henry999@eircom.net (Henry) hath wroth:

>Finalisation of 802.11n is still reportedly over a year away.

Actually, the slipping schedule seems to be a continuously moving
target that always seems to remain a year or two away. The current
guess is Dec 2009 for the grand finale, and about July 2009 (my guess)
for something that can be updated to whatever is approved.
http://grouper.ieee.org/groups/802/1..._Timelines.htm

>There is
>of course no guarantee (actually, little likelihood) that any of the
>draft-n gear available now will be upgradable to the standard, when it
>comes.

Well, Dec 2009 is a bit less than 2 years away. Anything you buy
today will probably be obsolete by then. It's not just the MIMO part
that will change in the next two years. Router and wireless features
will also improve. For example, dual SSID's for "guest" WLAN's. Built
in intrusion detection.

>The conventional wisdom for using draft-n equipment at the moment is to
>get all the pieces from the same manufacturer, to make sure they work
>together as intended. But that's not always possible.

Nope. All the same chipsets from the same manufacturer. There's no
guarantee that even a single manufacturers stuff will talk to other
products made with another vendors chips.

Incidentally, the spec includes provisions for two radically different
forms of MIMO. Spacial multiplexing and beam forming are totally
incompatible.

>Have any of the computer or networking magazines, or any of the
>consumer-protection testing labs, run any studies comparing how well (or
>how poorly) 'mixed' environment networks run?

Sorta. This one is several years old:
<http://www.smallnetbuilder.com/content/view/24214/96/>
and doesn't really do any interoperability testing. Some of the
reviews on this site test performance with compatible MIMO and
ordinary wireless clients. I haven't seen any Interop style bake off
testing yet.

>Things like 'The A pcmcia
>card works with B's router but not C's access point, while D's pci
>adapter works with routers from A and C but not B', etc., etc.
>
>Given that there are only, what?, four or five or six major
>manufacturers of consumer- and SOHO-level equipment, it shouldn't be too
>hard to put the more popular models through their paces.

Yep. However, new MIMO models come and go at an alarming rate.
Product lifetimes seem to be about 6 months. By the time the tests
are organized, run, reported, and published, all the products tested
will be obsolete. However, that's not why nobody is doing such tests.
It's because many of the claims presented by MIMO proponents are
unsupportable and all too easily proven to be baloney. Nobody wants
to sponsor a comparative test that demonstrates that MIMO is about
speed, not range.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558