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Re: Encode and modulate a test message on GNU Radio 3.8

From: Rodrigo Ruiz
Subject: Re: Encode and modulate a test message on GNU Radio 3.8
Date: Mon, 19 Jul 2021 10:44:30 +0200

Hello, I have been studying about this for a few days.

I've got some questions. 

First, I have thought about how I should get it done. 

I have doubts about how to convert the raw file to symbols. Any advice?

After getting the raw file into symbols, I thought of multiplying this with a signal source to get the waveform with my data (Correct me if I am wrong).

But after this, I don't know if I have to filter the signal before sending it with the LimeSDR or I have to do more things.

Hope you can guide me.

El mié, 14 jul 2021 a las 13:25, Rodrigo Ruiz (<rodri.99.24@gmail.com>) escribió:
Okay Marcus, I thought it would appear on the mailing list as well, my bad.

I am starting to understand how my program is supposed to work.

Binary file --> Symbols --> Waveforms

I have no idea on which blocks do this kind of conversions. Still, I don't have the theoretical basis to understand this.

I will focus on understanding how this works, and then look for the blocks I need.

Best regards,

El mié, 14 jul 2021 a las 13:13, Marcus Müller (<mmueller@gnuradio.org>) escribió:
Hi Rodrigo,

please always have the mailing list in CC: (or directly reply to the mailing list), so
that the others see you didn't get lost :)

On 14.07.21 13:06, Rodrigo Ruiz wrote:
> I will try to explain myself a bit better. I want to send a file using the LimeSDR, but
> first I need to use a NRZ codification or something similar and modulate it.

"Or something similar": yes, you'll need to do something different. NRZ solves zero
problems, and doesn't yield a waveform that can sensibly transmitted and then later
received on its own. This is a bit like you saying "I want to design a car, with a sturdy
shaft where I affix the oxes that draw it":
you're mixing technology that only applies to wired communication with those for wireless
communication. Sure, your car can have oxes, but these oxes will not be drawing the car,
because then it would not be a car. Your car would probably be better without the oxes,
and something else instead.

> After this, I will configure the LimeSDR Tx block to transmit that file to a certain
> frequency.

Ah but an SDR doesn't transmit "files", it transmits discrete-time waveform samples. Your
GNU Radio flowgraph's job is to transform the data in the file into symbols, these into
waveforms, and *then* they can be transmitted.

> Then with another LimeSDR, the idea is to do the opposite process to get the
> original file.

Exactly, so the flow graph at the receiver needs to take the waveform it gets from the
limesdr (which has absolutely no idea of what kind of transmission you have), and analyze
it such that it sees the symbols that your transmitter put into a waveform, and gets the
data bits they corresponded to!

> I will keep studying and let you know about my progress.

Best regards,

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