Question about TXPower (WLC9K8 and C9120AXI-E AP)

[nanu]

Hi,

We are facing some strange behaviuor regarding the txpower of C9120AXI-E power, i will show you some outputs (I sanitized the output for privacity reasons), this is the output of show ap dot11 24Ghz summary:

AP1 MACXXXX 0 Enabled Up 20 *1/7 (12 dBm) (11)* REAP
AP2 MACXXXX 0 Enabled Up 20 *1/7 (12 dBm) (1)* REAP
AP3 MACXXXX 0 Enabled Up 20 *3/7 (6 dBm) (11)* REAP
AP4 MACXXXX 0 Enabled Up 20 *2/7 (9 dBm) (6)* REAP

As far I known, the 1/7 means from 7 levels of power, 1 Is the maximum available, 2 will be 50%, 3 will be 25%... that's correct?

The Quesiton is, why at maxium 1/7 ths AP only transmit to 12dBm when per datahseet the has more power?

Thank you,

[Jurgens L]

Not the 9120's, check the datasheet, they still operate at 13.4W but with 1x1 radios in dual-band. From the WLC, the power level in my test did not decrease, the AP was still on level 7 however the dBm value did drop by 3 which was also interesting to me.

When I force the AP to be on Level 1 at 25.5W PoE I get 23dBm, then when I force the power inline to 15.4W the antenna gets 20dBm, still on Level 1.

[nanu]

Hi,

From the AP point of View:

This devices are connected to WS-C2960S-48PS-L, I request a "show power inline" because i don't have direct access to the final devices.

Apreciate your effort!

[pieterh]

Hi Jurgens,
I value your information, I guess you refer to this part of the table ?

PoE power consumption

2.4-GHz radio

5-GHz radio

Link speed

USB

LLDP

802.3af

PoE

1x1

1x1

1G

N

13.4W

802.3af

PoE

2x2

N

1G

N

13.4W

802.3af

PoE

N

2x2

1G

N

13.4W

looks there are several possibilities which and how many radios are participating while using same PoE power

Good to know!

[nanu]

Hi Team,

Sorry for my late response.  I attach the capture about power supplied, as you can see the switch looks likes is offering 30W but the AP is only getting 15.4W, how can we force the 30W?

Thank you!

[pieterh]

>>> how can we force the 30W <<<

why should you want to ??? all devices currently try to save energy when not needed!
- the switch is capable of providing 30W
- the AP requested 30W max (! NB!!! max!)

- the switch assigned 30W max

but the AP is currently using only 15.4W ,
this is no problem, the features currently activated on the AP require only 15.4W
e.g. the   USB 2.0 @ 3.75W (enabled via future software) is not in use, so will not consume any power

if you stress your AP with many clients so both bands are fully utilized with all radio's active and all spatial streams (4x4)
and the CPU load increases, then your power drawn from the switch wil rise dynamically
BUT even then it will possilbly not reach 30W but keep below 21.7W (25.4-3.75W reserved for when usb is used)
only if you also use a long cable over which you will lose a lot of power between sent at the switch and received by the AP than maybe you come near 30W.

[nanu]

Hi,

Well... I don't udnerstand then why isn't not trasmiting at maximum power...

Thank you,

[jvodeb]

Hello,

do we have any new information regarding this? What did TAC say?

Regards,

Julijan

[Tony Rosolek]

I'm also interessted in the solution to that topic. Can someone please post an update? Did someone raise a TAC case?

@Jurgens L good findings, related to PoE power and transmit power. Thanks for sharing!