Re: [Discuss-gnuradio] Project enquiry/interest

[Marcus Müller]

Hi Sajeev,

On 02/23/2015 10:56 AM, Sajeev Manikkoth wrote:
> Hi Marcus,
>
> Thanks again for the detailed explanation of current access technologies. As
> discussed current scheme allows shared access of the channels in time,
> frequency, and space.
Yes, that's how I understood this discussion.
>  What I am talking is about a full simultaneous
> parallel use or access of channel.
I really really don't understand what you mean with that -- what other
dimensions than time, frequency, space (incl. polarization) and code can
you imagine, that would distinguish one electromagnetic wave from another?

>  This is kind of necessity as wireless
> bandwidth demands are ever growing and we are hitting spectrum scarcity.
Spectrum scarcity has been a reality ever since Marconi!
> The
> scheme I am discussing is close to CDMA/MIMO. CDMA base stations already
> differentiate handsets using same frequency with signature sequences.
> Implementing a similar approach on the handset side also to differentiate
> base stations or similar approaches can be in place.
CDMA handsets of course already do CDMA -- otherwise, they wouldn't be
able to communicate with the base station (which would be
disadvantageous, I reckon).
LTE handsets (at least from what I remember about LTE Release 8, which
is the original LTE release) can make use of MIMO. Probably they already do.
>
> In its simplest form the requirement is to allow 2 FM stations using same
> frequency in a location area. And the receivers tune to the station names to
> enjoy different music rather than just to the frequency !
Well, that would then necessarily be some kind of diversification by
coding -- be it CDMA, or be it multiple lower-rate streams embedded in a
broadcast transport stream, which is what DVB does. That doesn't
inherently increase spectrum efficiency -- instead of 100 channels with
bandwidth b, you get 1 channel with bandwidth 100*b, because you can't
cheat channel capacity, and as long as you can't change SNR, the only
thing you can increase to get more information from transmitter to
receiver is to increase bandwidth.
>  Nothing new as a
> concept, limitations to achieve this reasons we have all the existing
> implementations, but 100s of years of engineering fineness. Now this should
> be possible with soft transceivers using today's digital radio techniques
> combined with soft techniques...
What kind of soft techniques? Soft decision decoders?
I still don't really understand where you think that current technology
falls short and what's to improve, but I think I'm getting closer to
understanding exactly what kind of research is of interest to you;
please do elaborate!

Greetings,
Marcus