MATLAB: Do I receive an error when I use a codeword length greater than 511 in the BCHENC function in the Communications Toolbox 3.1 (R14SP2)

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The documentation of the BCHENC function states that the maximum allowed codeword length, n, is 65535. However, I receive an error when I use a codeword length greater than 511.

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There is an error in the documentation of BCHENC function in the Communications Toolbox 3.1 (R14SP2). It mentions the maximum allowed codeword length, n, is 65535. The maximum allowed codeword length for BCHENC is only 511. However, this limitation has been removed in Communications Toolbox 3.2 (R14SP3) where BCHENC allows the maximum codeword length, n, to be 65535.

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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: Are BER curves for convolutional codes, with code rates other than 1/2, calculated incorrectly using BERTOOL in Communications Toolbox 3.1 (R14SP2)

This bug has been fixed in Release 14 Service Pack 3 (R14SP3). For previous product releases, read below for any possible workarounds:

We have verified that there is a bug in Communications Toolbox 3.1 (R14SP2) in the way that BERTOOL handles convolutional codes with code rate other than 1/2.

There are no known workarounds.

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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: Are BER curves for convolutional codes, with code rates other than 1/2, calculated incorrectly using BERTOOL in Communications Toolbox 3.1 (R14SP2)

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