Description of laboratory model. Laboratory work is executed on a computer in the HP VEE environment with using a virtual model, the block diagram of which is resulted on the figure 2

Laboratory work is executed on a computer in the HP VEE environment with using a virtual model, the block diagram of which is resulted on the figure 2. A model is intended for cyclic codes: (7, 4), (10, 5), (10, 6), (11, 7), (12, 8), (13, 9), (14, 10), (15, 11), encoding and decoding processes research.

A model allows research consistently encoding, transmission by a telecommunication channel and decoding. It contains the marked by a red color options which a student must set. The blue color windows are used for the model work results indication.

Coder forms the permitted code word by the r = n – k checking symbols calculation and add to them information symbols. The got code word is indicated on the encoder output.

For the transmission by a telecommunication channel implementation it is necessary to enter errors word, length п, consisting of 1 and 0. The symbol 1 is set in those positions, which an error at the transmission by a telecommunication channel must be in. In a telecommunication channel code word from encoder is added with combination of errors by XOR. The got code word is indicated on the telecommunication channel output.

A decoder divides code word on his input, on a generate polynomial. A window under a decoder shows the code word syndrome (in binary presentation); a window left shows the decoder decision about the error symbol number (all codes researched in a model allow to correct single errors).

If a syndrome is zero, a decoder gives message "No errors". If a syndrome is not zero, on the syndromes table a decoder determines the error symbol number and "Error in х^р " message, where р is error symbol number.

The syndromes table contains only п syndromes which correspond to п symbols of the decoded code word. The possible syndromes number is equal 2 ^{n – k} . If n < 2 ^{n – k} – 1, a syndrome which is absent in the syndromes table can appear in a decoder. In this case a decoder gives out the message "Unknown error".

If a decoder defined the error symbol number it gives out the message "Error in х^р ", it corrects this symbol and takes away n – k last symbols. If syndrome is zero or it is absent in the syndromes table, a decoder only takes away n – k last symbols. The information code word appear on the decoder output.