Jeff Liebermann wrote:

...
Unfortunately, you're correct. I have considerable experience dealing
with various path impairment issues using various wireless
technologies, especially Wi-Fi. User will complain that they loose
connectivity, drop connections, suffer from erratic performance, and
generally see performance well below what would normally be expected.
The sources are many and varied. They're also very difficult to
identify. Quite a bit can be deduced with simple diagnostics (i.e.
ping stability, MAC layer packet loss, retransmissions) and from
determining the pattern (does it always die during meal times), but in
general, it's way beyond the capabilities of Joe Sixpack. I expect
much of the same with digital TV.

However, I'm not worried much about the RF issues. It will either
work or the customer can get cable or satellite TV. What I'm worried
about are all the added cables and incompatible technologies found on
the back of the HDTV sets and boxes. Another tangle of wires to deal
with.

Anyway, radio is magic. Maybe I should get one of those Halloween
pointed sorcerers hats with the stars and crescents.
http://en.wikipedia.org/wiki/Image:MGM_sorcererhat.jpg


Yep, only buy wireless routers/switches here which allow connection to
"off board" antennas ... (i.e., external antennas)

IMHO, and humble experience, reflections only worsen with a raise in
frequency ... others mileage may vary ... and EVERYTHING you own, which
is metal/conductive, is a wavelength+ at Ghz!

Regards,
JS

On Tue, 16 Sep 2008 17:25:35 -0700, John Smith
wrote:

IMHO, and humble experience, reflections only worsen with a raise in
frequency ... others mileage may vary ... and EVERYTHING you own, which
is metal/conductive, is a wavelength+ at Ghz!

If the US had gone with the DVB-T COFDM standard, instead of the ATSC
8VSB standard, we would have much better immunity to reflections.

OFDM is fairly immune to reflections, which appears as frequency
selective fading. If a few carriers end up cancelling with a
reflection, then COFDM still has 1700 or more carriers that continue
to pass data. With FEC, most of the data gets through. Something
like this:
http://www.navtechsystems.co.uk/services/micro_links/cofdm_dig_theory.html

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
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