[PATCH] hostapd: check for overlapping 20 MHz BSS before starting 20/40 MHz BSS

Jouni Malinen j
Thu May 15 15:40:04 PDT 2014

On Wed, May 14, 2014 at 01:11:44PM +0530, Rajkumar Manoharan wrote:
> Before starting a 20/40 MHz BSS, an 40-MHz-capable HT AP is required by
> the rules defined in IEEE 802.11-2012 10.15.5 to examine the channels of
> the current regulatory domain to determine whether the operation of a
> 20/40 MHz BSS might unfairly interfere with the operation of existing
> 20 MHz BSSs. The AP (or some of its associated HT STAs) is required to scan
> all of the channels of the current regulatory domain in order to ascertain
> the operating channels of any existing 20 MHz BSSs and 20/40 MHz BSSs.
> (IEEE 802.11-2012 S.5.2 Establishing a 20/40 MHz BSS)

Thanks, applied with some modifications. This was too strict and the
commit log did not really identify the exact rule that is used here.
This is verifying that P == OT_i for all i (see The part
that was too strict was in not allowing P == OT_i, i.e., just the fact
of OT_i being non-empty was used to disable 40 MHz. I changed that to
allow P == OT_i, i.e., allow 40 MHz unless there is a 20 MHz channel on
a channel that is not the selected primary operating channel.

Jouni Malinen                                            PGP id EFC895FA

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