Long Distance Wireless Internet

I have a customer who wants to use his exsisting T1 at his main
building and provide wireless connectivity to his secondary building.
This secondary building is approxiametely 200 yards away and has around
80% clear line of sight.

My question is what equipment is neccessary to handle this situation
and what options do I have.

Thank You

On 14 Nov 2006 12:03:42 -0800, "BlackJackal" <(E-Mail Removed)>
wrote in <(E-Mail Removed). com>:

>I have a customer who wants to use his exsisting T1 at his main
>building and provide wireless connectivity to his secondary building.
>This secondary building is approxiametely 200 yards away and has around
>80% clear line of sight.
>
>My question is what equipment is neccessary to handle this situation
>and what options do I have.

What exactly do you mean by "80% clear line of sight"? That 20% may or
may not be a big deal.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

BlackJackal wrote:
> I have a customer who wants to use his exsisting T1 at his main
> building and provide wireless connectivity to his secondary building.
> This secondary building is approxiametely 200 yards away and has around
> 80% clear line of sight.
>
> My question is what equipment is neccessary to handle this situation
> and what options do I have.


Try a Linksys WRT54G and WAP54G (in client mode). If that doesn't work,
go with some commercial gear and higher gain antennas.

"BlackJackal" <(E-Mail Removed)> hath wroth:

>I have a customer who wants to use his exsisting T1 at his main
>building and provide wireless connectivity to his secondary building.
>This secondary building is approxiametely 200 yards away and has around
>80% clear line of sight.

You don't have line of sight. At 2.4GHz, you need MORE than optical
line of sight. You need to clear the Fresnel zone. See:
http://www.terabeam.com/support/calc...esnel-zone.php
for calcs and explanations. If there's any garbage within 80% of the
Fresnel Zone, you will have signal loss and variations as thing move
around.

You might want to measure the distance instead of ballpark guessing.
At about 600ft, you'll need some outdoor antennas. See the FAQ at:
http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations
for how to do the link and antenna size calculations. With junk in
the Fresnel zone, I would just add some extra antenna gain to take
care of any fades. Instead of a 20dB fade margin, try about 30dB
instead. Ask if you need help.

>My question is what equipment is neccessary to handle this situation
>and what options do I have.

I'll assume you want to transparently bridge the two networks so that
they look like one big network. You need a "transparent wireless
bridge" or just plain "wireless bridge". These are two identical
wireless bridges the simply glue your two networks together. However,
you need to disclose the number of MAC addresses at each site that
will need to be bridged. Most of the cheapo, bottom of the line
wireless devices have some real limits on the number of MAC addresses
they will pass.

We also need to know what speed you're expecting. I suspect that
sharing the T1 (1.544Mbits/sec) is not the only purpose of this link.
My guess(tm) is that there will also be some connections between PC's,
printers, and servers at the two locations. 1.5Mbits/sec isn't fast
enough for that. What speed thruput were expecting for the link?

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
> "BlackJackal" <(E-Mail Removed)> hath wroth:
>
> >I have a customer who wants to use his exsisting T1 at his main
> >building and provide wireless connectivity to his secondary building.
> >This secondary building is approxiametely 200 yards away and has around
> >80% clear line of sight.
>
> You don't have line of sight. At 2.4GHz, you need MORE than optical
> line of sight. You need to clear the Fresnel zone. See:
> http://www.terabeam.com/support/calc...esnel-zone.php
> for calcs and explanations. If there's any garbage within 80% of the
> Fresnel Zone, you will have signal loss and variations as thing move
> around.

<snip>

Maintaining a fresnel zone as computed on this website seems darn near
impossible in most situations. Is this independent of polarization?

What frequency range is valid for this website?

(E-Mail Removed) hath wroth:

>Maintaining a fresnel zone as computed on this website seems darn near
>impossible in most situations. Is this independent of polarization?

It's mostly independent of polarization. By mostly, I mean that there
are some differences. The effect of encroaching on the Fresnel Zone
is that the object creates edge diffraction, which redirects the
signal out of the line connecting the RF source and receiver. The
degree of edge diffraction is polarization sensitive, where horizontal
object tend to diffract a verically polarized signal more than
horizontal. However, the effect is not huge and for initial
calculations, it should be considered polarization independent.

It's NOT impossible for most situations. For example, at a range of
300ft (the alleged maximum range of conventional wireless), the 80%
Fresnel Zone radius is only 4.4 ft. That's easily achievable.

