On 30 July 2013 02:33, Cedric GROSS <c...@cgross.info> wrote:

> [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]>

Right, there's HT elements in there, so it looks likely you properly
negotiated HT.


> 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

That's the initial "I don't know what you are yet" selection.

> 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

Here it negotiated 11n. The initial rate is 0x80, so MCS 0.

> 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

The rate index starts at MCS0.

> 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

And since there's errors at all transmission rates (look at the
retrycnt), it eventually drops you down to 1mb.

> What is 'nrates' and 'rate' in start of output ? Is nrates an index in rate
> table ?

Yes, look in ieee80211_phy.c .

> 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 ?

Nope. The debugging isn't very clear and I should fix it. But it's
starting in the 11n rate table at MCS0 and it's going down very
quickly into the non-11n rates.

> I've found this for MCS :
> http://www.digitalairwireless.com/wireless-blog/recent/demystifying-modulati
> on-and-coding-scheme-index-values.html

MCS is the 11n encoding scheme.

So you're seeing significant transmit retries. That's worth investigating.

(We still have to merge more code into -HEAD though.)



-adrian
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