it is possible to acheive such distances under the standard defined time slot.
Also what about RTS and CTS response, don't they need to happen within a SIFS interval. Calculating the propogation delay for a distance of 72 miles,this seems impossible.
any comments?
Depends on the equipment. Some cards have a connector for a second "receive only" antenna, and can (in most cases) be configured to use them for the purpose you're after. These cards aren't cheap though, so expect to pay a bit more for them.
Cards that support this sort of thing are usually noted as being capable of "Diversity", which is used mainly for noise cancellation in reflective environments, but could be used for a send/receive antenna scheme. You would want to separate your antennas by a big margin though, to avoid any sort of interference. Separation by something that reduces 2.4 Ghz signals would be best.
If you are restricted to a given ERP, you would not be able to increase the field strength at the receiver by using a smaller antenna and more power; all you would do is cover more area with your signal (and create more potential for interference). Plus, you have the expense of TWO antennas... it makes much more sense to use a bigger dish and reduce transmit power to remain legal, because you can squeeze a lot more out of the spectrum that way. (Sometimes the rules actually do make some sense.)
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