Sunday, March 27, 2011

11n TX and RX experiments..

My experiments so far are as follows (all in 5GHz mode - 2GHz is just too busy in my apartment complex):
  • FreeBSD <-> FreeBSD 11n is stable on the AR9160 and AR9220. TX aggregation is disabled, so it reaches around 35-40mbit in HT/20 and 45mbit in HT/40 mode. I'm getting MCS13 between an AP and STA which are in different rooms in my apartment. MCS15 is achievable if the units are close to each other.
  • Short-GI in 40MHz works fine.
  • When RX aggregation is enabled, and IEEE80211_AMPDU_AGE is enabled with net.wlan.ampdu_age set to 5 (it defaults to 500), I get ~ 55mbit RX in HT/20 and ~ 75mbit RX in HT/40 mode. There's problems with out of order packets that are appearing -before- the calculated block-ack window and net80211 is dropping those. I'll investigate why at some point.
  • FreeBSD works fine as an 11n AP, obviously with A-MPDU TX disabled.
There's lots of stuff that needs to be tested at this point, including:
  • 2GHz operation, obviously!
  • 11n and legacy co-operation.
  • Other chipsets - AR5416, AR9280, AR9285.
  • Behaviour in the presence of noise, busy channel, etc.
  • Make sure that HT/40 mode is -correctly- protecting frames on both channels and is correctly waiting to make sure both channels are free before transmitting!
And stuff that needs to be implemented before we enable it by default:
  • A-MPDU TX aggregation, for STA, AP, Mesh and adhoc modes - this one is really needed and is going to take some time to do.
  • HT RTS frame protection - I have code for this which I'll commit soon.

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