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3.5 MILE WIRELESS BRIDGE

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Anonymous
a b F Wireless
August 27, 2005 7:46:29 AM

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Hello, I am trying to figure out how to make a bridge from my house to
a distant friend's house (about 3.5 miles straight line) The purpose of
this bridge would be so that I could subscribe to dsl at his house
which is right about where dsl service ends. I have direcway and I hate
it. Anyway our properties are roughly at the same height, my elevation
is about 1600, his is about 1560, and there is a valley between our
houses that dips to 1300. I am planning on putting a 19dbi directional
grid antenna on a 5' tripod on my roof to make it about 45' off the
ground and connect it to a WAP11 which would then hook to my server, on
his end I am going to put the same hook up on the side of a 75' silo
and hook it to the dsl modem. I haven't climbed up on the roof yet, but
I am sure that I have a clear line of sight.

The moral of my previous paragraph is, would it be possible to
construct this bridge and it actually work, and does anyone have any
ideas on any eaiser way to get this done? Also the WAP11's have two
antennas so would it be possible to hook the directional grid antenna
to one side to send the signal to my house and connect an omni or
something to the other to send the signal to his house, or would this
just slow it down by making it a point-multi point? Thanks

More about : mile wireless bridge

Anonymous
a b F Wireless
August 28, 2005 11:51:26 AM

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> Hello, I am trying to figure out how to make a bridge from my house to
> a distant friend's house (about 3.5 miles straight line) The purpose of
> this bridge would be so that I could subscribe to dsl at his house

http://www.nodomainname.co.uk/Equation/equation_broadba...

The only thing I would say is that WAP11 2.2's worked very badly for the
longer link, i'm guessing it's a timing thing but when replaced with
version 1 it all worked fine. Your mileage may vary and they might have
fixed it by now anyway.

> ideas on any eaiser way to get this done? Also the WAP11's have two
> antennas so would it be possible to hook the directional grid antenna
> to one side to send the signal to my house and connect an omni or
> something to the other to send the signal to his house, or would this

Do what? The two antennas are there for diversity reception. When you
use an external antenna, use just one and configure accordingly in the
config so that the chosen antenna is both send/receive.

David.
Anonymous
a b F Wireless
August 29, 2005 12:21:38 AM

Archived from groups: (More info?)

JACOBKENT@DIRECWAY.COM wrote:
> Hello, I am trying to figure out how to make a bridge from my house to
> a distant friend's house (about 3.5 miles straight line) The purpose of
> this bridge would be so that I could subscribe to dsl at his house
> which is right about where dsl service ends. I have direcway and I hate
> it. Anyway our properties are roughly at the same height, my elevation
> is about 1600, his is about 1560, and there is a valley between our
> houses that dips to 1300. I am planning on putting a 19dbi directional
> grid antenna on a 5' tripod on my roof to make it about 45' off the
> ground and connect it to a WAP11 which would then hook to my server, on
> his end I am going to put the same hook up on the side of a 75' silo
> and hook it to the dsl modem. I haven't climbed up on the roof yet, but
> I am sure that I have a clear line of sight.
>
> The moral of my previous paragraph is, would it be possible to
> construct this bridge and it actually work, and does anyone have any
> ideas on any eaiser way to get this done? Also the WAP11's have two
> antennas so would it be possible to hook the directional grid antenna
> to one side to send the signal to my house and connect an omni or
> something to the other to send the signal to his house, or would this
> just slow it down by making it a point-multi point? Thanks
>


http://www.wirelessnetworkproducts.com/index.asp?PageAc...

Found this...

Lorenzo
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Anonymous
a b F Wireless
August 29, 2005 12:21:39 AM

Archived from groups: (More info?)

On Sun, 28 Aug 2005 20:21:38 +0300, Lorenzo Sandini
<lorenzo.sandini@POISTA.uku.fi> wrote:


>http://www.wirelessnetworkproducts.com/index.asp?PageAc...

Apparently these guys use the D-Link 802.11g access points in a
bridging mode. Is bridging mode included with these access points
normally, or does the firmware inside need to be reprogrammed for
bridging mode? I've got an older DI-614+ but don't remember
seeing a bridging mode in its setup.
Anonymous
a b F Wireless
August 29, 2005 12:44:56 AM

Archived from groups: (More info?)

