MATLAB: In Communications Toolbox 3.0.1 (R14SP1), can I determine the number of errors that VITDEC corrected

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I am using a Viterbi decoder from Communications Toolbox 3.0.1 (R14SP1) and would like to know the number of errors the decoder corrected, perhaps as a return argument from the function.

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The ability to determine the number of errors VITDEC corrected is not available in the Communications Toolbox. To work around this issue, you can use BITERR if you have a priori knowledge of the sequence. Given the original sequence and the decoded sequence, BITERR returns the number of differences between the two sequences.

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MATLAB: How to use erasure information to do Reed Solomon decoding with the Communications Toolbox 4.1 (R2008a)

This change has been incorporated into the documentation in Release 2009a (R2009a). For previous releases, read below for any additional information.

The ability to use erasure information with the RSDEC function is not available in Communications Toolbox.

To work around this limitation, you can use the FEC.RSDEC decoder object from the Communications Toolbox, instead of the RSDEC function. The following example demonstrates how this object can be used with erasure information, with m = 3, k = 5, n = 7:

          %%Code parameters
          n = 7; k = 5;
          %%Construct encoder
          coder = fec.rsenc(n,k);
          %%Message to encode
          msg = [0 1 2 3 4]'
          %%Perform Coding
          code = encode(coder,msg)
          %%Construct decoder from encoder
          decoder = fec.rsdec(coder);
          %%Introduce 2 errors in the codeword
          code(end) = 1;
          code(end-1) = 0;
          %%Generate a vector of erasures-- 0 marks a good symbol, 1 marks an error location
          erasures = [0 0 0 0 0 1 1]';
          %%Decode the code without supplying the erasures

          %  Note that the decoded message is incorrect, because the number
          %  of errors (2) exceeds the correction capability (n-k)/2 = 1
          [decoded,cnumerr,ccode] = decode(decoder,code);
          decoded
          %%Decode the code without supplying the erasures
          %  Note that the decoded message is correct now
          [decoded_with_erasures,cnumerr,ccode] = decode(decoder,code,erasures);
          decoded_with_erasures

More details on the FEC.RSDEC object are available at the following link:

 <http://www.mathworks.com/access/helpdesk/help/toolbox/comm/ref/fec.rsdec.html>

Furthermore, if you have the Communications Blockset (a Simulink block library), you can also perform Reed Solomon decoding with erasure information in the Simulink environment. Examples are provided at the following documentation link:

 <http://www.mathworks.com/access/helpdesk/help/toolbox/commblks/ug/fp74297.html#brb6prx>

MATLAB: Is the “Relationship Between Es/No and SNR” in the “Describing the Noise Level of an AWGN Channel” section of Communications Toolbox 3.0.1 (R14SP1) documentation correct

This change has been incorporated into the documentation in Release 14 Service Pack 3 (R14SP3). For previous releases, read below for any additional information:

This has been verified as an error within the documentation for Communications Toolbox 3.0.1 (R14SP1) within the Describing the Noise Level of an AWGN Channel section.

The documentation should read as follows:

Es / No (dB) = 10log10 (0.5 * Tsym / Tsamp) + SNR (dB) for real input signals.

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Related Solutions

MATLAB: How to use erasure information to do Reed Solomon decoding with the Communications Toolbox 4.1 (R2008a)

MATLAB: Is the “Relationship Between Es/No and SNR” in the “Describing the Noise Level of an AWGN Channel” section of Communications Toolbox 3.0.1 (R14SP1) documentation correct

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