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List:       gnuradio-discuss
Subject:    Re: Transmitting on a single subcarrier
From:       Marcus_Müller <mmueller () gnuradio ! org>
Date:       2024-03-18 12:37:17
Message-ID: 67f77c59-7955-4f3a-a5ce-13f481fb88a0 () gnuradio ! org
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Hi Sourya,

On 16.03.24 22:30, Sourya Saha wrote:
> I am using an OFDM transmitter and receiver blocks from GNU radio. Essentially what \
> i want  to do is split up the bandwidth into 64 subcarriers and trasmit on any one \
> of the  subcarriers, say subcarrier 3.

Remark: that is just FSK, but due to the nature of OFDM an FSK with a \
less-than-pretty  symbol shaping, and due to the cyclic prefix, an FSK with a phase \
jump within each symbol.

*Usually*, you'd avoid doing that, and just build an FSK system. Especially, since if \
you  only use one carrier at a time, you lose the ability to sense the channel, or \
use  Schmidl&Cox (or similar methods) for synchronization, so there's no arguments \
going for  OFDM here – that's why I pointed out that OFDM was a rather advanced \
topic, you need to  understand *why* you're using it, fighting *which* channel \
problems. You get all the complexity, the overhead and all the problems of OFDM, \
without any data  rate benefit.

However, nothing in GNU Radio would stop you from doing that:
Data vectors with a lot of zero entries and a single non-zero entry.

> If that is to be done, in the data carriers field of the  ofdm transmitter and \
> receiver, mentioning just '3' as the subcarrier should work.

Not sure what "mentioning" means, but as described above: data vector with all zeros, \
but  a non-zero value in the third entry.


Best,
Marcus


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