From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felix Fietkau Date: Wed, 06 Apr 2011 16:31:37 +0200 Subject: [ath9k-devel] why is bitrate of 65.0 MBit/s MCS 7 appropriate for signal strength of -93 dBm? In-Reply-To: References: Message-ID: <4D9C7949.1050307@openwrt.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ath9k-devel@lists.ath9k.org On 2011-04-06 4:17 PM, Larry Vaden wrote: > On Wed, Apr 6, 2011 at 5:26 AM, Mohammed Shafi wrote: >> On Wed, Apr 6, 2011 at 3:28 PM, Larry Vaden wrote: >>> Mindful that we are all ignorant, just about different things, I ask >>> the ? in the subject line. >>> >>> Would that not influence the success ratio and the performance? >> >> ath9k rate control is based on PER(packet error rate), but previously >> it is based on RSSI. >> But i doubt you are using minstrel rate control, for that please read >> http://wireless.kernel.org/en/developers/Documentation/mac80211/RateControl/minstrel > > With all due respect, I do not think your answer is responsive to the > question and the data presented. > >>> tx packets: 45 >>> tx retries: 308 >>> tx failed: 23 > > Note a FAILURE RATE of 50% and retries ~ 700%. Simple packet/retry/fail counters are completely misleading when it comes to debugging wireless issues. > So, why is 65.0 MBit/s MCS 7 even on the table if rate control is based on PER? Because the assumption that lower rates always work better than higher rates is a bad one to make in a rate control algorithm. > Is it possible that some code other than ath9k is jacking with the > data rates (read: I am ignorant about what protections OpenWrt might > have)? You can find better statistics with much more meaningful output in /sys/kernel/debug/ieee80211/phy0/netdev:wlan0/stations/*/rc_stats - Felix