2013-01-18 09:07:07

by Srinivasan B

[permalink] [raw]
Subject: [RFC - v1 - design doc] hostapd: Beacon generation with Power Constraint IE - 11h TPC

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 and if the operating channel is within 5.25-5.35 GHz and
5.47-5.725 GHz band hostapd supports the following:

1.Power Constraint:
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 mimimum
requirement to start TPC.
* 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
SWITZERLAND (CH) is 20dB. * 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,