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UNB EE4253 Digital Communications
Department of Electrical and Computer Engineering - University of New Brunswick, Fredericton, NB, Canada
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Convolutional Coder (R=1/3, K=4)

This online tool passes data through this convolutional coder.


For every input bit (D) there are three output bits (XYZ), defining a rate one-third (R=1/3;) encoder. Because output symbols (XYZ) are computed across four bits (the incoming bit and three previous bits) this coder has a constraint length given by K=4. The polynomials [13,15,17] define the [X,Y,Z] XOR connections (in octal).

Trellis Diagram

Input Bits (D)
trellis
Output Symbols (XYZ)

Input Bits:
Discussion | MATLAB

The initial state (CBA) of the flip flops is assumed to be 000. Three zeros are appended to the incoming data to flush the circuit and return to the 000 state at the end.

Can the message be recovered? - Try the Viterbi Decoder with the above encoded message.

Try this same data with different encoders:

R=1/2, K=3R=1/2, K=4R=1/3, K=4

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Thu May 23 09:50:25 ADT 2013
Last Updated: 08 SEP 2011 		Richard Tervo [ tervo@unb.ca ] Back to the course homepage...
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