Digital Communications MATLAB Simulink Project

Simulation and performance evaluation of the following modulation schemes in an Additive White Gaussian Noise (AWGN) envrionment:

Binary Phase-Shift Keying (BPSK)
Quadrature Phase-Shift Keying (QPSK)
Frequency Shift Keying (FSK)
Quadrature Amplitude Modulation (QAM)

Common steps to reproduce the simulation model:

Open MATLAB, run the simulink command from the command window.
In the Simulink window, click on New Model.
Click on Library Browser and drag and drop the required blocks:
- Modulator Baseband (Scheme Dependent)
- Demodulator Baseband (Scheme Dependent)
- Random Integer Generator (See Note 1)
- AWGN channel (set noise level to EbNo)
- Raised Cosine Transmit Filter
- Raised Cosine Receive Filter
- Constellation Diagram (x2)
- Error Rate Calculation
- Display
- To Workspace (set the name to ber)
Connect the blocks as shown in the screenshots using drag and drop.
Set the Simulation period to 100000 (With Raised Cosine Filters, it was set to 10000).
For QAM, there are more steps in the QAM section.
Save the model using Ctrl+S.

Common steps to reproduce the simulation model:

Run the bertool command from the MATLAB command window.
In the BER Tool window, set the E_b/N₀ range to -10:10
Choose the modulation scheme from the dropdown menu
Choose the Modulation Index (See Note 2) and click Plot
Open the Monte Carlo tab, set the E_b/N₀ range to -10:10
Set the Variable name to ber
Choose the model file using the Browse button and click Run

Note 1: Random Generator Set Size and Modulation Index should be set to the same value for each scheme. BPSK/FSk: 2, QPSK: 4, QAM: 16 or 64.

Note 2: Scatter plots are produced at a noise level of 10 dB.

Note 3: This project was created using MATLAB R2016a. Unless otherwise stated, all values are left to the default setting (e.g. Initial Seed in the AWGN Channel block is set to 67)

Binary Phase-Shift Keying Modulation (BPSK)

Explanation

BPSK is a modulation scheme which shifts the phase of the output signal depending on the input. The input is binary and the zeros and ones are represented by two different phase states in the carrier signal. The phase difference is 180 degrees.

BPSK without Raised Cosine Filter

Simulink Model Diagram:

Scatter Plot (Before Noise)

Scatter Plot (After Noise)

BER Performance Plot

BPSK with Raised Cosine Filter

Simulink Model Diagram:

Scatter Plot (Before Noise)

Scatter Plot (After Noise)

BER Performance Plot

Quadrature Phase-Shift Keying Modulation (QPSK)

Explanation

QPSK (A.K.A. Double Side Band Suppressed Carrier) is a variation of PSK in which two bits are modulated at once, selecting one of four possible carrier phase shifts (0°, 90°, 180°, or 270°). QPSK doubles the bandwidth efficiency leaving more space for other users.

QPSK without Raised Cosine Filter

Simulink Model Diagram:

Scatter Plot (Before Noise)

Scatter Plot (After Noise)

BER Performance Plot

QPSK with Raised Cosine Filter

Simulink Model Diagram:

Scatter Plot (Before Noise)

Scatter Plot (After Noise)

BER Performance Plot

Frequency Shift Keying (FSK)

Explanation

FSK is a digital modulation scheme in which the frequency of the carrier signal varies according to the digital signal changes. The output of a FSK-modulated wave is high in frequency for a binary High input and is low in frequency for a binary Low input.

FSK without Raised Cosine Filter

Simulink Model Diagram:

Scatter Plot (Before Noise)

Scatter Plot (After Noise)

BER Performance Plot

FSK with Raised Cosine Filter

Simulink Model Diagram:

Scatter Plot (Before Noise)

Scatter Plot (After Noise)

BER Performance Plot

Quadrature Amplitude Modulation (QAM)

Explanation

QAM is a scheme used to transmit two digital bit streams or two analog signals by modulating the amplitudes of two carrier waves so that they differ in phase by 90°. The two signals can be mathematically represented by a sine and a cosine wave.