Re: [Cerowrt-devel] Cerowrt-devel Digest, Vol 37, Issue 24

[David Lang <david@lang.hm>]

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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