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Re: [Discuss-gnuradio] What do Packet Encoder and Packet Decoder do?

From: Martin Braun
Subject: Re: [Discuss-gnuradio] What do Packet Encoder and Packet Decoder do?
Date: Wed, 30 Jul 2014 16:19:24 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0

On 07/30/2014 04:14 PM, Nguyễn Văn Lý wrote:
> Thank you Tom,
> I found a note in documentation of the *Packet Encoder *block** where it
> declares that the *Packet Encoder* is for use with the gnuradio
> modulator blocks: GMSK, DPSK, QAM. I don't know why only these modulator
> blocks are supported, but not some popular things like BPSK or QPSK.
> Another thing is that my task requires the use of OFDM.

These should also work (they are basically subsets of QAM), but *you*
have to make sure the absolute phase is correct *before* going into the
packet decoder.

> Suppose now I have a simple flow graph as below:
> File Source -------> Packet Encoder -------> Packet Decoder --------->
> File Sink
> I wonder what types of file can be loaded and processed properly in the
> *File Source* block (text, image, or video ...), and the same question
> for the *File Sink* block :-)

Any file. The packet blocks really don't care about the contents.

> Thank you so much
> Van-Ly
> Van-Ly Nguyen,
> Signals and Systems of Laboratory - SSL  
> Faculty of Electronics and Telecommunications - FET         
> University of Engineering and Technology - UET      
> Vietnam National University, Hanoi - VNU  
> Tel: (+84) 978 819 406
> On Wed, Jul 30, 2014 at 8:24 PM, Tom Rondeau <address@hidden
> <mailto:address@hidden>> wrote:
>     On Wed, Jul 30, 2014 at 4:44 AM, Nguyễn Văn Lý
>     <address@hidden <mailto:address@hidden>> wrote:
>         Hi all,
>         Can anyone tell me what do *Packet Encoder* and *Packet Decoder*
>         blocks do? and it would be great if you can give me some example
>         :-) 
>         Thanks in advance
>         Van-Ly
>     These are very simple example blocks to show you how to packetize
>     data. Packet bytes go in, they get wrapped into a packet of a given
>     payload length with a header, access code, and preamble. The header
>     is just a 2x repetition of the payload length (16 bits for each
>     field). Leaving the preamble and access code blank just chooses the
>     defaults.
>     The decoder just looks for the access code with the number of
>     available bits wrong. When it's found, it reads the header to get
>     the payload length, extracts the payload, and outputs the payload.
>     Hope this helps.
>     Tom
> _______________________________________________
> Discuss-gnuradio mailing list
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