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New Member

AP/BR 350 distance limits and "bridge spacing"?

A Cisco-related consultant warned me that the AP 350 has

a "distance limit" of about 1 mile. However, I found

anecdotal reports from other users who were reaching out

(at least) almost four miles. How far will they go, and

what performance aspects degrade over distance?

Is the AP 350 a good idea for a WISP, assuming I want to

reach out about five miles? (Using three central APs on a

tower with 12 dB 120-degree sectors).

I wanted to use AIR-WGB352R workgroup bridges in some

remote sites, but I also wanted to stay 802.11b / WiFi

compatible. But I'm getting the impression the WGB's

must talk to a Cisco AP, and that AP won't be in a WiFi mode.

The consultant said I should be using bridges instead

at my central site, in an AP mode. (Sadly, I bought three

WGB352 thinking they had an AP mode, but it's only the

BR350 that does that.)

The Aironet 350 Series Wireless Bridge (AIR-BR350) has a

Radio menu setting called "Bridge Spacing" from 0 to 40

kilometers. The manual says "The Bridge Spacing setting adjusts

the bridge's timeout values to account for the time required

for radio signals to travel from bridge to bridge."

All this made me wonder how the remote radios get their

configuration for "bridge spacing", which made me think

again that all this isn't 802.11b compatible - that it's

Cisco proprietary. Do I have that right?

4 REPLIES
New Member

Re: AP/BR 350 distance limits and "bridge spacing"?

.11b spec says AP to client distance max is 1 mile - going further depends on your client devices and signal strength, and probably means less than "11Mbps".

You would only use an AP as a WISP base if the users were mobile and close by. WGBs are client devices, jsut like PCMCIA cards, so they only talk to APs and that is 802.11b spec/compatible.

Bridge-to-bridge is where you leave the standard behind. The bridge spacing setting helps set the timing to correctly deal with the distance between the bridges.

Matthew Wheeler

Blue Modal

New Member

Re: AP/BR 350 distance limits and "bridge spacing"?

There is a timing issue in the 802.11b (which is the AP mode for a Cisco radio). You should not be able to reach over 1 mile, but everyone seems to be able to get longer distances. I have reached over 5 miles without problems. Just remember, you can push the MHz on your home PC... eventually you will have problems. Personally, I do not think you would have problems with 5 miles.

You too got miss informed by the Cisco documentation on the WGB. I wish Cisco would be more straight foward. Just a note: THE 340 bridge DOES NOT work with the 350 bridge (it is pretty tough to find that in the Ciso documentation, but Cisco TAC will let you know). I have successfully got a 352 workgroup bridge to work with a 342 bridge in access point mode.

I am not sure why they told you to use bridges at the central site in the acess point mode. This would only be useful if the bridge (acting as an acess point) was going to repeat to another bridge.

The bridge spacing is to allow for that timing issue I talked about earlier on the 802.11b. The other bridges in the system all sync to the setting of the Root radio.

Mike Wrobel

Bridges Communciation, LLC

mikewrobel@bridgescommunications.net">mikewrobel@bridgescommunications.net

New Member

Re: AP/BR 350 distance limits and "bridge spacing"?

What kind of setup (antenna, cable, amplifier, etc.) are you using to expand the AP range to over 5 miles? I have a 342 bridge in AP mode at my base station, and I tried to get a 352 workgroup bridge to associate to it at about 3.5 miles. It will associate, then immediately drop giving "max radio retries" errors every few seconds. The link bounces up and down. The signal strength/quality looks good for the few seconds that it is up, but more "max radio retries" errors and it goes down.

Gregg

New Member

Re: AP/BR 350 distance limits and "bridge spacing"?

Gregg,

I use grid antennas, low loss LMR-600 cable and power amplifiers as necessary (this is unlicensed and the power amps must stay within FCC specs for EIRP). The first thing I learned is to get antennas and cable from someone other than Cisco. Great radios, but the antennas and cable are made for the layman on simple building to building installs, not long range or long waveguide run installs.

Did you check the frequency spectrum at both ends to make sure no one else was in your way? Are you using good directional antennas? What is your wave guide length (at each end)?

Mike Wrobel

Bridges Communications, LLC

mikewrobel@bridgescommunications.net

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