> Apparently these guys use the D-Link 802.11g access points in a
> bridging mode. Is bridging mode included with these access points
> normally, or does the firmware inside need to be reprogrammed for
> bridging mode? I've got an older DI-614+ but don't remember
> seeing a bridging mode in its setup.

Dunno you'd have to look but plenty of very cheap, e.g. sub $50 AP's
will do bridging mode.

David.
Anonymous
a b F Wireless
August 29, 2005 5:47:23 PM

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Rôgêr <abuse@your.isp.com> wrote in news:AbWdnYZTJu5XuozeRVn-
hA@pghconnect.com:

>
> Keep in mind when you've climbed to the top of something like a 75' silo
> and you hear some weird sounds, check to see if maybe your knees are
> making contact at irregular intervals.

I didn't quite get this statement.

DanS
Anonymous
a b F Wireless
August 30, 2005 1:09:01 AM

Archived from groups: (More info?)

On Mon, 29 Aug 2005 13:47:23 -0500, DanS
<t.h.i.s.n.t.h.a.t@a.d.e.l.p.h.i.a..n.e.t> wrote:

>Rôgêr <abuse@your.isp.com> wrote in news:AbWdnYZTJu5XuozeRVn-
>hA@pghconnect.com:
>
>>
>> Keep in mind when you've climbed to the top of something like a 75' silo
>> and you hear some weird sounds, check to see if maybe your knees are
>> making contact at irregular intervals.
>
>I didn't quite get this statement.
>
>DanS
He is talking about your knees knocking because of the height!
Anonymous
a b F Wireless
September 2, 2005 1:16:27 AM

Archived from groups: (More info?)

I have a similar setup between my office and home - approx 7/10th of a
mile.
However, direct line of sight is not accomplished due to quite a few
trees.
I am experiencing varying success with bandwidth speed. It seems to
vary from
125 to 900 kbps. Most often at the low end. Any thoughts on how to
stabilize speed at the 900 kbps high end?
I am transmitting a signal from my office, using a flat panel antenna
(Model FP19W 19 dbi gain 2150m-2700 mhz), to my house
At my house I have a similar flat panel antenna that flows to a bridge
that flows to a Linksys Workgroup Switch EZXS55W
Version 3 that flows to DLink Access Point DWL 2100AP.
In my Dell Inspiron 9200 laptop I have an internal Intel ProWirless LAN

2100 3A Mini PCI Adapter. When I use the internal wireless I seem to
consistantly generate bandwidth speeds of 140 to 150 Kbps. However,
when I disable the interenal wireless and plug in my son's Netgear 54
Mbps USB 2.0 wireless adapter it generates bandwidth speeds of
900+Kbps. Thinking that it was a problem with my internal wireless I
went out and bought the same Netgear wireless device my son was using.
When I fired it up it would generate speeds of 140Kbps.
Any thoughts or comments?????????????????????
March 5, 2006 12:14:46 PM

Your going to mount an antenna at 75'. Well either your going to put your bridge at the top of the silo and run ethernet down it to your switch or computer or your going to spend ALOT of money on thick coax. For that run LMR600. Haven't priced it in quite a while but once you factor in connectors and a lightening arrestor (this is not an option if you car about your hardware) then your looking into the hundreds of dollars. Now if you can put a nema box up there and run ethernet down then you should be all set. If you can do that then a 19dBi antenna is WAY overkill. For 3.5 miles you can use something with much lower gain and directed pattern.

You mentioned hookin up his end directly to the modem. Huh? This would be fine for you but how is he going to get his internet? You'd hook the modem to a switch, then to the bridge from there. Again preferably with etherenet to the mounted bridge.

You didn't say how long a transmission run will be from your antenna to the bridge. 10 to say 40 feet should be fine with LMR400 or Belden 9913. About a dollar a foot or so. Again, since you are mounting above roofline a lightening arrestor is not an option, it is essential. Problem here is that it adds two connectors to the run. Typically this is going to be N connectors. Not the easiest thing to crimp and if you don't do it correctly then well, yoru signal strength will be sh*t. I strongly recommend getting your transmission cable runs measured, then buying the cable already crimped. Lightening arrestors usually are near the antenna so they can be grounded properly. What your suggesting is certainly do-able. The chances of a first time novice doing themselves correctly...not so much.
July 11, 2006 3:44:11 AM

Quote:
> http://www.wirelessnetworkproducts.com/index.asp?PageAc...

>$600 for a 3 mile bridge for home use???!!

