Date: Wed, 17 Apr 2002 19:26:53 +0100 From: "Duncan Barclay" <dmlb@dmlb.org> To: "Marco Molteni" <molter@tin.it>, "John Angelmo" <john@veidit.net> Cc: <freebsd-mobile@FreeBSD.ORG> Subject: Re: 802.11a PCI cards. Message-ID: <01ab01c1e63d$72c9b5e0$27c8a8c0@my.domain> References: <200204160842.g3G8gpA94920@mauibuilt.com><000501c1e583$2d5a8cb0$0300000a@desktop><20020417.093551.83993908.imp@village.org><20020417154100.GL78520@elvis.mu.org><3CBD9E6F.4060909@veidit.net> <20020417171954.40332.qmail@cobweb.example.org>
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> On Wed, 17 Apr 2002 18:10:23 +0200, John Angelmo <john@veidit.net> wrote:
>
> [..]
>
> > I havn't seen a single 802.11a card with support for 802.11b, there are
> > diffrent standard, freq usage and chips.
The standard that will make .11a and .11b cards happen is called .11g. A
primer for those that don't know:
.11b 2.4GHz ISM band, uses direct sequence spread spectrum - 11Mb/s
.11a 5.2GHz ISM band, used othogonal frequency division modulation -
54Mb/s
.11g 2.4GHz ISM band, uses .11b and .11a modulation schemes - 11Mb/s
and 54Mb/s
.11g also has 22Mb/s and 33Mb/s spread spectrum modulations, but these are
optional and are not likely to be widely used. It is likely that some cards
will have it, as the reason it's in the standard is because a big chip
vendor wanted it - usually an indication that they are design silicon.
All standards use the same medium-access controller (MAC) protocols and in
fact the same hardware
(baseband chips) can be made to do both reasonably easily at the design
phase.
As the biggest difference between .11b and .11a is the modulation not the RF
frequency.
A .11g system "only" needs a dual band 2.4GHz/5.2GHz radio front end to be
.11a and .11g. There is
no real point in a .11b/.11g system as .11g is backwards compatible with
.11b.
> > but then again 802.11a isn't allowd in the EU ;)
>
> John,
>
> it's amazing how fast things change...
>
> Philips seems to have made it (802.11a for Europe):
> http://biz.yahoo.com/prnews/020411/sfth045_1.html
.11a for Europe was not allowed until the advent of .11h. .11h adds tramit
power control to .11a, power control is a requirement for use in the 5.2GHz
band in europe. Strictly, the Philips product is .11h.
In the future we will see .11agh systems - I kinda like that.
Atheros, the people who make the chips in the Philips product already have a
.11g chipset. It is likely that Intersil have one too - I don't know whether
they have announced anything officially.
I am also fairly sure that RealTek are developing a .11b chipset - this will
likely bring prices down when they get it working.
Duncan
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