Regarding demodulation in ofdm

sir,
i am new to gnc and i am doing a project on ofdm implementation
using gnu radio.i am fine with modulation part but got stuck with
demodulation.i am requesting you to plz help me in doing demodulation.i
am
attaching block diagram of demodulation circuit.

thank you.

Hi Roja,

you forgot to actually explain what does not work. I’ll refer you to [1]

there’s a few things odd with your flow graph, nevertheless:

  1. Double throttle: you’ll only ever need one throttle block. I’d
    explain, but I think it’s easy enough to understand once one realizes
    what throttle does.
  2. You want to send binary data, but you convert that to float before
    passing it to OFDM mod. I’m pretty sure that’s not what you really want
    to do – just set the input type in the OFDM mod block to byte, short or
    int, and generate random numbers between 0 and 2^8, 2^16 or 2^32,
    respectively, using the corresponding output type of your random source.
  3. This is really just nitpicking, but I assume you’re a student and
    this won’t be the last time you ask someone else for help: Please rotate
    all your blocks so that one can read them, and they don’t overlap, try
    to align them and place them logically sound etc., when sharing.
    It doesn’t take much effort with the current versions of GNU Radio
    Companion, and it gives the people you ask the feeling that you already
    went through “tidying up” and don’t force them to do that mentally.
    Actually, there’s another feature in GRC that makes taking nice
    screenshots easier: Under “File” you’ll find “Screen Capture”, which
    will give you a correctly-sized image of only your flow graph, not the
    whole desktop.

If you’re asking about the warning you see in the console window: it’s
exactly that, a warning, not an error. It means GNU Radio had to
allocate a bit more of buffer, but it doesn’t impact the functionality
of your flow graph.

Greetings, and happy hacking :slight_smile:
Marcus

[1]http://gnuradio.org/redmine/projects/gnuradio/wiki/ReportingErrors

On 03/05/2015 07:03 AM, roja yadav wrote:

sir,
PS: there are ladies in here, too. If I’m new to a mailing list, I
usually start greeting by “Hello,”, or something like “Dear XY
community,”, until I get a feeling how people respond.

   i am new to gnc

I think you mean GRC, _G_NU _R_adio _C_ompanion.

and i am doing a project on ofdm implementation using gnu radio.i am
fine with modulation part but got stuck with demodulation.i am
requesting you to plz help me in doing demodulation.i am attaching
block diagram of demodulation circuit.
That’s a flow graph, not a circuit. Circuit is only used for electronic
circuits (with capacitors, resistors, stuff like that); in GNU Radio,
you actually can’t have cycles in your flow graph, making this even less
a circuit (just in case you need to write a report later on :wink: ).

Also, you’re using the old-style OFDM blocks. I suggest looking at
ofdm_loopback.grc for an example on how to use the new ones.

M

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