Re: [Discuss-gnuradio] Project enquiry/interest

[Sajeev Manikkoth]

Hi Marcus,

Sorry that I did not made my point clear. To conclude this thread, I was
looking for projects and people who think and work following topic is a
realizable goal.

Radios which transmit and receive without interference worries (co-channel,
adjacent channel, etc) by overcoming the hardware and radiator limitations
with software algorithms. Perhaps with new hardware techniques too. 

Regards,
Sajeev

-----Original Message-----
From: Marcus Müller [mailto:address@hidden 
Sent: 24 February 2015 19:15
To: Sajeev Manikkoth; GNURadio Discussion List
Subject: Re: [Discuss-gnuradio] Project enquiry/interest

Hi Sajeev,

the problem is that there are so many projects that you'll find when you
use google with '<TOPIC> "GNU Radio"', that it's very hard to know what
you're looking for -- notice how you still say

"my references on this topic"

whilst I'm still totally confused what your topic actually is. I've talked
to some other people and they don't think you've made it clear what your
talking about, either. 

You should really, really find the technical terms, the jargon, that
describes what you're looking for, and then it will be easy for us to
recommend something. Up until now, I feel you've been extremely vague -- and
yet you make it all sound so interesting :)

Greetings,
Marcus

On 02/24/2015 02:35 PM, Sajeev Manikkoth wrote:
> Hi Marcus,
>
> I understand this thread need to end, as the members of the list are
silent
> except your very informative descriptions. I could get few points to dig
> further upon for my references on this topic. But I was excepting to get
> some project references people are working on this or similar topics with
> GNU radio, where in I can involve and pursue my research interests. Any
ways
> I will follow the topics under discussion in this list and step in as and
> when I see something interesting.
>
> Once again thank you very much...
>
> Best regards,
> Sajeev
>
> -----Original Message-----
> From: Marcus Müller [mailto:address@hidden 
> Sent: 24 February 2015 13:51
> To: Sajeev Manikkoth; address@hidden
> Subject: Re: [Discuss-gnuradio] Project enquiry/interest
>
> Hi Sajeev,
>
> thanks for adding more information!
>
> There's two things I'd like to mention at this point; after that, I
> think it might be a good idea to let this discussion thread die. I feel
> I'm digressing too much, and it'll be easier for you to come up with a
> new email that says "Hey, do you know research on XY, possibly related
> to GNU Radio", now that we have mentioned so many concepts with names,
> and you can pick one or a few XYs from these. Bombarding you with more
> terms really won't help either of us, I guess :)
>
> So these two things are 1. quantifying your ideas, and 2. cognitive
> communications:
>
> 1. telecommunication with electromagnetic waves is not very much like
> looking at objects with the human eye, I agree.
> But that's basically because the sensory apparati involved are so
> different: The eye is a focussable matrix detector for photons, which
> means you kind of get a whole set of per-frequency-bin intensities at
> once, whereas digital communication usually needs to rely on a single
> (or a few) antennas receiving a signal, which only has a single quality
> -- voltage over time.
> Thus, your comparison kind of needs to take a step back: First of all,
> you'd need to make some kind of "image" out of the temporal signal,
> before you can do anything cognitive on it. In fact, projecting a
> received signal into a vector space is a method very common to almost
> all digital transmission systems:
> RF engineers of think of signals as combination of points in a
> N-dimensional room, constructed by base vectors of independent vectors,
> just like a 2D image might be constructed by mapping colors to points in
> the plane.
> The art of finding appropriate signal representations has led to a whole
> lot of different transmission schemes, some of which are
> constellation/pulse shape based (think of a PSK with a matched filter),
> some employ orthogonality of specific frequency components to first map
> a set of symbols to a time signal (OFDM), some simply represent
> different symbols/users by different sequences of chips (CDMA);
> detectors for these different representations use the characteristics of
> the signal model to optimize correct decoding. "Optimize" is a hard
> word, here: It demands that the signal model is somewhat mathematical,
> which allows the engineer to find an *optimal* decoder, in many cases.
>
> After that, there's the art of channel coding (as opposed to source
> coding, and largely unrelated to CDMA), which approaches the actual
> information to be sent from a information theoretical point of view; it
> adds redundancy at the transmitter to make it easier for the receiver to
> correctly decode what has been sent, and it gives the receiver
> appropriate methods to maximize probability of correct decoding. Network
> Coding is somewhat related to this, and is yet another discipline of
