Tx power for Cisco 7925G and 7921 IP Phone

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Apr 8th, 2010
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I have a problem with 7925G IP phones. While performing site survey with 7921 and 7925G phones, i have noticed that voice quality is poor on 7925 while 7921 still working properly. I have WLC5508 and 4404 version 6 and 1121, 1131 and 1141 APs and I'am using 802.11b/g/n. TPC is set to the maximum "1" and DCA is fixed, WMM is set to Allowed, QOS to Silver. I have also noticed that tx power for 7921 is 17dBm and for 7925 it is 14dBm. I have tried upgrading 7925 firmeware to 1.3.4 which was 1.3.3, also tried change "Call power save mode" to none and still have the same problem.

I would like to know if there is a way to change tx power of the 7925 to its maximum which is 16dBm for OFDM and 17dBm for CCK.

Any help is appreciated.

Thank you

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mlieber Wed, 03/16/2011 - 07:01
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I know your question was long time ago.

But do you have got a solution for the issue?

I have the same problem, the 7921 are working properly but the 7925 jhave poor quality.



quehli Mon, 05/09/2011 - 06:37
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Did have the same issue! Only solution was to set on the access points the value

interface dot11radio0
world-mode dot11d country US both
interface dot11radio1
world-mode dot11d country US both



c_baaklini Mon, 05/09/2011 - 22:37
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For the time being there is no solution for this problem, as informed by Cisco support. The work arround solution was by installing addidtional access points.

On the antenna side, the 7925 is a single antenna, so non-diversity, where the 7921 does have dual antennas to provide diversity.


Leo Laohoo Mon, 05/09/2011 - 22:53
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Unfortunately the 7921's antenna gets dislodged easily when the unit falls on a certain angle.

migilles Mon, 08/01/2011 - 23:36
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Fyi, the 7921s antennas are bound to the board.

Currently max tx power for 2.4 GHz on the 7925 for European countries is 14 dBm.

Currently investigating to whether the tx power can be increased by 3 dB to 17 dBm for European countries or not per compliance regulations.

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migilles Mon, 08/01/2011 - 23:37
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As always 5 GHz is the recommended band to use for VoWLAN.

Can do up to 17 dBm in 5 GHz for European countries.

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