Airplane777
join:2004-06-20
| 2 APs near each other hinder operation ?
Anyone know if there is any study done on whether two APs operating near each other can cause detrimental operation to each other?
For instance in higher power transmitters, I have seen where one high power transmitter on a nearby channel, will "desense" a nearby receiver (receiving on a channel near the transmmit channel of the other unit), making that receiver incapable of receiving weak signals, that it might be able to receive if the nearby transmittrer wasn't turned on.
I thought that one APs transmitter might overload the receive section of the other AP, since the antennas are located so close to each other. This happens many times to regular two way transmitters if they are close to each other and not filtered well. And I don't think APs have much rf filter circuitry, if any in them. That would make them larger and cost more.
However since they are so low in power, maybe detrimental operation isn't a factor.
But I thought maybe other tech people here may know. |
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redpanther
join:2001-01-07
Hot Springs National Park, AR
 ·AT&T Southwest
 ·Cablelynx
| From my Amateur Radio experiences yes, a receiver can be desensed by near transmitters. However, if you are using such low power levels as these aps transmit and as long as the channels don't overlap seems likely you'd have no problem.
Just for reference though I am running 3 aps in wds mode all on ch 11 and see no problems in recieve sensitivity. |
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jimg_comp
join:2004-02-03 | reply to Airplane777
I have two Linksys wireless G routers stacked on top of each other both on different sub nets. The key I believe is to just make sure they are on different channels. In my tests, I get the same signal strength from both when roaming around. |
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Airplane777
join:2004-06-20
1 edit | reply to redpanther
Hi redpanther:
Thank you for your help and info.
I was thinking of mounting two antennas 2 feet apart on a pole with the two APs below. One AP is 500 mW and the other is 200 mW. The ants will be at right angles to each other and about 2 feet seperated on the pole.
There is no easy way to know if an AP is being desensed (or getting spurious radiation from the other AP) or not I guess. With the high power AP off, maybe I could continuously ping the lower power AP and walk away with my client device until I get a very weak signal. Walk away until I just barely lose the signal. Then turn on the 500 mW AP. If it is giving a problem, my continuous pinging should stop due to interference. That would be a test I guess.
Thats neat you have 3 APs in WDS. I never did WDS before, but am just now thinking of it for a hotel. I understand you lose throughput. Like if you have 2 APs on WDS, your throughput is cut in half. I guess if you have 3 APs in WDS your throughput is cut to 1/3. But maybe thats not so bad cause you probably still have 1 or 2 Mbit connection to the APs.
How much signal level do I need between two APs in WDS mode in order to properly run WDS? Is one AP in regular AP mode and the other AP in WDS or are both in WDS mode?
Thanks much, |
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Airplane777
join:2004-06-20
| reply to jimg_comp
Hello jimg_comp:
Thank you also for your input.
Thats great then that you have them operating so close on different channels, but with no apparent problems.
That would be neat if you could do a continuous ping on one with the other one turned off. Walk away until you get a very weak received signal strength. Then have someone turn on the other AP. And see if your continuous pinging keeps working. If it does, then you would have no problems.
If you try that test, please let us know how it worked.
Thaks again for your input, |
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redpanther
join:2001-01-07
Hot Springs National Park, AR
·AT&T Southwest
·Cablelynx
| reply to Airplane777
I don't know what the minimum signal is for WDS to work as I haven't stretched my aps to find the limits.
In the testing I did with my setup I can hit any of the 3 aps with my laptop. The throughput didn't appear to drop terribly.
UDP Streaming throughput was the same wether going through 1,2 or all 3. TCP was another matter... I lost about 5 kbps going through all 3. All 3 introduced appx. 3 ms of extra lag.
I don't know how this would affect gaming ability but for surfing works great. I will be testing the gaming later on.
What I'm running is 2 Linksys WRT54G (Sevasoft firmware)and 1 Buffalo WBR-54G.
By the way, all 3 have to be set for WDS. |
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DSLrgm
Premium,MVM
join:2002-08-22
Oak Park, MI
| reply to Airplane777
said by Airplane777  :Anyone know if there is any study done on whether two APs operating near each other can cause detrimental operation to each other? To get some presentations from the July 802 plenary related to this go to:
»homebase.htt-consult.com/~rgm/ess-mesh/
And get the following presentations:
11-04-0760-00-000s-mac-considerations-mesh.ppt
11-04-0732-01-000s-outdoor-802-11-mesh-mac-protocol-issues-and-considerations.ppt
11-04-0731-00-000s-outdoor-802-11-mesh-links-rf-impacts-considerations.ppt
11-04-0709-02-000s-multi-hop-connections-using-802-11.ppt |
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