Slashdot Log In
Wanted - 45 Mile Wireless Broadband?
Posted by
Cliff
on Sun Oct 14, 2001 04:19 PM
from the when-that-'last-mile'-measures-a-lot-longer-than-you-think dept.
from the when-that-'last-mile'-measures-a-lot-longer-than-you-think dept.
Slashbaby asks: "I am a net admin for a school division that doesn't have broadband Internet. We are a rural school division, so we don't even have a provider in any of our towns. What I am looking for is a way to get highspeed Internet access into our division through either RF or microwave. There is a city about 45 miles away, (max. distance) that has ISP's that would be willing to sell us bandwidth if we can find a way to get it the 45 miles to the schools."
"What I am looking for is either companies or websites that deal with this kind of technology. I have no idea what to really look for, so any help ideas would be appreciated. Our budget for this project would be ~$125 000 CND ($80 000 USD).
We are currently using Direct PC satellite (which is NOT broadband) Unfortunately, they are dropping us in 2003...they are dropping service for rural communities in order to expand service for government funded projects."
This discussion has been archived.
No new comments can be posted.
Wanted - 45 Mile Wireless Broadband?
|
Log In/Create an Account
| Top
| 409 comments
(Spill at 50!) | Index Only
| Search Discussion
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
(1)
|
2
What about.. (Score:5, Funny)
802.11(b) (Score:5, Informative)
JKoebel
Re:802.11(b) (Score:4, Informative)
Re:802.11(b) (Score:4, Insightful)
Re:802.11(b) (Score:4, Insightful)
Fresnel Zone (Score:5, Interesting)
Depends on the frequency you're talking about... (Score:4, Informative)
Line of sight is not a good rule of thumb for RF propagation- for some things it's a good rule, for others it's only a good determinant of the maximum possible range.
RF is an interesting beast, one in which at one frequency, you're absorbed by the media, in another you're scattered by the same. Sometimes reflection comes into play and the signal bounces all over the place getting where you don't expect it. Sometimes the signal penetrates some media and goes further than you'd normally expect it to. Sometimes the signal hugs the earth and follows it's curvature to some extent (Which is where people get the thinking of line-of-site from- some signals bend some don't.).
Low frequency can be propagated through water and rock. High frequency can't. Low frequency propagates along the curvature of the earth. High frequency propagates along straight lines from the emitter source.
You already have the answer (Score:5, Insightful)
BTW, whats wrong with two way dish ?
Range Reality Check (Score:5, Interesting)
Field day (Score:5, Funny)
Or maybe not.
/Janne
Re:Field day (Score:5, Funny)
802.11b point-to-point (Score:5, Interesting)
Satellite (Score:4, Informative)
http://www.intellicom.net/kids.htm
A suggestion (Score:5, Informative)
45 miles is a pretty long haul for RF, given as other posters have remarked, the Fresnel zone, line of sight, and - from what I have been told -- the the curvature of the earth at those distances.
I administer a WWAN for my employer. We use Solectek [solectek.com] Skyway wireless Point to Point bridges/routers. These units operate at 11mbps in the 2.4Ghz spectrum. I like these units alot, they are well made (NEMA compliant) and perform very well (~20ms latency on my 90 mile roundtrip network). They do not use 802.11b due to some the inherent problems with that standard. Their WCOPP RF protocol is based on HDLC, and their bandwidth managment is top notch.
Their maximum rated distance is 30 miles. My longest link currently is 18 miles (line of sight) and works great. While you may not be able to dp 45 miles with one link, it might be possible to operate a repeater site off of some radio tower between you and the city. I have 2 such sites, due to line of site concerns.
Good luck!
Cringely did this w/802.11b & Directional Yagi (Score:4, Interesting)
The story's an interesting read [pbs.org].
Form a co-op (Score:5, Insightful)
Why doesn't the local communities get together and form a co-op? The school system would take the lead on this since they would benefit first but the rest of the members would benefit.
If your system is anything like where I grew up, we had small schools for each of the communities. Why not take a room from each of the schools and turn it into the local pop for the service. If you've got a line of sight from each of the schools or could get access to a point where you could relay it, then you wouldn't have to worry about using T1's to connect each of the locations.
The co-op would sell access to the Internet and since they're the only game in town there's no competition.
The school system would get deep discount since they're providing the space and power. But, setup a non-profit to run it and make them responsible.
Of course they'll be some interesting political hurdles to jump but hey that's what makes life so great.
If you live in Virginia there is a state program to get deep discounts called Virginia Link [valink.org]. They did have some really nice pricing on T1s and installation. James
Satellite? (Score:4, Informative)
I know that ping times are a little crappy, and if you want to do any hosting you'd best forget about it and all, but it's not too bad a solution.
