Date: Sun, 4 Dec 2011 13:56:05 +0800 From: Adrian Chadd <adrian@freebsd.org> To: Viet-Ha Pham <hapvbk@yahoo.co.uk> Cc: Freebsd Wireless <freebsd-wireless@freebsd.org> Subject: Re: Rate index for 11 Mbps Message-ID: <CAJ-VmokLBw=JMaCLd=oVY189tMeUE4btHOJ9tMbRwykXve4qhQ@mail.gmail.com> In-Reply-To: <C5FE57A2CF4942A2884B7B305E279CD5@PC> References: <3d4d2d249836fafc6acd885693c02198@webmail.entel.upc.edu> <CAJ-Vmo=1k=oKP-vDUH=BLdyeVzGnQvNmJ6TwGcdQjwpgJWt52w@mail.gmail.com> <4ECFCDAB.1080407@entel.upc.edu> <CAJ-VmokQTpgxMo=gmj0LsYhD6t9mmoHXG_sbhZdFNW5_OSGbmg@mail.gmail.com> <a9d1d8f91deb80a89bed98c1ffdb23fd@webmail.entel.upc.edu> <CAJ-Vmo=P%2BWAArZ1Kidh947yHuftZTBwF=Vx5Kn36-LKtD4grPg@mail.gmail.com> <4ED3B4D1.3020701@entel.upc.edu> <CAJ-Vmo=1KimWWEkV4gqEyFiNQRZTkK8okPBSfnc494iJbtLzsw@mail.gmail.com> <4EDA4BBA.6010203@entel.upc.edu> <CAJ-Vmon7-PdC51nWjW-M-ojuShwG-iNrBpztNovsZpzgjm9BqA@mail.gmail.com> <4EDA609F.2080401@entel.upc.edu> <CAJ-VmomqbBpJ9whQ2EStP7i5fuaKvR=%2BA9gxQJm3hZnCi%2BJnOg@mail.gmail.com> <CAJ-Vmo=hEq9N=FhvdH8Ev7roG3TByJjri3q5rpLPDE__YZ=MZg@mail.gmail.com> <C5FE57A2CF4942A2884B7B305E279CD5@PC>
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On 4 December 2011 13:36, Viet-Ha Pham <hapvbk@yahoo.co.uk> wrote:
> Hi there,
>
> I am working with the rate adaptation algorithm and at the very beginning
> point of testing/programing. I have a concern with the rate index used in
> the HAL.
>
> I wonder if the rate order in the rate table for 802.11g is 1 - 2 - 5.5 - 6
> - 9 - 11 - 12 .... or 1 - 2 - 5.5 - 11 - 6 -9 - 12 ... ?
The order of rate table entries is what you see:
[for 11g]:
/* short ctrl */
/* valid rateCode Preamble dot11Rate Rate */
/* 1 Mb */ { AH_TRUE, CCK, 1000, 0x1b, 0x00, (0x80| 2), 0 },
/* 2 Mb */ { AH_TRUE, CCK, 2000, 0x1a, 0x04, (0x80| 4), 1 },
/* 5.5 Mb */ { AH_TRUE, CCK, 5500, 0x19, 0x04, (0x80|11), 2 },
/* 11 Mb */ { AH_TRUE, CCK, 11000, 0x18, 0x04, (0x80|22), 3 },
/* remove rates 6, 9 from rate ctrl */
/* 6 Mb */ { AH_FALSE, OFDM, 6000, 0x0b, 0x00, 12, 4 },
/* 9 Mb */ { AH_FALSE, OFDM, 9000, 0x0f, 0x00, 18, 4 },
/* 12 Mb */ { AH_TRUE, OFDM, 12000, 0x0a, 0x00, 24, 6 },
..
so it's cck 1, cck 2, cck 5.5, cck 11, ofdm 6, ofdm 9, ofdm 12, ofdm
18 .. ofdm 54.
> I read the source code (ar5212_phy.c) but I am still confused. Also there is
> a comment with the rate table for 802.11g:
>
> /* Venice TODO: roundUpRate() is broken when the rate table does not
> represent rates
> * in increasing order e.g. 5.5, 11, 6, 9.
> * An average rate of 6 Mbps will currently map to 11 Mbps.
> */
I don't know where roundUpRate() is - but yes, if your function tries
to map a throughput to a rate table index, it'll have problems if it
simply finds the first rate greater than your specified bit rate.
HTH,
Adrian
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