3 Replies Latest reply on Jun 25, 2015 5:20 AM by ihsanmert

    How to set transmit power for only 802.11b

    ihsanmert

      Hello,

       

      In the EU, the limit is 20 dbm for the transmit power. In our tests, we observed that our module exceeds 20 dbm in the modulation although in g and n there is no problem about the limit with the default tx power. During the tests, we used mfg_test app with the default tx power by typing the command "txpwr1 -1" over the wl tool.

       

      If we set tx power to <15 dbm (e.g., "txpwr1 -d 14") in the modulation b, measured power is acceptable.

       

      So, in our application on the top of WICED SDK, we need to set tx power for 802.11b to meet the regulation and I do not prefer to reduce transmit power in modulation g and modulation n.

       

      Does WICED SDK have a method to change the transmit power for only modulation 802.11b?


      I know the method wiced_set_transmit_power. If I use this method, tx power is decreased for all modulation types.

       

      Thanks for your helps,

        • 1. Re: How to set transmit power for only 802.11b
          HugoFiennes

          You need to modify the nvram file.

           

          11b power is set in qdbm units by the maxp2ga0 line. eg: maxp2ga0=68 sets +17dBm 11b output power. Whether this matches what you see externally will vary (especially radiated), but you can adjust it relative, eg if you want 1dB lower use (68-4)=64.


          The 11g powers are set relative to this, as 0.5dB backoffs per modulation, one nibble per modulation.

          eg: ofdm2gpo=0x44444444

          means all OFDM modulations are backed off 2dB (MSB = fastest, ie 54Mbps, LSB = slowest, ie 6Mbps)


          The 11n powers are set in two 16-bit values, but the concept is the same.

          eg:

          mcs2gpo0=0x4444

          mcs2gpo1=0x6444

          means 65Mbps is backed off 3dB, the others 2dB.


          So to decrease 11b by 1dB but not alter the 11g/11n powers you would use (in this example):


          maxp2ga0=64

          ofdm2gpo=0x22222222

          mcs2gpo0=0x2222

          mcs2gpo1=0x4222


          (ie, overall power down 1dB, all backoffs reduced by 1dB)


          • 2. Re: How to set transmit power for only 802.11b
            grga

            Hello,

            does this answer your question?  Let us know if it works.

            • 3. Re: How to set transmit power for only 802.11b
              ihsanmert

              Hello,

               

              Thank you very much for your response. Our problem seems to be solved by this new nvram file.