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

From: Nguyễn Văn Lý
Subject: Re: [Discuss-gnuradio] What do Packet Encoder and Packet Decoder do?
Date: Wed, 30 Jul 2014 21:14:00 +0700

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.

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 :-)

Thank you so much

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> wrote:
On Wed, Jul 30, 2014 at 4:44 AM, Nguyễn Văn Lý <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


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.


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