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New Member

High Density deployment

Hi

 

I've inherited a wireless deployment at a multi floor office that is using 5508 controllers and 1142n AP.

There have been reports of wireless connectivity issues at the site in certain areas on the 2.4Ghz spectrum. It seems all the AP's are transmitting at very low power (power level 7 or 8).

I have seen one diagram of one floor and it looks like the AP's are close together (around 8-10 meters apart).

This floor is a manufacturing floor with relatively low client density and throughput requirements. they average only 3 or 4 client per AP. At the whole site today I see 60 clients across 45 AP's....

No heavy machinery or racking that I am aware of.

I do not have a a copy of the original site survey specifications but I thinking it was designed with lower data rates disabled and transmit powers at 50% (for AP redundancy)

Here is an example from one AP.

 

(Cisco Controller) >show ap auto-rf 802.11b AP009

Number Of Slots.................................. 2
AP Name.......................................... AP009
MAC Address...................................... 70:ca:9b:6c:aa:76
  Slot ID........................................ 0
  Radio Type..................................... RADIO_TYPE_80211b/g
  Sub-band Type.................................. All
  Noise Information
    Noise Profile................................ PASSED
    Channel 1....................................  -97 dBm
    Channel 2....................................  -92 dBm
    Channel 3....................................  -80 dBm
    Channel 4....................................  -91 dBm
    Channel 5....................................  -92 dBm
    Channel 6....................................  -93 dBm
    Channel 7....................................  -93 dBm
    Channel 8....................................  -91 dBm
    Channel 9....................................  -92 dBm
    Channel 10...................................  -88 dBm
    Channel 11...................................  -93 dBm
    Channel 12...................................  -85 dBm
    Channel 13...................................  -94 dBm

--More-- or (q)uit
  Interference Information
    Interference Profile......................... PASSED
    Channel 1.................................... -128 dBm @  0 % busy
    Channel 2.................................... -128 dBm @  0 % busy
    Channel 3.................................... -128 dBm @  0 % busy
    Channel 4.................................... -128 dBm @  0 % busy
    Channel 5.................................... -128 dBm @  0 % busy
    Channel 6.................................... -128 dBm @  0 % busy
    Channel 7.................................... -128 dBm @  0 % busy
    Channel 8.................................... -128 dBm @  0 % busy
    Channel 9.................................... -128 dBm @  0 % busy
    Channel 10................................... -128 dBm @  0 % busy
    Channel 11................................... -128 dBm @  0 % busy
    Channel 12................................... -128 dBm @  0 % busy
    Channel 13................................... -128 dBm @  0 % busy
  Load Information
    Load Profile................................. PASSED
    Receive Utilization.......................... 0 %
    Transmit Utilization......................... 13 %
    Channel Utilization.......................... 64 %
    Attached Clients............................. 1 clients
  Coverage Information
    Coverage Profile............................. PASSED

--More-- or (q)uit
    Failed Clients............................... 0 clients
  Client Signal Strengths
    RSSI -100 dbm................................ 0 clients
    RSSI  -92 dbm................................ 0 clients
    RSSI  -84 dbm................................ 0 clients
    RSSI  -76 dbm................................ 0 clients
    RSSI  -68 dbm................................ 0 clients
    RSSI  -60 dbm................................ 0 clients
    RSSI  -52 dbm................................ 1 clients
  Client Signal To Noise Ratios
    SNR    0 dB.................................. 0 clients
    SNR    5 dB.................................. 0 clients
    SNR   10 dB.................................. 0 clients
    SNR   15 dB.................................. 0 clients
    SNR   20 dB.................................. 0 clients
    SNR   25 dB.................................. 0 clients
    SNR   30 dB.................................. 0 clients
    SNR   35 dB.................................. 0 clients
    SNR   40 dB.................................. 0 clients
    SNR   45 dB.................................. 1 clients
  Nearby APs
    AP 00:08:30:4b:20:90 slot 0..................  -20 dBm on  11 (xx.xx.xx.xx)
    AP 00:08:30:a7:ca:c0 slot 0..................  -62 dBm on   6 (xx.xx.xx.xx)