You can do it for less than $100


If that's the case I would be very interested in setting up something like this. Could you provide a few links to specific pieces that would be needed to make a point to point link like that for an affordable price. ie. antenna, cables, routers for each end.
I've seen people link to antenna sites in other posts but there are so many to choose from I wouldn't know which ones to order. The link I would like to help my cousin set up between his home and office is about 1 mile away. Thanks, for any help you could offer.
July 11, 2006 9:41:44 PM

See my post(s)

I don't really feel like going through the calculations, that sounds too much like work.

I think the record is 125miles with 8-10' dia satellite antennas. (I don't know if they used a power booster)

Blue68F100: I would not recommend adding a power amp to the system, overkill at best, and would invite unnecessary regulatory intervention.

As for cables from the bridge to the antenna, make them short, cat5e will be cheaper, signal will be better and can easily be run up to 100M (330 ft) Just a thought... If the distance is too long, then run fiber, by way of converters, then if lightning were to strike the hardware at the on other end of the fiber would have a chance of surviving.
July 15, 2006 4:06:38 PM

You guys are approaching this from the point of view of it being ONLY a hardware problem. This is an ignorant way of looking at it.

The wifi protocol is not designed to work at long distances. The reason is because the longer the distance introduces a higher transmission time. As the transmission time goes up packet collisions will increase.

Wireless communication ... you can think of every person sharing the same wire that goes to a switch/hub. And they are all trying to send out data to that switch/hub. Each time they send at the same time a collision occurs and the packet is lost. Wifi uses a number of collision avoidance and collision detection algorithms but they are only robust/effective/good when the transmission time is low. The more time it takes to send a packet the higher the chance for a packet collision. That is basically why wifi is not designed to be long distance.

----

bottom line is that you may be successful in overcoming the physical connection (antenna, signal booster, etc). But you will never have a great connection no matter how good the connection.
July 15, 2006 8:04:23 PM

Quote:

The wifi protocol is not designed to work at long distances. The reason is because the longer the distance introduces a higher transmission time. As the transmission time goes up packet collisions will increase.


Please back this up. Radio wave travel at about the speed of light, or 186,282.397 miles per second The time to travel 3.5 miles would be 3.5/C=1.9e-5 seconds or 0.019ms if your are thinking in terms of pings... Packet colisions would not be an issue.

And like I said before, there is a record on the books for a 125 mile wifi link. :wink: Link -note it was un-amplified!
July 16, 2006 4:04:33 AM

look i studied 802.11g protocol a while ago and these are just things i remembered off the top of my head. I don't have my textbook here and notes so I'm not gonna back up my claim with the specific equations that you use to determine throughput when you have specific Transmission-Time (Tx) and Receive-Time(Rx) .

Rx = (bits in a packet) / ( 54 Mbits/Sec )
Tx = Length of distance / c (speed of light in air)

All I know is that you have a ratio of: Tx / Rx

And as this ratio gets too high (Tx gets large in comparison to Rx) throughput goes down.

-----------

The actual hardware connection and signal degradation does not affects the theoretical throughput. The signal degradation affect how much noise is in the signal.

Wifi uses a form of Forward Error Correcting FEC called Turbo Coding. It has different tolerances of noise and once you reach a specific tolerance your packets are corrupted beyond correction. This causes packets to be lost and throughput goes down.

------------

So the moral of the story is that the longer the connection the lower the theoretical throughput.

As noise is entered into the equation the throughput is reduced by some multiplicative constant.

-------------

so i might say something like: theoretically it would have 10 Mbs (not based on anything). assuming no noise.

but then if you have noise you would have something lower than that.
July 16, 2006 2:04:42 PM

Thanks for the info. I just wanted to know what defined 'long distances' I know with satellite internet there are large latencies because the satellite is in geostationary orbit, at 22,240 miles. I don't remember what the bandwidth is.

Go with practical experience, links at 802.11b speeds have been made at distances much larger than 3.5 miles. I don't know if 11g is better or worse than 11b at range due to the protocols used.

By the equations you provided and assuming that the packet size is the same it would be worse due to the higher rate 54 vs 11 Mbit/sec. (I would say the higher rate would reduce the distance by about 11/54 or about 5:1)

Did they 'tweek' the transmit/recieve timing to maximize throughput for 125 mile record link. I read they were using linux and if they had open source drivers for the cards then it is possible.

