From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nenad Opsenica Date: Wed, 28 Oct 2009 17:04:51 +0100 Subject: [ath9k-devel] Several questions and observations Message-ID: <4AE86BA3.7070200@panline.net> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ath9k-devel@lists.ath9k.org Hi everybody, I would like to ask several questions and write some of my observations regarding ath9k. My testbed consists of two UBNT Routerstation boards with Mikrotik R52N MiniPCI card each, with OpenWRT kamikaze (trunk - r18131). This revision uses kernel 2.6.30.8 (or 2.6.30.9) and compat-wireless-2009-10-09. I'm testing 802.11n connection between AP and STA, both of them are on my desk, few feet apart; one UBNT RS acts as AP, other as STA. Well, here are the questions: - is there any way I could tune some of "advanced" parameters, e.g. slot time, ack timeout, ... etc? - is there any way to force MCS, HT20, HT40, or SG (apart from "ht_capab" hostapd option which, if I understood right, only announces AP capability without forcing it)? - how can one be sure what is TX power after "iwconfig wlan0 txpower XXX", as "iw wlan0 station dump" on other device always reports same signal value ? Is it even possible to change TX power? - what are real-world performances one can expect in communication between ath9k AP and STA with MIMO 2x2? With both UBNT RS devices on my desk I was able to get stable ~90Mbps transfer when using HT20 at 130Mbps rate, and up to 80Mbps (not_so_stable) with HT40 at 270,300Mbps rate (AP patched to force HT40, see observation #2 and https://forum.openwrt.org/viewtopic.php?id=21544) Observations: - after changing AP operating channel with "iwconfig wlan0 channel XXX" STA is no longer able to associate, not even after STA reboot - when hostapd is configured with "ht_capab '[HT40-][SHORT-GI-40][DSSS_CCK-40]'", STA is using HT40 mode for transfer packets to AP, but AP is still using only HT20. - it looks like STA is not willing to automatically reassociate to AP when AP is restarted (in fact, it is enough to do "wifi down; wifi up" on OpenWRT). One have to issue "iwconfig wlan0 essid XXX" to force STA to associate to AP again. This behavior is really annoying. Regards, Nenad