3700 Transmitting Low Power on the 2.4Ghz Range

[John Lee]

Hello;

I am having problems getting the 3700 APs to transmit on full power, I have 22 registered with my WLC and around half are displayed the message:

"Due to low PoE radio is transmitting at degraded power" and are only transmitting on Power Level 6, where as others are transmitting at a higher rate.

All switchports have been configured to allow the maximum power allowed.

This is only occuring on the 2.4Ghz range and not the 5Ghz.

Any ideas? I am running software version 7.6.120.

Thanks;

John

[Rasika Nayanajith]

Hi John,

What is the switch model you used to power these AP ? Switch has to be PoE+ to provide enough power to make all radio chains up.

Post "show power inline gx/x detail" output where x/x is the 3702 connected switchport

HTH

Rasika

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[John Lee]

Hi Rasika;

The model of switch is a Cisco WS-C3750X-48P - This model does have PoE+, I have also set the static power to maximum in an attempt to over come this issue:

#SHOW POWer INline gigabitEthernet 1/0/48 detail
 Interface: Gi1/0/48
 Inline Power Mode: static
 Operational status: on
 Device Detected: no
 Device Type: cisco AIR-CAP3702I-
 IEEE Class: 4
 Discovery mechanism used/configured: Unknown
 Police: off

 Power Allocated
 Admin Value: 30.0
 Power drawn from the source: 30.0
 Power available to the device: 30.0

 Actual consumption
 Measured at the port: 6.3
 Maximum Power drawn by the device since powered on: 7.1

 Absent Counter: 0
 Over Current Counter: 0
 Short Current Counter: 0
 Invalid Signature Counter: 0
 Power Denied Counter: 0

 Power Negotiation Used: CDP
 LLDP Power Negotiation --Sent to PD--      --Rcvd from PD--
   Power Type:          -                    -
   Power Source:        -                    -
   Power Priority:      -                    -
   Requested Power(W):  -                    -
   Allocated Power(W):  -                    -

Thanks;

John

[Sandeep Choudhary]

Hi John,

Just give a try:

Try to enabled cdp on both side on swicth port and as well as on AP side.

and then paste the output from swicth: sh power inline gigabitEthernet 1/0/48 detail

Its also depends on MIMO:

Also chekc this post: https://supportforums.cisco.com/discussion/12029796/cisco-ap-3700-poe

Regards

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[John Lee]

Hello;

Here is the output from the switch and an image showing the alert:

XXXXX003#show power inline gigabitEthernet 1/0/48
Interface Admin  Oper       Power   Device              Class Max
                            (Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Gi1/0/48  static on         30.0    AIR-CAP3702I-E-K9   4     30.0

Interface  AdminPowerMax   AdminConsumption
             (Watts)           (Watts)
---------- --------------- --------------------

Gi1/0/48              30.0                 30.0

[singhmanaspratap]

Hi John,

The APs are transmitting low power level on 2.4 GHz because of RRM feature on the WLC.

This happens when the APs are quite close to each other and there is interference. Did we go through the process of site survey before AP installation?

Thanks and regards,

Manas Pratap Singh

[John Lee]

Hello;

The APs actually give the reason "Due to low PoE radio is transmitting at degraded power" so I don't think it is because of the RRm feature.

There was a site survey before the instal and using Prime I can see there are a few coverage holes because of the low power.

Thanks;

John

[Sandeep Choudhary]

Hi,

You set the radio power manually if you want:

Wireless > Access Points > Radios > 802.11b/g/n and the on the AP far right side their is a blue arrow. click on configure.

then under Tx Power Level Assignment section you use assignement method as custom and make it to 1.

Regards

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[singhmanaspratap]

Hi Sandeep,

I think setting the power manually to 1 would overwrite the RRM feature of WLC.

John,

You are getting coverage hole alarms because the Basic Service Area or Access points are not overlaping each other properly.Once they overlap with 15-20% RRM feature would assign the power level based on that.

Are we using POE Switches for APs or its getting power from Power supply. If from POE please let me know the model of the AP and use show power inline command on the switch and share the output

Thanks and regards,

Manas Pratap Singh

[Sandeep Choudhary]

Agree MPS.

But when anybody need it then he must have to do it manually.

@John: AS MPS told, its always good to do a proper site survey before WLAN implementation otherwise you will face problem like this everyday...

Regards

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[John Lee]

Hello;

I did conduct a full and proper site survey before implementation.

The alarms I am getting are not coverage hole alarms but are suggesting there are problems with the PoE+ on the AP.

The attached output is on the comment below.

[Dhiresh Yadav]

Hi,

"Due to low PoE radio is transmitting at degraded power"...Who is making this statement ? Is this message in any log ? Go to AP > Advanced and check POE status. If it is saying , not a full power , then check , "sh power inline" to see how much power switch is providing.If it is with out any module , and you provide only 15.4 which means switch not POE+ capable..then one SS will be reduced.

Coming to the conclusion you made about Power level 6 , you are trying to mix two separate things. If there is a less power for example 15.4 it will reduce one SS but in both the bands 2.4/GHz. Power level 6 which is reduced by RRM in 2.4 only is due to normal RRM calculations 

Regards

Dhiresh

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[Todd S]

Did you ever have a solution to this issue?  I'm having a similiar issue with 2702's and non Cisco 802.3af/at capable switches.

[majhensgens]

As mentioned by others your WLC is trying to compensate for the strong 2.4 GHz signals and lowers the maximum power level by 1 for each iteration of RRM. This happens when three of the neighboring Access Points have a signal that is stronger than -70 dBm (default). When this happens you should look to disable some 2.4 GHz radios to compansate for to much signal. (But that is situation dependable)

Second look at your power budget with the Sh power inline command (without the interface) and look at your remaining (watts). Normally an PoE+ Switch would provide a maximum on 15.4 Watts on all ports at once. This means you could (switch dependable) only use 16 ports or so with a power drawage of 30 watts.
 For example the switch you use has only 715 watts of power.This means when the switch needs to provide power to all ports at the same time for all of your devices, it could only provide an maximum of 14.95 watts per port.

[Todd S]

Unfortunately the 5GHz radios are showing the same message and are at power level 1.  As I mentioned before, the customer I'm working with isn't running a Cisco infrastructure.

The switches used in the infrastructure have plenty of power to be able to provide enough PoE power, 855 watts, to power the 10 PoE devices, all Cisco 2702's.