Number of variant for the course work should correspond to the number of a student surname in the group register.

“CHOICE of ERROR-CONTROL CODE And coding gain CALCULATION”

It is given:

- a type of continuous communication channel is a channel with constant parameters and additive white Gaussian noise;

- a method of modulation in the communication channel;

- an allowable bit error probability at the output of error-control code decoder р_all;

- a required coding gain (CG).

It is necessary:

1.To draw the block diagram of the digital transmission system (DTS) including error-control code encoder and decoder, explain function of separate blocks.

2. To give the definition of coding gain. To choose and explain your choice of code parameters, providing necessary CG: code length n, number of information symbols k and order of corrected errors q_c.

3. To calculate the dependence of bit error probability at the output of decoder from the signal-to-noise ratio on the input of demodulator р_d = f₂( ) with usage of chosen code, draw this dependence on the graph from first part of course work. To define the signal-to-noise ratio at the input of demodulator at which allowable probability of bit error р_all is provided in a case of transmission with error-control code. To define obtained CG and compare it with required CG.

The results of calculations show as on fig. 1.

 

4. To calculate the necessary bandwidth of communication channel F_ch, for signal transmission at the given modulation method and error-control code. To make conclusions about “exchange” of necessary signal-to-noise ratio on the necessary channel bandwidth comparing three transmission methods: QPSK, given modulation type, given modulation type and error-control code.

5. To calculate a channel capacity С for two variants of transmission (given modulation type with and without of error-control coding) and compare this values with digital signal rate R.

6. To calculate the coefficients of information h, frequency g and energy b efficiencies for two considered variants of transmission.

7. To build the graph of Shannon limit b = f (g) and compare efficiency of two variants of transmission with each other and with Shannon limit.

8.Conclusions to the course work.List the main results of calculations. Specify advantages and disadvantages of the considered variants of transmission. Which of considered variants of transmission, on your opinion, is preferably to use in the real transmission system? Explain your choice.