Basic question regarding 802.11a power levels

Unanswered Question

I am trying to verify something regarding the 802.11a power settings using a WLC:

If the power setting for the 802.11a radio is a divisor (i.e.: Power setting of "1" is full power, power setting of "2" is half power, etc.), how am I to interpret the settings that the max power setting for "lower" channels (5150 to 5250 MHz chan 36-48 FCC) is limited to a lower transmit power (i.e.: 15 dBm) than the transmit power for other "higher" channels (uni 3 from 5725 to 5850 MHz chan 149-161 FCC) which is able to transmit at 17 dBm.

Please refer to table Table 3-3 to in the following document:

http://www.cisco.com/en/US/docs/wireless/access_point/channels/lwapp/reference/guide/1130_chp.html

In other words, what is being divided? The 15dBm or the 17dBm? Does changing the channel from a lower-numbered channel in the 5150 to 5250 MHz range to a higher-numbered channel in the 5725 to 5850 MHz range result in an increase in power (since the max transmit power is now higher)?

Or to phrase it a different way, when my power setting on the WLC is "1" for an 1131AG access point, what is my transmit power level? 15 or 17dBm? Does the power level vary - depending upon which channel I choose?

- John

I have this problem too.
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dennischolmes Fri, 08/22/2008 - 12:53

I would suspect that it is limited by the channel you select but will ask for clarification from our friends at Cisco.

Scott Pickles Tue, 11/10/2009 - 11:05

This is an old post, but you can verify what power level (in dBm) your AP is running by using the cli command 'show ap config 802.11a ' and yes, it does vary by channel.

dennischolmes Thu, 11/26/2009 - 10:11

Good post. Here is part of your data.

UNII 1                                                 UNII 2 / 3

1 = 11 dBm / 12.5 mW                          1 = 17 dBm / 50mW
2 = 8 dBm / 6.25 mW                            2 = 14 dBm / 25 mW
3 = 5 dBm / 3 mW                                3 = 11 dBm / 12.5 mW
4 = 2 dBm / 1.5 mW                              4 = 8 dBm / 6.25 dBm

This is VERY important when planning a network in WCS planning tool or Airmagnet Planner.

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