6 Description of the computer program of (n, k) code correcting ability research
6.1 Decoder. For researches the realized programmatic model of Meggitt decoder of cyclic (n, k) code is for n ≤ 32, the block diagram of which is resulted in a figure 3. A Meggitt decoder is a tabular decoder in which entered the following of decoding [8]:
1. Syndrome analyzer includes pre-computing “Table of syndromes” that contains all errors configuration that can be corrected by this (n, k) code and their corresponding syndromes.
2. For the accepted code word a concrete syndrome is calculated by ordinary rule is dividing of the accepted code word on generator polynomial. Calculator syndrome is based on an (n – k)-bit shift register. Syndrome is the remainder of the division.
3. The "Syndrome analyzer" is performed by a search in the tables of the calculated concrete syndrome, reading of errors configuration and presentation of the proper sequence of "1" to "Errors corrector" for the errors correction in the accepted code word.
6.2 Research of correcting ability of (n, k) code. Conducted on a block diagram, resulted in a figure 4.
As a generator of errors symbols is used generator of pseudo noises numbers 0 and 1, in which probability 1 equals probability of error of input symbols р.
Meters fix:
- number of code words which are analyzed in times of supervision – decod_suc, let's designate N;
- number of code word errors at the decoder input – input_err, let's designate Ner. in;
- number of code word errors at the decoder output – output_err, let's designate Ner. out;
- number of decoding fault (the calculated syndrome is not found in tables) – decod_err.
6.3 Order of work with computer program.
1. Measuring of noise immunity is conducted the start of file of meg32n.exe (it is in a folder “Laboratory works of TT-2, laboratory work 4.3).
2. On the requirements of the computer program necessary for work basic data are entered.
3. In the program foreseen also step-by-step mode of operation - parameter /t in a command line and conclusion (seal) of table of syndromes is a parameter /s in a command line.
4. Probability of error can be set, both in an ordinary and in scientific format, for example, 0,025 or 2.5e-2.
Intermediate results indicate on a display each 3 seconds.
7 Requirements to the report
7.1 Name of laboratory work.
7.2 Objectives of laboratory work.
7.3 Results of the home work.
7.4 Block diagram of researches, list of devices (indicators) which are used in LR.
7.5 Results of implementation of items 5.2, 5.3 laboratory task (measured and calculation numerical values etc.).
7.6 Conclusions on every point of laboratory task, in which to give the analysis of the got results is a coincidence of theoretical and experimental information etc.
7.7 Date, signature of student, visa of teacher with an estimation on the 100-mark scale of evaluation.
Lw 4.4 Studying of coding and decoding by error-control convolution codes
1 Objectives
1.1. Studying of convolution codes codecs structure.
1.2. Researching of convolution code control ability.