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Reed Solomon encoding/decoding for binary data

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I want to encode a binary data with the rsenc. It does the work but it generates random integer parities appenended in the end of the data vector. And when I try to manipulate it with adding random binary values and then pass it through the decoder all the results are messed up. I do get the final result correctly but the rest of the properties are all messed up. Here's one small example of what I did.
message_in_bin_enc = rsenc(message_in_bin_gf,n,k); % example message is [0 0 1] as a galois field.
bin_Rs_enc = message_in_bin_enc;
binRandom = randi([0 1],1,4);
bin_Rs_enc (1,4)= binRandom(1,1);
bin_Rs_enc (1,5)= binRandom(1,2);
bin_Rs_enc (1,6)= binRandom(1,3);
bin_Rs_enc (1,7)= binRandom(1,4);
%So here I tried to manipulate the parity bits with my very own random
%binary bits cause I need the entire data as a binary stream.
% Let's say now the message looks something like [0 0 1 0 0 0 1] assuming
% its a (7,3) RS code.
%Then once it passes through my circuit which (can)randomly flips the
%message bits. e.g : [0 1 0 0 0 0 0] (error)
error = gf(bin_Rs_enc_1,m); % bin_Rs_enc_1 is when it passes through the ciruit and error in introduced.
[corrected_message,sheesh] = rsdec(error,n,k);
%Now if I decode all the results are butchered up for some odd reason tho I
%get the correct final ans.
Please guide me through this. Thank you in advance.

Accepted Answer

Akira Agata
Akira Agata on 14 Jun 2021
Since RS system object has 'BitInput' option, I would recommend using comm.RSEncoder rather than rsenc if you want to evaluate FEC performance for binary sequence. The following is a simple example:
% RS(N,K)
N = 7;
K = 3;
% Create RS(7,3) encoder/decoder object
rsEnc = comm.RSEncoder(...
'BitInput', true,...
'CodewordLength', N,...
'MessageLength', K);
rsDec = comm.RSDecoder(...
'BitInput', true,...
'CodewordLength', N,...
'MessageLength', K);
% Since each symbol of RS(7,3) is element of GF(2^3), RS(7,3) encodes every
% 9 bits (= 3 x 3) and generates RS code word of 21 bits (= 3 x 7) length
% Encode 9 binary data bits and create 21 bits code word
rng('default'); % for reproducability
tx_bin = randi([0 1],9,1);
tx_enc_bin = rsEnc(tx_bin);
% For example, add 1 error at the 3rd bit
rx_bin = tx_enc_bin;
rx_bin(3) = 1;
% Decode the received bits
rx_dec_bin = rsDec(rx_bin);
Just in case, let's confirm that the error was corrected:
>> isequal(tx_bin, rx_dec_bin)
ans =
logical
1
  3 Comments
Das Siddharth
Das Siddharth on 16 Jun 2021
Thank you so much for finding the time to explain this to me. I really appreciate this.

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