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

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.

M
>
> 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 <tom@trondeau.com
> <mailto:tom@trondeau.com>> wrote:
>
> On Wed, Jul 30, 2014 at 4:44 AM, Nguyễn Văn Lý
> <lynguyenvan.uet@gmail.com <mailto:lynguyenvan.uet@gmail.com>> 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
>
>
>
>
>
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