Bug in TPC calculation?

[patoberli]

Hello

I think I have an issue with TPC on 8.2.161.0.

I have this just discovered, because I had bad coverage in an area. After checking the AP on the WLC, I saw it's running with power 4, and some minutes later, power setting 5.

I'm fairly sure I lack one command output, but here are some, which should, based on what I remember, provide much higher power settings:

(Cisco Controller) >show ap auto-rf 802.11b 3702AC-1U00K-1

Number Of Slots.................................. 2 
AP Name.......................................... 3702AC-1U00K-1
MAC Address...................................... 74:a2:e6:60:9c:d8
  Slot ID........................................ 0
  Radio Type..................................... RADIO_TYPE_80211b/g
  Sub-band Type.................................. All
  Noise Information
    Noise Profile................................ PASSED
    Channel 1....................................  -97 dBm
    Channel 2....................................  -98 dBm
    Channel 3....................................  -94 dBm
    Channel 4....................................  -97 dBm
    Channel 5....................................  -96 dBm
    Channel 6....................................  -94 dBm
    Channel 7....................................  -97 dBm
    Channel 8....................................  -97 dBm
    Channel 9....................................  -94 dBm
    Channel 10...................................  -97 dBm
    Channel 11...................................  -95 dBm
    Channel 12...................................  -93 dBm
    Channel 13...................................  -96 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
    Rogue Histogram (20)
    ............................................. 
    Channel 1....................................  1
    Channel 2....................................  0
    Channel 3....................................  0
    Channel 4....................................  0
    Channel 5....................................  0
    Channel 6....................................  0

--More-- or (q)uit
    Channel 7....................................  0
    Channel 8....................................  0
    Channel 9....................................  0
    Channel 10...................................  0
    Channel 11...................................  0
    Channel 12...................................  0
    Channel 13...................................  0
  Load Information
    Load Profile................................. PASSED
    Receive Utilization.......................... 0 %
    Transmit Utilization......................... 0 %
    Channel Utilization.......................... 0 %
    Attached Clients............................. 1 clients
  Coverage Information
    Coverage Profile............................. PASSED
    Failed Clients............................... 1 clients
  Client Signal Strengths
    RSSI -100 dbm................................ 0 clients
    RSSI  -92 dbm................................ 0 clients
    RSSI  -84 dbm................................ 0 clients
    RSSI  -76 dbm................................ 1 clients
    RSSI  -68 dbm................................ 0 clients
    RSSI  -60 dbm................................ 0 clients

--More-- or (q)uit
    RSSI  -52 dbm................................ 0 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.................................. 1 clients
    SNR   30 dB.................................. 0 clients
    SNR   35 dB.................................. 0 clients
    SNR   40 dB.................................. 0 clients
    SNR   45 dB.................................. 0 clients
  Nearby APs
    AP 28:6f:7f:b3:4a:e0 slot 0..................  -92 dBm on   1  20MHz (172.16.102.11)  2802AC-1018-1
    AP 28:c7:ce:4f:54:80 slot 0..................  -98 dBm on  11  20MHz (172.16.102.11)  3502AGN-1159-1
    AP 2c:3f:38:5a:b4:a0 slot 0..................  -96 dBm on   1  20MHz (172.16.102.11)  3502AGN-1016-1
    AP 6c:50:4d:ab:84:00 slot 0..................  -96 dBm on   1  20MHz (172.16.102.11)  3502AGN-1100c-2
    AP 6c:50:4d:b7:99:e0 slot 0..................  -98 dBm on   6  20MHz (172.16.102.11)  3502AGN-1100a-2
    AP 74:a2:e6:71:5b:10 slot 0..................  -75 dBm on  11  20MHz (172.16.102.11)  3702AC-1100g-1
    AP 74:a2:e6:78:d1:20 slot 0..................  -94 dBm on   1  20MHz (172.16.102.11)  3702AC-1015-1
    AP b4:e9:b0:9e:e3:20 slot 0..................  -98 dBm on  11  20MHz (172.16.102.11)  3502AGN-1177a-1
    AP b4:e9:b0:ae:79:c0 slot 0..................  -98 dBm on   1  20MHz (172.16.102.11)  3502AGN-1164-1
  Radar Information

