Plot Noisy 16-APSK Constellation

Apply 16-APSK modulation to a signal of random data. Pass the modulated signal through an AWGN channel. Plot the signal constellation.

Use the Open model button to open the slex_16apsk_mod model. Run with the EbN0 of the AWGN channel block set to 20 dB.

Change the EbN0 of the AWGN channel block to 10 dB. Run the model and observe the increase in noise.

Further Exploration

Adjust the modulation order in the M-APSK Modulator Baseband block. Before you run the model, you must also adjust the workspace variable M, defined in Model Properties> Callbacks> InitFcn to match the modulation order in the M-APSK Modulator Baseband block. The variable M sets:

• Set size in the Random Integer Generator block.

• Number of bits per symbol in the AWGN Channel block.

• Reference constellation in the Constellation Diagram. To see the user-defined reference constellation, open View> Constellation Properties and look at the Reference constellation tab.

If these parameters are not aligned with each other you will notice that the reference constellation and input signal do not produce the desired constellation.

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