Down here in Australia, we've got a real problem with rural schools. 45 miles is nothing, some face distances of hundereds of miles to the nearest populus. Telstra, our major carrier tend to pitch the satellite option to our rural users quite heavily.
I work for a regional school, and although we aren't far from a small population, we still don't have access to DSL or anything similar, so we use a Sat. connection. It isn't perfect, but it does the job where the kids are concerned. It serves 150 desktops without any real difficulty, and with very little downtime due to the satellite itself (some due to the people running it though).
I'm sure there must be some Sat. options available in other countries (after all our uplink is in the U.S.). You might want to give it a try!
My high school had a wireless broadband network. (Score:4, Insightful)
A little poking around on the net brought me to this site [packetworks.net] which explains all the details of the install at my school and the other schools in the board. You might want to check out that site for some ideas anyway.
Long shot 802.11 (Score:3, Informative)
- http://www.oreillynet.com/pub/a/wireless/2001/0
5 /0 3/longshot.html
It would be interesting to see if they could pull this off with repeater stations, the only problem being cost for putting up the antenas needed. Not sure how much that would cost, but I'm guessing a lot!multilink ppp (Score:5, Informative)
A school district that did something similar (Score:5, Informative)
From here [asba.ab.ca]:
Northern Lights School Division No. 69
Project brings the internet to rural school division
Northern Lights School Division defied conventional wisdom to bring the world to the desktop of over 6,700 students and 700 staff in 25 schools. Using Wi-LAN technology the jurisdiction established the world's biggest wireless education system in both geographical area (5,714 square miles) and number of sites. It cost them $650,000.
The project has been recognized for its innovation and successful implementation both within the educational community and the industry. ASBO International awarded project manager Gary Krawchuk the Pinnacle Award for Excellence, making him the first Canadian to receive this prestigious award.
For more information contact Ed Wittchen,
Superintendent, at 1.780.826.3145.
Two way Satellite (Score:3, Interesting)
I've been using a tachyon system for over a year and I find it works just fine for web surfing, email, FTP uploads, etc. May not be good for gaming, but students are supposed to be doing real work :)
Consider Frame Relay (Score:5, Informative)
We used Intermedia for our primary pipe, but for redundancy, we got a second pipe from Southwestern Bell Internet Services. 1.5mbps, 64 IP addresses, DNS provided by them if we wanted to use it (which we didn't). They used Williams for their upstream backbone, which performed rather decent. All for only about $500/month, again with no mileage or loop charges.
Most likely Pacific Bell and the former Ameritech have similar pricing since DBC has borged them both.
We've done 58 miles... (Score:5, Informative)
I am co-owner of a tech engineering company in the mid-west. We specialize in 4 areas, Cisco, Linux, Medical IT and last but not least wireless network design (LAN, WAN and Long Haul).
We had a customer that needed an interum solution (something to last them about 10 months until another means of connectivity came available). It had to be inexpensive, relatively fast, and wireless. We used FHSS gear to accomplish our task (Proxim RangeLAN2 to be exact). Our reasons were many, but I won't go in to that here. I will say forget about 802.11b for this (and for any serious wireless tasks other than LANs). We used two Proxim 7521-05 access points (the XR series as it outputs at 500mW as opposed to the 7520 which outputs at 100mW). As someone alluded to earlier, you have to have Fresnel clearence (ie cooperative geography). You have to know how to do a path survey, and you have to do one methodically at this kind of distance.
Let's assume that for you "task at hand" you can gain Fresnel Clearence and you want to do this. Since you are in Canada, you have to know your output power limitations, here in the US you cannot use high-gain antenna's with the 500mW AP's, unless you attenuate the signal before it reaches the antenna to reduce the output power to legal limits (and in the Carribean where we also do a lot of work, no one gives a rats butt what the law says). Not a problem for this type of thing, as normally the cable length from the ap to the Antenna on top of the tower is sufficient to reduce signal strength. Anyway, a couple of 21dBi or 23dBi parabolics, a couple of AP's (one in master mode, one in station mode), some cable and either your own tower or access to a tower on each end. Keep in mind, you can always use a repeater (passive or active) to clear obstacles in the middle, or to zig-zag as needed. Let's look at some dollar figures.
7521-05s normally retail for about $1,100 bucks. We are currently buying them for $189 from a place that bought out an ISP that went belley up. They are brand new in OEM packaging. Their address is www.imsales.com. So...
$400 for two APs
$800 for two good quality Parabolic Antenna'
$800 for excellent quality cable
$500 for two polyphaser lightening arrestors
Who knows for towers.
You got a long way to go before you reach 80 G's.
Now, the down sides. First, the speeds aren't going to be stupendous. You'll get between 800Kbps and 1Mbps. Still, not bad. The task of path surveying is not for the inexperienced. It requires lots-o-experience and knowhow, but there is certainly someone in your area that can do it (ask the local cell phone company who they use). Finally, antenna aiming is critical.