--More-- or (q)uit
  Channel Assignment Information
    Current Channel Average Energy...............  -82 dBm
    Previous Channel Average Energy..............  -82 dBm
    Channel Change Count......................... 1
    Last Channel Change Time..................... Tue Jun 12 17:49:00 2018
    Recommended Best Channel..................... 1
  RF Parameter Recommendations
    Power Level.................................. 4
    RTS/CTS Threshold............................ 2347
    Fragmentation Threshold...................... 2346
    Antenna Pattern.............................. 0

  Persistent Interference Devices
  Class Type                 Channel  DC (%%)  RSSI (dBm)  Last Update Time
  -------------------------  -------  ------  ----------  ------------------------
  Microwave Oven             11       9       -73         Wed Jun 20 12:32:12 2018   
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  (Cisco Controller) >show advanced 802.11b txpower         

Leader Automatic Transmit Power Assignment
  Transmit Power Assignment Mode................. AUTO
  Transmit Power Update Interval................. 600 seconds
  Transmit Power Threshold....................... -74 dBm
  Transmit Power Neighbor Count.................. 3 APs
  Min Transmit Power............................. -10 dBm
  Max Transmit Power............................. 30 dBm
  Update Contribution
    Noise........................................ Enable
    Interference................................. Enable
    Load......................................... Disable
    Device Aware................................. Disable
  Transmit Power Assignment Leader............... wlc-5520-1 (172.16.102.11) (::)
  Last Run....................................... 54 seconds ago
  Last Run Time.................................. 0 seconds
  TPC Mode....................................... Version 1
  TPCv2 Target RSSI.............................. -67 dBm
  TPCv2 VoWLAN Guide RSSI........................ -67.0 dBm
  TPCv2 SOP...................................... -85.0 dBm
  TPCv2 Default Client Ant Gain..................   0.0 dBi
  TPCv2 Path Loss Decay Factor...................   3.6

--More-- or (q)uit
  TPCv2 Search Intensity......................... 10 Iterations
  
[output of all other APs removed, only left my sample AP]

  3702AC-1U00K-1                   *1         *4/5 ( 7 dBm) [16/13/10/7/4/4/4/4]
  
  

What do you think? Shouldn't the AP run with Power 1 or maybe 2?

[Flavio Miranda]

Hi

 Countless times I've seeing RRM acting totally inappropriate. Not only for power but channel as well. Totally no sense.

[Scott Fella]

Not saying that RRM is useless but if you do run into a bug can definitely hurt. This is with all vendors also. I tend to verify with tools like NETSCOUT to look at the signal from adjacent AP’s to determine if I need to tweak the RF especially if it’s a sparse deployment or not a proper design. 

[patoberli]

True. In this specific case it's an AP in a concrete cellar, which is why it doesn't see any neighbors (but one) with a somewhat strong signal.

I'm not going to spend too much time with this issue, because I'm upgrading to 8.5.131.0 next week, but was still surprised to see this.

[Scott Fella]

If it’s the only AP in an isolated area, yes it should be on TX power of 1. Default for RRM is theee at -75 unless the value was changed. 

[patoberli]

I turned it down to -76, but yeah, TX power should be 1. It's really weird, but I'm fairly sure it's some weird bug :)

[Scott Fella]

How is your other AP’s? I tend to use the max and min TX setting to control power but let RRM handle the channel changes. At home, I hard set the TX power due to EDRRM and all the wireless around my home, including my Meraki setup.

[patoberli]

Checked a few other buildings, where I know is the coverage low, but there they run at full power.
I've rebooted that one AP now, let's see if this will change anything.

[patoberli]

Updated the WLC last week to 8.5.131.0 and since a few TPC runs is the AP now at the expected power level 1 instead of 5 (or 4).

Not sure if the reboot helped or the new software.

The other Aps seem to have kept their power levels, at least Prime doesn't show a shift to more or lower power over the whole network.