I don't know what the original poster's DSL connection speed would be, but I am guessing it is much lower than the 11g speeds.

I worked through the link margins. For the transmit power and recieve sensitivies I fould, at 3.5 miles, 15dbi antenna's and short antenna cables the link should work at 54G speeds with no margin. The hardware will fallback to lower speeds if that is the case, large margins will be had a the lowest .11g speeds (min 6Mbit)
July 16, 2006 4:19:43 PM

for such long distances there are a number of specific settings you can change to affect the Tx/Rx ratio.

-one would be to limit the maximum packet size to be smaller by half or a quarter


--------
To avoid more collisions at long distance it would be smart to ALWAYS use CTS/RTS collision avoidance.

Essentially collision avoidance algorithms try to prevent collisions. In 802.11 when you send small packets collision avoidance is not used and you just try to transmit (knowing that there is a probability that it will collide with another transmitter). With larger packets the time it will be in the air is longer and the chance for collision increases. So it uses collision avoidance ... specifically it is called CTS/RTS collision avoidance.

For those of you who don't know what CTS/RTS is: RTS/CTS = Request to Send/Clear to Send .
1st the original-sender broadcasts to the access point (i.e. d-link router)
2nd the access point tells all listening unknowns to stop transmitting for the duration of time that the original-sender needs to send its message
3rd when the access point has finished with that it sends a CTS to the original sender.
4th the original sender transmits its large packet
5th all senders go back to regular sending

802.11 is deterministic. When normal transmissions occur (i.e. without CTS/RTS synchronization) there is a good chance it will be successful. But it is never 100% sure to get the packet through. This is because there are always numerous users trying to send always and they aren't usually being synchronized with the CTS/RTS schema.

-------
July 16, 2006 4:23:36 PM

ethernet is also deterministic. It only works when you have very small transmission time, Tx, in the network. Longer Tx times usually result in more collisions... and thus lower throughput.

This is why ethernet works well when you have short connections that are less than 100meters. As soon as you go past 100meteres... it starts to break down exponentially.

--------

gigabit ethernet is even more sensitive to Tx times... because it goes back to the ratio of Tx/Rx... since you have 1Gbs transmissions the Rx time:

Rx = (bits in a packet) / 1 (Gb / sec)

becomes really tiny. So to keep the ratio small that means you have to have even smaller ethernet connections. Probably less than 100meters.

--------
July 16, 2006 4:25:56 PM

Quote:
By the equations you provided and assuming that the packet size is the same it would be worse due to the higher rate 54 vs 11 Mbit/sec. (I would say the higher rate would reduce the distance by about 11/54 or about 5:1)


yes that is definately correct. the faster the transmitting the more sensitive to long distance Transmit Times.



Quote:
Did they 'tweek' the transmit/recieve timing to maximize throughput for 125 mile record link. I read they were using linux and if they had open source drivers for the cards then it is possible.


Yes they definately did. they obviously had intimate knowledge of what settings to change in the 802.11 algorithms. Mostly messing with packet size and how to use the CTS/RTS settings.[/quote]
July 22, 2006 6:17:41 PM

I forget where it was, but I saw some sites using homemade antennas, some with tin cans, others using old sattelite dishes (Primestar etc, any can be used) with the antenna where the sattelite reciever would go, they were getting insane ranges.
July 22, 2006 9:03:24 PM

Seattle wireless is a good place to start for tin can antenna's and such.
July 24, 2006 5:27:23 PM

This shouldn't be too hard, assuming you haven't already attempted it. About three years ago, I did a 2 mile link along a very straight stretch of highway with no planning, a Linksys AP and grid antennas. Not to mention the antennas were only an average of about 7-8' off the ground, so I'm sure the fresnel zone was shot to crap. I got the link up within minutes of driving to the other end of my test zone and had good throughput. I don't remember exactly what, but my signal was near 100%, I think I got like 2-3mbps using an 11b AP.

It sounds like you have ideal conditions. The one thing I'd suggest is taking a look at Senao's CB3 bridges. I recommend them all the time because they're awesome. 200mW, power over ethernet, bridge or AP modes, top of the scale tx/tx sensitivity. I had one on a 75' tower in my backyard a few years back, coupled with a 15db omni, I could see it up to 5 miles away with a directional antenna, provided I was at a tall enough spot to see over the trees.

