What is difference between OFDM and GFDM?

Discussion in 'Wireless & RF Design' started by runinrainy, Apr 1, 2015.

  1. runinrainy

    Thread Starter New Member

    May 24, 2014
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    Hi,

    I am trying to understand the difference(s) between OFDM (Orthogonal Frequency Division Multiplexing) and GFDM (Generalized Frequency Division Multiplexing) which are used as a multicarrier modulation techniques in wireless communication. As far as I know the OFDM uses the orthogonal subcarriers and the GFDM is with the non-orthogonal subcarriers when designing a transmitter. The GFDM is possibly going to be the modulation technique for 5G systems as it has been discussed in a research area.

    Could anyone please explain further about GFDM design and its differences from OFDM? What is the purpose of using GFDM when designing a transmitter? The subcarriers are created just after the IFFT?

    In GFDM, how does the IFFT block work when creating the subcarriers?

    What about the subcarrier pulse shaping in GFDM?

    Thanks in Advance!
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    We're hobbyists, not researchers at the bleeding edge of technology. Even if we knew we probably couldn't talk about it because of restrictive agreements we signed as a condition of employment.
     
  3. BR-549

    Well-Known Member

    Sep 22, 2013
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    There certainly is enough material online about it.
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    It's not clear if the TS/OP has surveyed the online material or not. That might be why he is asking here.
     
  5. seanstevens

    Member

    Sep 22, 2009
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    I would have thought its an electronics related question, asked in an electronics forum where people can ask and exchange ideas. If anyone knows about the subject or can talk about it, will, and if they cant they just dont have to answer. I cannot see why the person asking the question should get shut down with an answer like that.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    @seanstevens The problem with that approach, is that in the absence of any response they bump their own threads and complain that nobody is paying any attention to them. I think it is important to set expectations and not try to sell ourselves as something we are not. We do much the same thing in the Homework Help section where we patiently explain that "help" is not the same thing as homework done for you. I don't see it as a case of shutting people down, but rather being honest with them. Then there are the banned topics that are in violation of the TOS. People get shut down and shut down hard, often with bitter complaints. The response is quite simply that the owners get to make the rules and this is not a democracy. That is just the way the world works and I'm sorry it doesn't correspond to you rosy view of how it should work.
     
  7. seanstevens

    Member

    Sep 22, 2009
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    I understand and appreciate what you say with regards to not doing people's home work or their research, which everyone should before posting. I also understand now re bumping and complaining, in my 'rosy' world there is no bumping ever, never have done never will as it is an open forum, people read when they want and answer if they know the answer, if they want to share etc. - no one is forced to answer. From what I see democracy is a bit of a myth, so let the rulers rule!
     
  8. WBahn

    Moderator

    Mar 31, 2012
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    My understanding -- and it is a very superficial and possibly completely off-base understanding -- is that OFDM has some strong advantages particularly when it comes to things like intersymbol interference and interchannel interference because the channel spaces are carefully placed at the nulls of other channels. But this only works well if the transmitters are either rigidly defined or can work together within a predefined frequency plan. For cognitive or adaptive radio where a transmitter wants to exploit unused space in the spectrum, OFDM isn't a good match because it isn't flexible enough. GFDM is simply a more flexible version of OFDM in which the parameters can be adapted independent of a pre-defined spectrum usage plan.
     
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