I recently noticed that Cisco AP 1142 Tx power level is not a constant value. It is dependent on a data rate in use.
Less words, here’s an example of “show controllers dot11Radio” taken from Cisco AIR-LAP1142N-E-K9:
interface Dot11Radio0 Radio AIR-AP1140G, Base Address b4a4.e3ca.f130, BBlock version 0.00, Software version 3.00.81 Serial number: <cut> Number of supported simultaneous BSSID on Dot11Radio0: 16 Carrier Set: EMEA (EU) (-E) Uniform Spreading Required: No Configured Frequency: 2462 MHz Channel 11 Allowed Frequencies: 2412(1) 2417(2) 2422(3) 2427(4) 2432(5) 2437(6) 2442(7) 2447(8) 2452(9) 2457(10) 2462(11) 2467(12) 2472(13) Listen Frequencies: 2412(1) 2417(2) 2422(3) 2427(4) 2432(5) 2437(6) 2442(7) 2447(8) 2452(9) 2457(10) 2462(11) 2467(12) 2472(13) 2484(14) Beacon Flags: 0, Interface Flags 20105, Interface Events 0, Mode 9; Beacons are enabled; Probes are enabled Configured Power: 17 dBm (level 1) Active power levels by rate 1.0 to 11.0 , 16 dBm, changed due to regulatory maximum 6.0 to 48.0 , 13 dBm, changed due to regulatory maximum 54.0 to 54.0 , 11 dBm, changed due to regulatory maximum 6.0-bf to 54.0-b, 10 dBm, changed due to regulatory maximum m0. to m5. , 13 dBm, changed due to regulatory maximum m6. to m6. , 11 dBm, changed due to regulatory maximum m7. to m7. , 10 dBm, changed due to regulatory maximum m8. to m13. , 13 dBm, changed due to regulatory maximum m14. to m14. , 11 dBm, changed due to regulatory maximum m15. to m15. , 10 dBm, changed due to regulatory maximum m0.-4 to m5.-4 , 13 dBm, changed due to regulatory maximum m6.-4 to m6.-4 , 11 dBm, changed due to regulatory maximum m7.-4 to m7.-4 , 10 dBm, changed due to regulatory maximum m8.-4 to m13.-4, 13 dBm, changed due to regulatory maximum m14.-4 to m14.-4, 11 dBm, changed due to regulatory maximum m15.-4 to m15.-4, 10 dBm, changed due to regulatory maximum 6.0-d to 48.0-d, 13 dBm, changed due to regulatory maximum 54.0-d to 54.0-d, 11 dBm, changed due to regulatory maximum OffChnl Power: 16, Rate 1.0 Allowed Power Levels: -1 2 5 8 11 14 17 Allowed Client Power Levels: 2 5 8 11 14 17
Why is it like this? Why higher data rates have lower Tx power levels? These were my questions too. Read more …