说明：  Introduction This section builds an example step-by-step to give you a first look at the Communications System Toolbox™ software. This section also shows how Communications System Toolbox functionalities build upon the computational and visualization tools in the underlying MATLAB® environment. Modulate a Random Signal This example shows how to process a binary data stream using a communication system that consists of a baseband modulator, channel, and demodulator. The system s bit error rate (BER) is computed and the transmitted and received signals are displayed in a constellation diagram. The following table summarizes the basic operations used, along with relevant Communications System Toolbox and MATLAB functions. The example uses baseband 16-QAM (quadrature amplitude modulation) as the modulation scheme and AWGN (additive white Gaussian noise) as the channel model.