On Sat, 20 Dec 2014, Mike O'Dell wrote:
15.9bps/Hz is unlikely to be using simple phase encoding
that sounds more like 64QAM with FEC.
given the chips available these days for DTV, DBS,
and even LTE, that kind of processing is available
off-the-shelf (relatively speaking - compared to
writing your own DSP code).
per the chart at
http://ubcdn.co/media/images/product-features/spectral-efficiency-image.jpg
(part of the link above), they use up to 1024 QAM (although the peak rate is
listed at 64 QAM)
I also wouldn't be surprised if their claim for 15.9bps/hz is the aggregate of
both directions at once.
David Lang
keep in mind that the reason the 2.4 and 5.8 ISM bands
are where they are is specifically because of the ready
absorption of RF at those frequencies. the propagation
is *intended* to be problematic. that said, with
good-enough antennas mounted with sufficient stability
and sufficient power on the TX end and a good enough
noise floor on the RX end, one can push a bunch of bits
pretty far.
Bdale Garbee (of Debian fame) had a 10GHz bent-pipe repeater
up on the mountain above Colo Spgs for quite some time. X-band
Gunnplexers were not hard to come by and retune for the
10GHz ham band. i believe he just FM'ed the Gunnplexer
with the output of a 10Mbps ethernet chip and ran
essentially pure Aloha. X-band dishes are relatively
small and with just a few stations in the area he had fun.
-mo
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