By the way, here are some pics of my distance test for your amusement.
July 24, 2006 10:03:10 PM

Excellent, someone with 'real' experience posting.
June 12, 2009 11:20:17 PM

I am a Surveilance technician and we are always building something to transfer video further and faster. Well in doing so we decided to see what these bridges are all about and not believing the spec's decided we should get a set in the Lab and see what they can do.
First of all,Yes they will send your wireless network a few miles with ease. The only downfall is the bandwidth drops off big time when extending the connection. The set we purchased were $600.00 for everything needed including the lightning arrestors. I see they are alot cheaper these days so if you don't mind sharing a little width and speed with the miles between you then go ahead they work. We use 900 Mhz wireless alot. It is much faster and sends video at 15 fps with no problem. But I understand we are talking about the internet here so Oops!
Thanks!
June 20, 2009 1:02:11 AM

Quote:
Archived from groups: (More info?)

> http://www.wirelessnetworkproducts.com/index.asp?PageAc...

>$600 for a 3 mile bridge for home use???!!

You can do it for less than $100



I have just bought a 24dbi grid antenna i also bought a tp link 54 accsess point and i have a netgear router can anyone tell me how to configure this to make a wireless accsess to my laptop? thanks. will rocbottom70@hotmail.com
August 31, 2010 2:07:55 PM

How do you use an AP as a bridge? I have not found any that can use the wireless signal from a different one as the "ISP".

Thanks
August 31, 2010 2:11:00 PM

What is available for < $100.00? Or less, because this post is very old?

Thanks
September 19, 2010 3:10:40 AM

syn1kk said:
ethernet is also deterministic. It only works when you have very small transmission time, Tx, in the network. Longer Tx times usually result in more collisions... and thus lower throughput.

This is why ethernet works well when you have short connections that are less than 100meters. As soon as you go past 100meteres... it starts to break down exponentially.

--------

gigabit ethernet is even more sensitive to Tx times... because it goes back to the ratio of Tx/Rx... since you have 1Gbs transmissions the Rx time:

Rx = (bits in a packet) / 1 (Gb / sec)

becomes really tiny. So to keep the ratio small that means you have to have even smaller ethernet connections. Probably less than 100meters.

--------



Use Linksys WRT54G Routers running DD-WRT. Then you can change the ACK timing and all the other goodies that make long distance wifi possible.
September 30, 2010 1:35:05 AM

The cheapest way to get a link that is going to have some sustainability to it is going to be using ubiquity products. They are considered "Carrier Grade" and have a proprietary TDMA protocol to mitigate interference from other AP's on the same channel. Since you're only going to need around 3-6mbit at the most, I'd recommend using a Ubiquity Nanostation M5 at both ends. Light, comes with POE injector and has a range of about 11 miles PTP between 2 of them at reliable MCS-12 - 15. They are also MIMO devices, which helps if there is some unusual RF activity in the range selected. All devices can be either a AP, AP WDS, or Client / Client WDS. Configuration is straight forward, and they are high power transmitters.
Recommended configuration flying blind:
5mhz channel spacing, Enable AirMax, enable encryption, set to AP WDS / Client WDS, configure in the upper most channel (use Airview spectrum analyzer thats built in if you're up to it) and
Set transmit power to 23 DBM, aim em approximately straight at each other, and go for it.
These things have a fairly wide azimuth antenna, but at the distance specified, it will not be an issue. The devices range from 80 - 120 depending on where you get them.
Another cheaper option from the same company is the BulletM5HP -- Same concept, just NOT MIMO, and attaches to any antenna of your choosing.
Be sure when buying these things that you upgrade to 5.2, most all of them come shipped with it, but just in case.
They are also low latency, especially compared to say 2 linksys WAP11's. Typical ping times on mine is about 0.3 MS per link at 20mhz width, at 3 miles a pop, and 1.7 with a 31 mile link running 40mhz channel width. The higher the channel width the more latency and more interference. Stay away from the highly populated 2.4 b/g band for best results with a PTP link that is NOT going on a tower. Also, be considerate of others... there is likely a tower some where near by that is in the line of transmission of your equipment.. try and use Airview to find a dead channel, and then only use the required amount of transmit power to get -63 signal.. This is being nice since its the ISM band and its anyones game, but why screw with some one if you dont have to? Also when aiming be advised that on most antennas down tilt / uptilt is much more of a game changer than left / right, since the beamwidth is usually tighter.
Hope this is of use.
!