Getting Started

Modeling a Channel with Modulation

The Binary Symmetric Channel block, which simulates a channel with noise, is useful for building models of channel coding. For other types of applications, you might want to construct a more realistic model of a channel. For example, you can add modulation and demodulation, and replace the Binary Symmetric Channel block with an AWGN Channel block, which adds white Gaussian noise to the channel. This following figure shows an example that uses binary phase shift keying (BPSK).

BPSK Modulation Model

This section explains how to

• Build the model
• Set parameters in the model
• Run the model

The section also explains binary phase shift keying.

We encourage you to build the model for yourself. Alternatively, to open a completed version of the model, type bpskdoc at the MATLAB prompt.

Building the BPSK Model

You can build the BPSK model from the one shown in the figure Channel Noise Model. To build the model, follow these steps:

1. Type channeldoc at the MATLAB prompt to open the channel noise model, and then save the model as my_bpsk in the directory where you keep your work files.
2. Delete the Binary Symmetric Channel block from the model by right-clicking the block and selecting Clear.
3. Move the following blocks from the Simulink Library Browser into the model window, and insert them into the model as shown in the following figure:
• BPSK Modulator Baseband block, from PM in the Digital Baseband Modulation sublibrary of the Modulation library
• AWGN Channel block, from the Channels library
• BPSK Demodulator Baseband block, from PM in the Digital Baseband Modulation sublibrary of the Modulation library

The model should now appear as in the figure below.

Observing Channel Errors with the Scope

Binary Phase Shift Keying