RFC: more finegrained configuration of 11b/11g rates and modulations

Jouni Malinen jkmaline at cc.hut.fi
Wed Jul 28 23:22:37 EDT 2004


On Thu, Jul 29, 2004 at 01:23:22AM +0300, Denis Vlasenko wrote:

> The proposal is to use ASCII formatted private ioctl:
> 
> iwpriv <iface> set_rate "1,2,5,11 11p,24d"

I sure hope the parser for this does not end up being implemented in
each driver separately.. This should probably get at least some
processing in user space (e.g., iwconfig), even though this would be
somehwat difficult for the wildcard cases if they are "all supported (by
hw) rates".

> Syntax is: two space delimited lists.
> First one defines basic rate set, second one
> lists additional usable rates and is optional.
> 
> I'll call 6,9,12,18,24,36,48,54Mbit/s data rates
> defined in 11g and 11a standards 'g-rates'
> 
> Syntax of lists: either comma separated list of
> rates in Mbit/s, rounded down to integer value
> (translation: 5 == 5.5Mbit/s), a single entry 'a'
> (means 'all rates'), or 'g' == g-rates only
> (rationale: too many of them to list individually).

This may not be enough for all rates. It looks like it would give unique
values for current standard and amendments, although 10 MHz rates in
IEEE 802.11j were close to generating duplicates.. I would recommend
using array of binary numbers in a way that is able to represent at
least all rates described in IEEE 802.11 MIB (126 rates as an octet
string with increments of 500 Kbps from 1 Mbs to 63.5 Mbps).

However, if we want to keep prorietary extensions in mind, this should
not be limited to 127 * 0.5 Mbps.. In addition, some other extensions
use rate less than 1 Mbps, so this would not actually cover all
currently available hardware if that is a goal here..

Calling 6..54 Mbps rates g-rates is somewhat odd taken into account that
IEEE 802.11a introduced these four years before IEEE 802.11g.. 'a' for
all rates is asking for trouble when we have 802.11a...


> P.S. if you happen to have 11g documents, can you
> mail them to me? I need to look closer on 11g/11b
> rates and modulations compatibility...

IEEE 802.11g is over six months old, si it's available from
Get IEEE 802..

http://standards.ieee.org/getieee802/download/802.11g-2003.pdf

In addition, you should add IEEE 802.11j to things to consider since it
adds "half-rates" for 10 MHz channels..

-- 
Jouni Malinen                                            PGP id EFC895FA



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