This example uses ADS in digital signal processing to simulate a simple communication system.The ystem consists of a random binary source,modulater (in this example NRZ), Additive White Gaussian Noise Channel, and a reciver. then the same system was simulated after using channel coding by adding a convolutional encoder and a viterbi decoder. the simulation results show how channel coding reduces errors in the system and still uses less energy.

Here is a list of the components used in this example:

1- Binary random bits output (common components library)

This component generates output binary bits with bit probability defined by probability of zero and this can be in the range of 0 to 1. By double clicking on the component in the schematic you get a window where you can change the parameters of this component, which is here bit probability.

2- Logic to NRZ block (signal converters library)

This component converts the logic level to NRZ level. In this example logic '1' is encoded into -1 and logic '0' is encoded into 1.

3- Bit-By-Bit convolutional encoder (CDMA channel codes library)

The encoder type in this example is (1/2 K 3 g0 05 g1 07). The rate is 1/2 The constraint length is 3 g0 (05=101) gives the polynomial of the first modulo 2 adder g1 (07=111) gives the polynomial of the second modulo 2 adder.

4- Delay component (Numeric, control library)

This component delays the input from output by N samples.

5- AWGN channel (CDMA test library)

Additive white Gaussian noise channel, in this component the noise of the channel can be controlled by changing the parameter EbN0 Ratio.

6- Bit-By-Bit Viterbi decoder for convolutional encoder (CDMA channel codes library)

The decoder uses the same parameters as the encoder (1/2 K 3 g0 05 g1 07). For more information about Viterbi decoder check to the following link: http://pweb.netcom.com/~chip.f/Viterbi.html

7- TKPlot (interactive control and display library)

Displays the input versus sample number.

8- DF, DataFlow (controllers library)

This controller is required for signal processing simulation.