Access Point Height , RRM (Auto RF) and Warehouse

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Sep 15th, 2009
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Hello Experts,

I have a Warehouse situations where there is a high density Access Point deployment. The APs are 1242 with external antennas. The height at which these antennas are mounted is 30 feet.

The clients (Scanners) are complaining poor signal. I also see several Access Points powered down to level 8 due to high density.

My question is is it possible that due to Auto RF (RRM) that the APs have reduced the power such that by the time signal reaches the client it is very week.

What is the maximum height allowed on these 1240s in an indoor environment.

Has anybody seen something like this.

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Leo Laohoo Tue, 09/15/2009 - 14:47
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Are you using autonomous or controller-based AP?

Have you done a walk around with a spectrum analyzer to find out if the channels are interfering with each other?

desaikeyur Wed, 09/16/2009 - 07:09
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The antennas are omnidirectional 2db antennas. And the warehouse is used for scanners.

The scanners have the following specs

Transmit Power 32mW max (+15dBm), all versions

Frequency Range 2.400 - 2.4835 GHz, all versions

Channels 1 to 11 for USA, Canada

1-13 for EU countries

RX Sensitivity (8% FER, 1024 bytes packet) =

-89dBm @ 1 Mbps, -87dBm @ 11 Mbps,

-83dBm @ 6 Mbps, -72dBm @ 54 Mbps

I am going to try your recommendation and check the threshold and see if that makes any difference. I am also concerned about the co channel as scanner use g only.

desaikeyur Mon, 09/28/2009 - 09:19
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Thanks Aaron, I am leaning towards changing the RRM settings. But here is some more information that can help you assist me better.

Changing Antenna is not an option. Also I believe the null under one antenna should be covered by another AP in the neighborhood. Unless the AP height of 28ft - 30ft,causes the signal to drop drastically by the time it reaches the client.

astronotus Wed, 10/07/2009 - 00:42
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I'm currently working in an environment similar to what you say, with the same access points, the same omnidirectional antennas and the same distribution and location of antennas (30ft).

The problem I have is interference with other wireless networks, but I think that could be solved, at least in part, by varying the parameter TX power treshold according you propose. I think that the APs can hear each other very well so their antennas are located quite high, but clients, especially when there are other wireless networks, do not hear so well the APs from the floor.

Do you think that if I change this parameter I can solve the problem?

I tested with the parameter TX power treshold in -65 and -70. Should I therefore upload it to -55 or reduce it to -80?



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