Acquaintance to computer model of decoder.

For this run MatLab, using the icon on the desktop, and then at the command row write block_encoding and press Enter. Master the technique of correcting ability of (n, k) block code researching, i.e. entering of input data, run programs, read the results. Model of the laboratory work is shown in Fig. 7 and 8.

5.2 Charting functions р _out = f (р _in) and р _out = f (E _b /N ₀) without ECC. To this set transmission system mode «without code». Other settings should be following: «Without interleaving», «BPSK» modulation, «AWGN» channel. Change signal/noise ratio from 2 to 9 dB in 1 dB, each time click «To transmit» and at the same time the results of each measurement add to «Archive of measurements». Dependencies р _out = f (р _in) and р _out = f (E _b /N ₀) will be automatically displayed on the scoreboard. Message length L must be set within 10⁵…10⁷.

5.3 Experimental research of correcting ability of the Hamming decoder. Choose the type of code «Hamming». Length code words set from the homework. Change option «Series of measurements» in boxes «Simulation result» and «Archive of measurements». Then repeat the measurement of s.5.2.

Set p _all according to the homework. Using markers measure signal/noise ratio at transmission system «Without code» and with «Hamming» code. Write down the value of CG.

5.4 Experimental research of correcting ability of the BCH decoder. Choose the type of code «BCH» and according to the homework set the parameters of (n, k) code. Change option «Series of measurements» in boxes «Simulation result» and «Archive of measurements». Then repeat the measurement of s.5.2.

Set p _all according to the homework. Using markers measure signal/noise ratio at transmission system «Without code» and with «BCH» code. Write value of CG. Compare the dependence with calculated in homework. Make conclusion about correctness of calculations at home. Draw the dependences of the symbols error probability on the decoder output р _out from the error probability on its input р _in, i.e. р _out = f (р _in), and dependence of the symbols error probability on the decoder output from signal/noise ratio р _out = f (E _b /N ₀) on the same graphs. Each graph must be no less than one page in the workbook.

5.5 Research of properties of correcting codes. Compare the values of CG in ss.5.3 and 5.4, make corresponding conclusions. Change the parameter p _all and conclude on the value of coding gain changes. Change parameters of the code without changing the code rate. Make corresponding conclusions. Change the code rate by changing one of the code parameters. Make CG measurements for the four code rates. According to the results of measurements build a dependence of CG on the code rate for error-control BCH code.

6 Short description of the computer program for (n, k) code correcting ability researching

The model is made in the MatLab environment. Model allows you to change settings of all blocks of transmission system. Message length L is unlimited. Codec can be not used or chosen from three options: Hamming code, BCH code or Reed-Solomon code. Interleaver can also be not used or chosen block matrix interleaver (X,Y). In model you can change the modulation method and levels of the modulated signal. Communication channel with additive white Gaussian noise (AWGN) with constant parameters or fading can be used. Signal/noise ratio varies from 2dB to 9dB.

Model allows you to build graphic of dependence of symbols error probability on the decoder output р _out from the error probability on its input р _in, i.e. р _out = f (р _in), and dependence of symbols error probability on the decoder output from signal/noise ratio р _out = f (E _b /N ₀). Using markers one can calculate the coding gain at allowable error probability on the decoder output р _all. N ­is number of error symbols at the decoder output.

Figure 7 – Block diagram of error-control code ability researching

Дата добавления: 2015-10-31