HT IBSS with wpa_supplicant

Brian Prodoehl bprodoehl
Sat Apr 30 08:50:51 PDT 2011

I have a patch set for wpa_supplicant to support HT IBSS which needs
some work before I'd consider it worthy of submission.  This builds on
the patches for mac80211 that Alexander Simon has been submitting.
Anyways, I have some questions on which 802.11n-related parameters we
should be able to support for IBSS mode.  By "should be able to
support", I mean that from a high level we should be able to support
this, regardless of if it would actually work under the current state
of mac80211.

Do the Access Category settings used in hostapd (wmm_ac_*) make sense
for IBSS mode?  If so, should it just use the locally-configured
wmm_ac_* parameters when sending traffic to a peer?  Obviously these
could be configured differently across all the nodes, and there isn't
really a way to enforce that they be uniform.

I guess I have the same question on the TX queue parameters (tx_queue_data*).

The HT capabilities (ht_capab in hostapd) is something I've already
implemented in my patch set, but by default the driver (ath9k) seems
to be using all the capabilities that are available anyways (aside
from the HT40-/+ hint, which is really just used by wpa_supplicant
directly).  For instance, even if I don't pass the HT capabilities to
the driver, I've verified that when it comes time to transmit it is
still utilizing STBC.  I would expect TX-STBC to be disabled by
default if this comment in the hostapd.conf example is to be believed:
# Tx STBC: [TX-STBC] (disabled if not set)
Is this a bug in the pending HT IBSS implementation in mac80211?  Or
perhaps really a bug in ath9k.  If I'm not telling it to use TX-STBC,
but the hardware supports it, it shouldn't be using it, right?  I
haven't cross-checked that to see if TX STBC is used in AP mode when
hostapd thinks it is not enabled.


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