Communications Toolbox

Setting Up Parameters

The first part of the example defines variables that the rest of the example uses. The symbol alphabet has M different symbols, namely, the integers between 0 and M-1. The message is a column vector having len entries, each of which is chosen from the symbol alphabet.

The variables Fd and Fs refer to the relative sampling rates for the modulation scheme. They would be more meaningful if the example were sampling a real signal that had a natural notion of time. However, because this example uses a random signal that does not have a built-in notion of time, the main purpose of Fd and Fs is to indicate that the modulated signal has three entries for every one entry of the original signal.

• % Set up parameters.
  M = 8; % Number of symbols in alphabet
  len = 10000; % Number of symbols in the original message
  Fd = 1; % Assume the original message is sampled
  % at a rate of 1 sample per second.
  Fs = 3; % The modulated signal will be sampled
  % at a rate of 3 samples per second.
  

How the Example Works

Creating the Signal