--More-- or (q)uit
    AP 00:08:30:d7:de:90 slot 0..................  -60 dBm on  11 (xx.xx.xx.xx)
    AP 24:b6:57:7a:52:80 slot 0..................  -24 dBm on  11 (xx.xx.xx.xx)
    AP 24:b6:57:7a:90:20 slot 0..................  -28 dBm on   6 (xx.xx.xx.xx)
    AP 3c:ce:73:6d:91:f0 slot 0..................  -47 dBm on   6 (xx.xx.xx.xx)
    AP 58:bf:ea:25:6f:20 slot 0..................  -68 dBm on   6 (xx.xx.xx.xx)
    AP 58:bf:ea:25:90:f0 slot 0..................  -71 dBm on   1 (xx.xx.xx.xx)
    AP a4:18:75:18:f4:40 slot 0..................  -49 dBm on   1 (xx.xx.xx.xx)
    AP a4:18:75:19:21:50 slot 0..................  -69 dBm on   1 (xx.xx.xx.xx)
    AP a4:18:75:19:2f:30 slot 0..................  -47 dBm on   1 (xx.xx.xx.xx)
    AP a4:18:75:19:ff:a0 slot 0..................  -65 dBm on  11 (xx.xx.xx.xx)
    AP a4:18:75:42:b5:c0 slot 0..................  -53 dBm on   1 (xx.xx.xx.xx)
    AP a4:18:75:65:bf:b0 slot 0..................  -71 dBm on  11 (xx.xx.xx.xx)
    AP a4:18:75:65:d3:20 slot 0..................  -68 dBm on   6 (xx.xx.xx.xx)
    AP a4:18:75:65:db:70 slot 0..................  -69 dBm on   6 (xx.xx.xx.xx)
    AP a4:18:75:78:a8:a0 slot 0..................  -68 dBm on   6 (xx.xx.xx.xx)
    AP a4:18:75:78:b8:c0 slot 0..................  -53 dBm on  11 (xx.xx.xx.xx)
    AP a4:18:75:78:bc:d0 slot 0..................  -71 dBm on  11 (xx.xx.xx.xx)
    AP c8:f9:f9:29:26:30 slot 0..................  -41 dBm on   1 (xx.xx.xx.xx)
    AP f4:ea:67:c1:62:c0 slot 0..................  -59 dBm on  11 (xx.xx.xx.xx)
  Radar Information
  Channel Assignment Information
    Current Channel Average Energy............... unknown
    Previous Channel Average Energy.............. unknown

--More-- or (q)uit
    Channel Change Count......................... 0
    Last Channel Change Time..................... Thu Mar 20 15:38:50 2014
    Recommended Best Channel..................... 1
  RF Parameter Recommendations
    Power Level.................................. 8
    RTS/CTS Threshold............................ 2347
    Fragmentation Threshold...................... 2346
    Antenna Pattern.............................. 0

Do you think these low transmit powers could be causing an issue?

We statically configured the power on an AP in an area that was having an issue to 4 and this helped. However, I don't want to do this everywhere and realise that we should either use RRM everywhere or not all.

I have a few ideas and would appreciate some input (are my assumptions correct :) ?) Any other ideas?

Option 1

Remove 11b Data rates. We do not see any 11b clients connecting at that site so we could disable rates 1 to 11. My understanding (and please correct if wrong). Is that this will decrease the cell size. But would it help the transmit power at all? I'm guessing that if the lower data rates are disabled then the other AP's that are currently heard at rates 1 - 11 would not be heard now (they would just appear as noise on the channel) and this in turn would allow the TX power to be increased. The drawback would be that the co-channel interference (or noise) would also increase as the wireless signals propagate further?

Options 2

Tweak the TX power options under RRM. Again, any good advice here? or should option 1 be enough?


Any input much appreciated

5 REPLIES
Hall of Fame Super Silver

Can the TX power your seeing

Can the TX power your seeing be an issue.... yes it can.  TX power that low tend to make devices associate with other AP's that have a higher TX power, thus sometimes making roaming decisions tricky for the device.  What you need to tweak and adjust until your environment is fine, is setting your max TX to maybe 14dbm and your min TX to 8 or even 5.  Then look at your output and see what RSSI and SNR clients are associated at.  This will tell you your signal from the client aspect in a way.  Depending on the code version, you might have to disable the radio's in order to change the max and min TX power.  I would also consider, if your lower data rates and 802.11b are disabled, that you set your mandatory rate at 54mbps and 24mbps and look at the output for RSSI and SNR.  TX power and data rates.... you can tweak to adjust the cell size.  Now if you do have 802.11b devices, then you need to understand the minimum data rate that those devices require.

Scott

-Scott
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Hall of Fame Super Silver

Also..... your comment, "No

Also..... your comment, "No heavy machinery or racking that I am aware of."  You're better off going out there if you really want to tweak the environment.  There is only so much you can do remote and being onsite, you can see how the environment might affect your RF.  Heck... your AP's and or antennas might be mounted wrong or in an angle that is not correct.  This is from experience.... onsite is the way to go.

Scott

-Scott
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New Member

Thanks Scott.We'll look at

Thanks Scott.


We'll look at disabling the lower rates first. Cisco Prime does not see any 802.11b clients over the last 7 days. I may go to the site as well and verify everything looks OK.

I'll try to post any results back to the forum

New Member

Thanks Scott, Just to clarify

Thanks Scott,

 

Just to clarify. We still have 802.11b rates enabled. So does it still make sense to disable these as a first step before changing TX power?

And with reference the power levels. I've been using the levels 1 - 8 as shown on the WLC. I've not been referencing the actual TX power in dBm.  In you reply "max TX to maybe 14dbm and your min TX to 8 or even 5" I am not sure if you are referring to the WLC TX values or actual dBm values. Would you be able to clarify for me please?

 

Thanks again for the great info

Hall of Fame Super Silver

Just to clarify. We still

Just to clarify. We still have 802.11b rates enabled. So does it still make sense to disable these as a first step before changing TX power?

> Only if you know that you don't have any 802.11b devices... I would disable 11mbps and below to start

And with reference the power levels. I've been using the levels 1 - 8 as shown on the WLC. I've not been referencing the actual TX power in dBm.  In you reply "max TX to maybe 14dbm and your min TX to 8 or even 5" I am not sure if you are referring to the WLC TX values or actual dBm values. Would you be able to clarify for me please?

> You can set the max TX and min TX that an access point will use:

 

Scott

-Scott
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