Where it gets difficult is for long range links. For example, at 5
miles, the midspan clearance should be 42 ft. In effect, that means
that both antennas at the link ends must be at least 42 ft off the
ground level or the ground will end up inside the 80% Fresnel Zone.
Actually, it's somewhat higher than 42 ft because of the curvature of
the earth. Also note that this is only at the midpoint of the link.
As you get closer to each end, the required clearance becomes less.

>What frequency range is valid for this website?

The Fresnel Zone varies with the inverse square of the frequency:
Midpoint clearance in ft = 72.1 * sqrt(D/4f)
D = distance in miles.
f = frequency in GHz.
It breaks down at extremely low frequencies due to the inability to
find a sufficiently large clearance area. At the high end, it starts
to involve optical effects (fringing, scatter, speckle, interference
patterns, etc) at about 22GHz. I would guess(tm) that the simple
approximation is valid from about 500MHz to 22GHz. It's also a far
field calculation that will break down for short distances which
involve near field calculations.

This online calculator seems a bit more useful for calculating
required clearance for various objects along the path:
| http://www.ratrivertech.ca/archives/...Calculator.htm


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
> (E-Mail Removed) hath wroth:
>
> >Maintaining a fresnel zone as computed on this website seems darn near
> >impossible in most situations. Is this independent of polarization?
>
> It's mostly independent of polarization. By mostly, I mean that there
> are some differences. The effect of encroaching on the Fresnel Zone
> is that the object creates edge diffraction, which redirects the
> signal out of the line connecting the RF source and receiver. The
> degree of edge diffraction is polarization sensitive, where horizontal
> object tend to diffract a verically polarized signal more than
> horizontal. However, the effect is not huge and for initial
> calculations, it should be considered polarization independent.
>
> It's NOT impossible for most situations. For example, at a range of
> 300ft (the alleged maximum range of conventional wireless), the 80%
> Fresnel Zone radius is only 4.4 ft. That's easily achievable.
>
> Where it gets difficult is for long range links. For example, at 5
> miles, the midspan clearance should be 42 ft. In effect, that means
> that both antennas at the link ends must be at least 42 ft off the
> ground level or the ground will end up inside the 80% Fresnel Zone.
> Actually, it's somewhat higher than 42 ft because of the curvature of
> the earth. Also note that this is only at the midpoint of the link.
> As you get closer to each end, the required clearance becomes less.
>
> >What frequency range is valid for this website?
>
> The Fresnel Zone varies with the inverse square of the frequency:
> Midpoint clearance in ft = 72.1 * sqrt(D/4f)
> D = distance in miles.
> f = frequency in GHz.
> It breaks down at extremely low frequencies due to the inability to
> find a sufficiently large clearance area. At the high end, it starts
> to involve optical effects (fringing, scatter, speckle, interference
> patterns, etc) at about 22GHz. I would guess(tm) that the simple
> approximation is valid from about 500MHz to 22GHz. It's also a far
> field calculation that will break down for short distances which
> involve near field calculations.
>
> This online calculator seems a bit more useful for calculating
> required clearance for various objects along the path:
> | http://www.ratrivertech.ca/archives/...Calculator.htm
>
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

I guess the effects of the fresnel zone are not very significant on
simple NFM. I plugged in 440Mhz and came to the conclusion that simplex
ham radio was impossible unless I and the persom I am communicating
with take human growth hormone.

When I have run Splat!, the lower frequencies had better propagation
due to diffraction. That is, radio waves exceed line of sight.

(E-Mail Removed) hath wroth:

>I guess the effects of the fresnel zone are not very significant on
>simple NFM. I plugged in 440Mhz and came to the conclusion that simplex
>ham radio was impossible unless I and the persom I am communicating
>with take human growth hormone.

Apple and oranges. Actually, Fresnel Zone diffraction is very
signifigant at proportionately longer ranges on VHF/UHF. The
difference is that you can yack away on NBFM VHF/UHF with perhaps a
0dB SNR (signal to noise ratio). Try that with data communications
running at megabit rates and nothing will work. High speed data
requires more bandwidth and a much better SNR. Much of the common
obstructions are fairly transparent at VHF/UHF and opaque at 2.4GHz.
Lower frequencies have less path loss. Lots of other differnces
making comparisons rather awkward. If you're dealing with long range
VHF/UHF links, you most certainly will be dealing with the Fresnel
Zone.

>When I have run Splat!, the lower frequencies had better propagation
>due to diffraction. That is, radio waves exceed line of sight.

Yep. The radio horizon is well beyond the optical horizon. Put
crudely, lower frequencies bend more easily. The ultimate form of
bending is at the old Loran frequencies (about 100KHz) where the space
between the ionosphere and the ground form two sides of a waveguide.
You could go around the world several times without bouncing or
diffraction.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558