> De : adrian.ch...@gmail.com [mailto:adrian.ch...@gmail.com] De la part
> de Adrian Chadd
> Envoyé : lundi 29 juillet 2013 21:08
> À : Cedric GROSS
> Cc : freebsd-wireless@freebsd.org
> Objet : Re: Wifi rates
>
> Hi,
>
> So the trick here is that iwn uses the net80211 rate control API for
> doing things.
>
> Look at if_iwn.c for "ratectl". There's a spot in the TX path where it
> calls it to look up the rate.
>
> It then converts that rate to the iwn PLCP format for the given
> transmission rate. You can google "PLCP". Intel has a few extra bits in
> that field for controlling the NIC behaviour. THat bit is straight
> forward.
>
> Anyway - the trick here is that the net80211 rate control (amrr by
> default) is going to be selecting transmission rates. You can see the
> current rate by doing 'ifconfig wlan0 list sta'. Now, if you're running
> -HEAD net80211 / iwn then AMRR knows about 11n and if_iwn will happily
> use it. In the past it was hackier - AMRR didn't know about 11n rates
> and so iwn "faked" things by pretending it was doing non-11n, and then
> translating these to 11n rates. Hopefully you're running -HEAD and this
> is no longer a problem.
>
> So - do an "ifconfig -v wlan0 list sta" to list the station
> negotiation. It looks like it's doing 11ng but its downgraded to 11n.
Right :
[root@Test]/root#ifconfig -v wlan0
wlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
ether 60:36:dd:93:34:56
inet 192.168.1.20 netmask 0xffffff00 broadcast 192.168.1.255
nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
media: IEEE 802.11 Wireless Ethernet MCS mode 11ng
status: associated
ssid WLenine channel 5 (2432 MHz 11g ht/20) bssid 00:24:d4:97:80:20
regdomain 0 country US anywhere -ecm authmode WPA2/802.11i -wps -tsn
privacy ON deftxkey UNDEF
AES-CCM 2:128-bit powersavemode OFF powersavesleep 100 txpower 15
txpowmax 50.0 -dotd rtsthreshold 2346 fragthreshold 2346 bmiss 10
11a ucast NONE mgmt 6 Mb/s mcast 6 Mb/s maxretry 6
11b ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6
11g ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6
turboA ucast NONE mgmt 6 Mb/s mcast 6 Mb/s maxretry 6
turboG ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6
sturbo ucast NONE mgmt 6 Mb/s mcast 6 Mb/s maxretry 6
11na ucast NONE mgmt 12 MCS mcast 12 MCS maxretry 6
11ng ucast NONE mgmt 2 MCS mcast 2 MCS maxretry 6
half ucast NONE mgmt 3 Mb/s mcast 3 Mb/s maxretry 6
quarter ucast NONE mgmt 1 Mb/s mcast 1 Mb/s maxretry 6
scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250
roam:11a rssi 7dBm rate 12 Mb/s
roam:11b rssi 7dBm rate 1 Mb/s
roam:11g rssi 7dBm rate 5 Mb/s
roam:turboA rssi 7dBm rate 12 Mb/s
roam:turboG rssi 7dBm rate 12 Mb/s
roam:sturbo rssi 7dBm rate 12 Mb/s
roam:11na rssi 7dBm MCS 1
roam:11ng rssi 7dBm MCS 1
roam:half rssi 7dBm rate 6 Mb/s
roam:quarter rssi 7dBm rate 3 Mb/s
-pureg protmode CTS ht htcompat ampdu ampdulimit 64k ampdudensity NA
-amsdutx amsdurx shortgi htprotmode RTSCTS -puren -smps -rifs wme
-burst -dwds roaming MANUAL bintval 96
AC_BE cwmin 4 cwmax 10 aifs 3 txopLimit 0 -acm ack
cwmin 4 cwmax 10 aifs 3 txopLimit 0 -acm
AC_BK cwmin 4 cwmax 10 aifs 7 txopLimit 0 -acm ack
cwmin 4 cwmax 10 aifs 7 txopLimit 0 -acm
AC_VI cwmin 3 cwmax 4 aifs 2 txopLimit 94 -acm ack
cwmin 3 cwmax 4 aifs 2 txopLimit 94 -acm
AC_VO cwmin 2 cwmax 3 aifs 2 txopLimit 47 -acm ack
cwmin 2 cwmax 3 aifs 2 txopLimit 47 -acm
groups: wlan
[root@Test]/root#ifconfig -v wlan0 list sta
ADDR AID CHAN RATE RSSI IDLE TXSEQ RXSEQ CAPS FLAG
00:24:d4:97:80:20 2 5 6M 18.5 0 1162 58480 EP AQEHTRS
SSID<WLenine> RATES<B2,B4,B11,
B22,12,18,24,36> DSPARMS<5> ERP<0x4> XRATES<48,72,96,108> RSN<v1 mc:AES-CCMP
uc:AES-CCMP km:8021X-PS
K> HTCAP<cap 0x6c param 0x3 mcsset[0-23,32] extcap 0x0 txbf 0x0 antenna 0x0>
HTINFO<ctl 5, 0,7,0,0 b
asicmcs[]> WME<qosinfo 0x0 BE[aifsn 3 cwmin 4 cwmax 10 txop 0] BK[aifsn 7
cwmin 4 cwmax 10 txop 0] V
O[aifsn 2 cwmin 3 cwmax 4 txop 94] VI[aifsn 2 cwmin 2 cwmax 3 txop 47]>
[root@Test]/root#ifconfig -v wlan0 list chan
Channel 5 : 2432 MHz 11b
Channel 5 : 2432 MHz 11g
Channel 5 : 2432 MHz 11g ht/20
Channel 5 : 2432 MHz 11g ht/40+
Channel 5 : 2432 MHz 11g ht/40-
And the amrr output :
Test kernel: wlan0: [00:24:d4:97:80:20] amrr_node_init: non-11n node
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: nrates=0, initial rate 0
Test kernel: wlan0: [00:24:d4:97:80:20] amrr_node_init: 11n node
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: nrates=16, initial rate 128
Test kernel: wlan0: [00:24:d4:97:80:20] recv auth frame with algorithm 0 seq
2
Test kernel: wlan0: [00:24:d4:97:80:20] amrr_node_init: 11n node
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: nrates=16, initial rate 128
Test kernel: wlan0: link state changed to UP
Test dhclient: New IP Address (wlan0): 192.168.1.20
Test dhclient: New Subnet Mask (wlan0): 255.255.255.0
Test dhclient: New Broadcast Address (wlan0): 192.168.1.255
Test dhclient: New Routers (wlan0): 192.168.1.254
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: current rate 15, txcnt=12,
retrycnt=144
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR decreasing rate 14 (txcnt=12
retrycnt=144)
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: current rate 14, txcnt=12,
retrycnt=192
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR decreasing rate 13 (txcnt=12
retrycnt=192)
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: current rate 13, txcnt=11,
retrycnt=176
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR decreasing rate 12 (txcnt=11
retrycnt=176)
...
And so on until
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: current rate 0, txcnt=11,
retrycnt=176
Test last message repeated 2 times
Test kernel: wlan0: [00:24:d4:97:80:20] AMRR: current rate 0, txcnt=12,
retrycnt=192
What is 'nrates' and 'rate' in start of output ? Is nrates an index in rate
table ?
After the dhclient, I started a ftp file transfer. As you can see rate
decrease to 0 very quickly.
Is the 'current rate' same as initial nrates value ?
I've found this for MCS :
http://www.digitalairwireless.com/wireless-blog/recent/demystifying-modulati
on-and-coding-scheme-index-values.html
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