[RFC v1 0/1] hostapd: Beacon generation with Power Constraint IE - 11h TPC

Srinivasan B srinivasanb
Mon Feb 4 04:12:52 PST 2013

     This design document proposes changes in hostapd to include "Power 
Constraint IE" in beacon.

Main Idea:
Based on the current operation mode (11a) and 80211h flag enabled in 
hostapd.conf, hostapd
supports the following:

1.Power Constraint IE:
Including "Power Constraint IE" in beacon with appropriate value for 
"Local power constraint" helps
the device/AP to be in compliance with 802.11h (part of 11n / wpa2 
interop test specification).

1.1 Ability for an AP to generate beacons/probe response with Power 
Constraint IE:

     * hostapd generates beacons with "Power constraint IE" with value 
for "Local Power Constraint" set to 0dB.

1.2 Reason for setting "Local Power Constraint" as 0db:

     * Section (h)(1) of Electronic Code of Federal Regulations (e-CFR) 
states that TPC mechanism is not
         required for systems with an e.i.r.p. of less than 500 mW. 
U-NII devices operating in
         the 5.25-5.35 GHz band and the 5.47-5.725 GHz band shall employ 
a TPC mechanism.
     * As per FCC standard, for country US, the MAX TX power for UNII-2 
band is 23dB/200mW.
     * As per CRDA, as an example, the Max TX power provided for UNII-2 
band for country US
         is 20dbm/100mW which is below the minimum requirement to start 
     * As per ETSI standard, the MAX TX power for UNII-2 band is 23dB. 
As per CRDA, as an
         example, the MAX TX power for UNII-2 band for country 
     * Since CRDA provides a reduced TX power level, value of 0dB 
provides an opportunity
         for the client devices to operate at Power Limit provided by CRDA
         (Local MAX TX power = regulatory max - power constraint).

Looking forward for suggestions & information.

Thanks & regards,

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