Wireless Access

Is there any specific reason in having max transmission power vary over the channel of operation?

(WLC_0002) # show ap allowed-max-EIRP ap-name P-AP1

Max EIRP setting for AP-277
---------------------------
Channel  1   2   3   4   5   6   7   8   9   10  11  12  13  14  36  40  44  48  52  56  60  64  100  104  108  112  116  120  124  128  132  136  140  144  149  153  157  161  165
-------  -   -   -   -   -   -   -   -   -   --  --  --  --  --  --  --  --  --  --  --  --  --  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---  ---
b        33  33  33  33  33  34  34  34  33  33  33  *   *   *   *   *   *   *   *   *   *   *   *    *    *    *    *    *    *    *    *    *    *    *    *    *    *    *    *
g/a      33  33  33  34  34  34  34  34  33  33  33  *   *   *   31  31  31  31  23  23  23  23  22   22   22   22   22   22   22   22   22   22   22   22   31   31   32   31   31
HT 20    31  31  31  31  31  31  31  31  31  31  31  *   *   *   28  28  28  28  20  20  20  20  20   20   20   20   20   20   20   20   20   20   20   20   29   29   29   29   29
HT 40    31  31  31  31  31  31  31  31  31  31  31  *   *   *   28  28  28  28  23  23  23  23  22   22   22   22   22   22   22   22   22   22   22   22   28   28   28   28   28
VHT 80   *   *   *   *   *   *   *   *   *   *   *   *   *   *   28  28  28  28  22  22  22  22  22   22   22   22   23   23   23   23   22   22   22   22   25   25   25   25   25

Those are the regulatory limits set per channel as part of the certification process. Not al chanenls will carry the same max EIRP as you move in and out of different UNI bands and as it changes HT bandwidths.

Thanks Jerrod,

Is there a standard database which could be referred to obtain the max EIRP against individual channel of 5GHz for each individual regulatory domain?

Additionally while going through below document, appears certain channels(149  153  157  161  165) are designated as "short range devices" for certain regulatory domain. Is there any specific reason/logic for it to make operate for a transmission power not exceeding 25 mw?

http://www.radio-electronics.com/info/wireless/wi-fi/80211-channels-number-frequencies-bandwidth.php

You can get it from the controller with 'show ap allowed-max-eirp' but it's not published, mostly due to the fact that it changes fairly regularly country to country and as soon as it's published, it may be out of date when a country changes policy, and it's different from AP to AP as well. Generally, esp indoors, you don't run at the max allowed EIRP anyway so the point is moot in most all cases indoors. Outdoors, we make sure our APs are certified to the highest powers allowed and then will down rate in software to be regulatorily compliant.

Also adding, at least in US, 25mW is NOT the max for outdoor 5Ghz. It might be in other countries (ETSI cited in one case). 25mW for ETSI outdoors doesn't sound right to me though, sounds too low. But country to country it can vary as well. The ultimate source for any country-specific RF regulatory info would be that country's government body.