Point to Point using a pair of Access Points ?

Hi All,

I wish to link two PCs together using 802.11b. Sites are about 1/2
mile apart.

Both locations will need antennas to be 10ft above building height to
be able to see each other. I plan to attach the antennas to guyed 10ft
masts.

I would like to run power + CAT5 to water tight boxes at the top of
each 10ft mast. This will keep coax length to a minimum.

At one end, I can easily put a low cost Access Point.

What should be at the other ? Another AP is the obvious choice, but is
it possible to set up peer-to-peer using low cost APs ?

Any other options or thoughts ?

Thanks, Mark.

"Mark Aren" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) m...
> Hi All,
>
> I wish to link two PCs together using 802.11b. Sites are about 1/2
> mile apart.
>
> Both locations will need antennas to be 10ft above building height to
> be able to see each other. I plan to attach the antennas to guyed 10ft
> masts.
>
> I would like to run power + CAT5 to water tight boxes at the top of
> each 10ft mast. This will keep coax length to a minimum.
>
> At one end, I can easily put a low cost Access Point.
>
> What should be at the other ? Another AP is the obvious choice, but is
> it possible to set up peer-to-peer using low cost APs ?
>
Two true access points cannot connect directly to each other. However, some
vendors sell "access point" products which can be configured by proprietary
means as bridges (instead of as access points).

That confusion aside, the best device for what you descibe is a wireless
Ethernet bridge. Two such products for 802.11b are the Linksys WET11 and
the ZyXEL B-420. The remote PC would still need an ordinary Ethernet NIC;
you could also insert a switch for multiple PCs.

(E-Mail Removed) (Mark Aren) wrote:

>I wish to link two PCs together using 802.11b. Sites are about 1/2
>mile apart.
>
>Both locations will need antennas to be 10ft above building height to
>be able to see each other. I plan to attach the antennas to guyed 10ft
>masts.
>
>I would like to run power + CAT5 to water tight boxes at the top of
>each 10ft mast. This will keep coax length to a minimum.
>

You can avoind running a separate power lead up the mast if you use hardware
that is POE compliant. This standard allows the use of used wires in a typical
Cat 5 bundle for power.

The difference in signal loss for 6" of coax and 2' of coax is not that great.
You may wish to consider mounting the AP at the base of the pole to reduce wind
loading/swaying.


>At one end, I can easily put a low cost Access Point.
>
>What should be at the other ? Another AP is the obvious choice, but is
>it possible to set up peer-to-peer using low cost APs ?


A router in bridging mode at one end and an AP in bridging mode at the other
should do the trick. The price difference for consumer APs and Routers is almost
nil.

What you really need to look into is the type of antenna needed.
Start with http://www.ecommwireless.com/calculations.html and pay particular
attention to the Simple Wireless Network Link Analysis and Fresnel Zone
Calculator links.

Clark et. al, thanks.

For reply:

"A router in bridging mode at one end and an AP in bridging mode at
the other should do the trick. The price difference for consumer APs
and Routers is almost nil"

From my question:

"I wish to link two PCs together using 802.11b. Sites are about 1/2
mile apart.
Both locations will need antennas to be 10ft above building height to
be able to see each other. I plan to attach the antennas to guyed 10ft
masts. I would like to run power + CAT5 to water tight boxes at the
top of each 10ft mast. This will keep coax length to a minimum. At one
end, I can easily put a low cost Access Point. What should be at the
other ? Another AP is the obvious choice, but is it possible to set up
peer-to-peer using low cost APs ?"

I guess my next question is about real equipment models. I have a
DI-614+ which I thought was an Access Point until because it has a
DHCP server, supports serveral clients and has built in NAT as well as
a WAP port. I then spotted the words "wireless router" on the front of
the unit.

Can anyone recomend Dlink model numbers of gear for each end of this
link please. One AP and one Wireless Router.

I guess there is a conflict between Marketing departments at Network
companies and techies who write wireless FAQs (from what I have been
reading) in terms of equipment descriptions.

Thanks,

Mark.

(E-Mail Removed) (Mark Aren) wrote:

>I guess my next question is about real equipment models. I have a
>DI-614+ which I thought was an Access Point until because it has a
>DHCP server, supports serveral clients and has built in NAT as well as
>a WAP port. I then spotted the words "wireless router" on the front of
>the unit.
>
>Can anyone recomend Dlink model numbers of gear for each end of this
>link please. One AP and one Wireless Router.


I agree - it's confusing as all get out. Dlink calls your 614+ a wireless
router. I'm in the middle of setting up a similar system and have not figured
everything out yet. But, based on what I've managed to learn, I think you have
half of what you need already.

According to the Dlink web site (www.dlink.com), your DI-614+ should work well
with a DWL-810+ Ethernet to Wireless Bridge ($61 at buy.com). This will plug
directly into one computer, or into a switch which can in turn support multiple
devices.

Since you are trying to span about 2700', you are going to have to do better
than the rubber duckie antennas on each box. Electrocomm has a great web site
with some calculators that are essential. Go to

http://www.ecommwireless.com/calculations.html

and click on the first link: Simple Wireless Network Link Analysis. The default
frequency and RF power output values are OK. The cable is not - you should
select LMR-400 or lower. 400 is best - but runs around $1 per foot. Lower
numbers equal higher loss, but thinner coax is easier to work with.The default
BER is not right either. Figure on -65dBm as more realistic. The longer the
cable run run, the more loss. Your antenna cable probably shouldn't exceed 25',
or you'll need to go to a much larger antenna, or use really expensive cable.

What this will tell you is that you are going to need directional antennas with
16dBm of gain or better at each end to get a solid connection. The key result
from the calculation above is Thermal Fade Margin. You want at least 20dBm.

You have lots of choices for antennas, and they aren't that expensive. (Dlinks
are, but you don't need to buy their brand.) Designs to look at are Yagi, Vagi
and parabolic. These range in cost from $30 - $60 each. I've found both of these
companies to be extremely helpful and reasonably priced.

http://www.aerialix.com/
http://www.fab-corp.com/

Another bit of trickieness is figuring out the right connectors for all the
cables, especially if you put in a properly grounded lightning arrestor, which
you need to if you are mounting outdoors.

(E-Mail Removed) (Mark Aren) wrote in
news:(E-Mail Removed) m:

> I would like to run power + CAT5 to water tight boxes at the top
> of each 10ft mast. This will keep coax length to a minimum.

good

> At one end, I can easily put a low cost Access Point.
>
> What should be at the other ? Another AP is the obvious choice,
> but is it possible to set up peer-to-peer using low cost APs ?

you can use AP-APC configuration, or bridge both ends (cisco
"bridge" is actually AP-APC, what a liars they are)

> Any other options or thoughts ?

survey the air, maybe theres no room for more radio there

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You may never know -- UNTIL IT'S TOO LATE.