> communications engineering you should have a look at.
> Again, there's a *large* mathematical background to this, and a lot of
> things have upper bounds for how well things can possibly work, there
> are solutions to specific cases that are proven mathematically to be the
> optimum, and there are lots of research to be done -- most of the codes
> we know today are rather bad compared to what we know must exist, but
> science has not been able to find better ones, so far[1].
>
> Somewhere in between the mapping of physical quantities to code words,
> and finding good codes to encode information, to maximize
> speed/reliability/spectrum efficiency of transmission [2], or somewhere
> across, sits equalizing. Now, equalizers have a lot of properties that
> people consider "smart", "adaptive", and thus somewhat "cognitive", but
> that brings me to my second issue
>
> 2. "cognition" is one of the buzzwords of RF communication of the last
> 15 years, thanks to Mitola '98, who coined the term "cognitive radio",
> to describe systems that are aware of their RF environment and act based
> on this awareness. This comes with a whole lot of theory on what a radio
> must/can/could know, how to exchange that kind of info etc. Network
> coding once again comes into play -- you should definitely have a look
> at that.
>
> Now, I'm not totally sure you're going after cognitive radio -- from
> what you describe, designing a good channel code that reaches the
> channel capacity[3], maybe combined with an equalizer, fits what you're
> looking for, which is recognizing advanced patterns in a
> more-than-1-dimensional representation of the signal. There's a lot of
> approaches that do this -- chose the one you want to dig deeper into :)
> Computer vision is a fairly mature field of research, and it has led to
> a lot of signal models for 2D images; all the things I said about
> mathematical optimization above apply to these models, too, and the
> point here is that it's always crucial to find a good representation
> (ie. a well-fitting model) that explains the signal to your detection
> algorithm.
>
> There are a lot of decoder classes that are what one could call learning
> -- iterative methods that use the information gathered in the last
> processing step to aid and improve the next step -- be it a definite
> decision about the (N-1)th bit employed to calculate the likelihoods of
> the Nth bit, or be it a soft decision state used in a iterative decoder
> arbitrary times. Have a look at Turbo Decoders -- they interleave
> decoding and equalizing, and thus learn from symbols of the past to
> interpret the coming symbols more accurately.
>
> So, to conclude: 1. you say you want to see things being done better,
> but you'll need to mathematically define "better"; in many cases, the
> structures employed are mathematically proven to be optimal, and 2.
> you're comparison to recognition of things by the human eye needs to
> first find a mathematical model that makes an image from the signal, and
> for which you can be smarter than the solutions that are already known.
>
> Best regards,
> Marcus
>
>
>
> [1] which, to me, was one of the core things I took away from my channel
> coding course.
> [2] Note that I use these three different goals as one thing here -- you
> can often do this, because the common problem is "for this given
> channel, how can we get a maximum of bits across", and a good solution
> solves all the three problems.
> [3] Wow, my footnotes are getting channel coding centered these days.
> Reaching channel capacity means: No matter what you do, for the SNR in
> this channel you can't get more bits across (with arbitrarily little
> error) than possible with this code.
>
> On 02/23/2015 06:02 PM, Sajeev Manikkoth wrote:
>> Thanks Marcus, and adding some more details. Current signal detection
>> mechanisms for years totally rely on signal attributes (frequency,
timing,
>> amplitude) for differentiation of signals. Cognitive detection mechanisms
>> and new PHY layer techniques which emulate human eye like detection and
>> differentiation need to be developed. One simple scheme I can think of
is:
>>
>> Human eye can differentiate 2 similar items or let us say identical
twins.
>> And when we find it difficult, we add different identification marks on
>> those twins to differentiate and identify. In a similar fashion may be a
>> transmitter can add a unique identification while
modulating/transmitting,
>> and the receivers can look for those. Receivers shall first tune to the
>> channel frequency, and then to the unique transmission id to latch to the
>> desired transmitter.
>>
>> In general my interest was to see interest and projects which develops
>> cognitive detection mechanisms and associated new PHY and MAC layer
>> techniques. Hope I am making some sense now...
>>
>> Best regards,
>> Sajeev 
>>
>> -----Original Message-----
>> From: Marcus Müller [mailto:address@hidden 
>> Sent: 23 February 2015 19:55
>> To: Sajeev Manikkoth; address@hidden
>> Subject: Re: [Discuss-gnuradio] Project enquiry/interest
>>
>> 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
>>