There are some other technologies that could get you higher speeds at a higher cost, but still unlicensed. Again, if you want to discuss this in more detail, e-mail me (rindeee@yahoo.com)
Anyway, I hope this helps. I will gladly give you more specifics, debate the virtues of various wireless technologies for this aplication, etc via e-mail at rindeee@yahoo.com. Be glad to help you accomplish your task...I think you will find it quite pleasing in the end.
PS. "Catagory 3" 802.11a (there are three classes of 802.11a the third intended for longer distance point to point) may be workable for this, but it's not on the market yet, so I don't know. The 2.4GHz stuff (Proxim RL2) is nice as the lower frequency than 802.11a (which runs at 5.8xGHz) is a bit more resiliant and has much better propegation over long distances.
For more info look at www.proxim.com and go from there.
Use your 'bird' (Score:3, Funny)
Enjoy!
I don't see why not! (Score:3, Informative)
Here are some URLs you might find interesting: HPWREN [ucsd.edu] (featured here recently) have a 45mb backbone using western multiplex tsunami [wmux.com] kit, and 802.11b [nocat.net] access points. They use solar power and batteries to power some backbone nodes.
Some other people using mostly 802.11b kit who will have some information you can use: BAWUG [bawug.org] PersonalTelco.net [personaltelco.net] NoCat.net [nocat.net] Freenetworks.org [freenetworks.org]
Using 802.11b or similar tech, you should expect each wireless hop to add about 5ms of latency, maybe a little more depending on distance. You can quite easily build a repeater by connecting two bridges together by a X-over cable. You could probably do this with Linksys WAP11 or similar, but over this type of distance you will find it much easier to use something like the high-spec version of Cisco Aironet 350 bridges [cisco.com] (the 100mW versions will push the signal a lot further - 25 miles with 24dBi antennas - you can use Cisco's own, alternatives include Superpass [superpass.com] (based in Waterloo), HyperLinkTech [hyperlinktech.com] and others.
Aironet bridges let you set the distance of the link which modifies timing parameters (a slight problem with standard 802.11b over long distances), and their security is better than WEP.
There's plenty of homebrew opportunities for antennas and other related kit, although I guess they're probably of more use to people who don't have a budget to play with (: There's a collection of links on this page [spacehopper.org] with a particular focus on homebrew kit.
45Mbit licensed or unlicensed gear (Score:4, Informative)
You will need a clear fresnel zone of around 300 feet (back of the envelope figures) above the tallest obstruction in the path. So you are probably talking about a 400+ foot tower, or something like a 150 foot tower on a 300 foot hillside (cheaper).
A 45 mile link will be hard to align properly, you will want to hire professionals. Cell phone companies use this kind of gear and go these distances regularly, for their cell-to-cell backhauls.
Um, why wireless? (Score:3, Informative)
45 miles is nothing when you expect to pay about $1000 per month for a full T1 over 250 miles. I'd guess you can get a fractional T or link to a frame cloud for about $500 per month and about $2000 per point. If your budget is $80,000, that leaves you with $70,000 (in one year) to pay for Internet services from an ISP. You should be able to get internet services for less than $1000 per month. If you're looking at $80,000-$4,000 (for hardware) = $76,000 / $1,500 (per month), you'll be able to have that active for over 50 months (that's over 4 years for those counting).
Skip the huge outlay of money for a technology that will be sketchy at best in bad weather and go for something that works and is proven many, many times over. If you want equipment recommendations, let me know. You can pick up some standard T1 routers (Cisco) with an integrated CSU/DSU off eBay for close to $1000 each. Your ISP may not even require you buy one at their end if they've got space on their T3...
All money estimated in U.S. currency.
Eric
Microwave is the way to go (Score:5, Informative)
This type of application can, I'm sure even in Canada, use licensed point-to-point microwave. This allows lots higher power than 802.11 (forget the "b" which means higher speeds for even shorter distances). Typical rule-of-thumb is that frequencies under 10 GHz can go up to 30 miles (okay, say 45 km) on a single hop, if you can get line of sight. The site in question might need a repeater along the way. The terrain is all-important.
It probably is possible to get some microwave radios on that budget, though a repeater would possibly blow the limit. Harris, for instance, has a good selection, and a free program, Starlink, on their web site, which does path calculations for various radio - antenna combinations. (You can source the radios elsewhere, but Starlink is obviously geared to match Harris' own radios.) These would probably deliver 3 to 45 Mbps, depending on the radio in question. Industry Canada (which regulates spectrum matters) would probably be able to point you in the right direction for licensing and frequency/path coordination.
-1, Troll? (Score:3, Informative)