Study, Implementation, and Simulation of OFDM and FBMC Systems in MATLAB

Overview

This project explores and implements two key multicarrier modulation schemes: Orthogonal Frequency Division Multiplexing (OFDM) and Filter Bank Multicarrier (FBMC) systems, specifically using Offset Quadrature Amplitude Modulation (OQAM). Both systems are simulated and analyzed using MATLAB to evaluate their performance, particularly in the context of 5G communication systems.

Table of Contents

Introduction to Modulation Schemes for 5G

1.1 Basics of OFDM 1.2 Further Multicarrier Modulation Schemes 1.2.1 Filter Bank Multi-Carrier (FBMC) 1.2.2 Generalized Frequency Division Multiplexing (GFDM) 1.3 Objectives

Detailed Analysis of OFDM

2.1 Advantages 2.2 Disadvantages 2.3 Implementation in MATLAB 2.4 Simulation Results

Detailed Analysis of FBMC

3.1 FBMC Physical Layer 3.2 Implementation using PHYDYAS Filter in MATLAB 3.2.1 Prototype Filter Design 3.2.2 OQAM 3.2.3 Frequency Spreading 3.2.4 Polyphase Network Implementation 3.3 Simulation Results 3.4 Comparison between OFDM and OQAM-FBMC

Conclusions

Introduction to Modulation Schemes for 5G

Multicarrier modulation is crucial for 5G communications. OFDM has been the dominant technology for broadband multicarrier systems. However, for applications like cognitive radios and uplink of multiuser systems, OFDM might not be ideal. FBMC is considered a promising alternative due to its efficient use of spectrum and reduced intercarrier interference (ICI).

Basics of OFDM

OFDM splits a high-rate data stream into several lower rate streams transmitted over multiple subcarriers, reducing delay spread and eliminating intersymbol interference (ISI) through guard intervals. Key parameters include the number of subcarriers, guard time, symbol duration, and subcarrier spacing.

Further Multicarrier Modulation Schemes

Filter Bank Multi-Carrier (FBMC) FBMC uses subcarrier filtering with OQAM, providing better spectral efficiency and reduced out-of-band emissions compared to OFDM. It does not require a cyclic prefix, saving bandwidth and power.

Generalized Frequency Division Multiplexing (GFDM)

GFDM is a flexible multicarrier method without strict orthogonality, suitable for cognitive radio applications. It manages out-of-band emissions well but has a more complex receiver design.

Objectives

The project aims to:

Understand OFDM and FBMC systems.

Implement and simulate these systems in MATLAB. Compare their performance, particularly in terms of Bit Error Rate (BER) and Power Spectral Density (PSD). Detailed Analysis of OFDM Advantages High spectral efficiency. Robustness against frequency-selective fading. Simplified channel equalization. Disadvantages High Peak-to-Average Power Ratio (PAPR). Sensitivity to frequency offset and phase noise. Implementation in MATLAB The OFDM system is implemented using MATLAB, focusing on the IFFT and FFT blocks for modulation and demodulation, respectively. Guard intervals are added to mitigate ISI.

Simulation Results

Simulations involve evaluating BER and PSD across different SNR levels. The results show expected performance aligning with theoretical predictions.

Detailed Analysis of FBMC

FBMC Physical Layer FBMC uses subcarrier filtering and OQAM to improve spectral efficiency and reduce out-of-band emissions.

Implementation using PHYDYAS Filter in MATLAB

Prototype Filter Design Designing the prototype filter involves setting the filter length and analyzing its frequency response.

OQAM

OQAM splits complex symbols into real and imaginary parts, transmitted with a time offset to maintain orthogonality.

Frequency Spreading

Frequency spreading improves spectral containment and reduces interference.

Polyphase Network Implementation

The polyphase network efficiently implements the filter bank, reducing computational complexity compared to the IFFT approach in OFDM.

Simulation Results

Simulations show FBMC's performance in terms of BER and PSD, highlighting its advantages in spectral efficiency and reduced interference.

Comparison between OFDM and OQAM-FBMC

FBMC demonstrates lower sidelobe levels and better spectral efficiency without the need for a cyclic prefix, making it more suitable for certain 5G applications.

File Descriptions and Usage Instructions

FBMC_Modulation_and_Demodulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of FBMC_Modulation_and_Demodulation.m into a MATLAB function file.
3. You can now use this function in your MATLAB scripts or command window.

Functionality:

• Implements both modulation and demodulation for FBMC signals.

fbmc_simulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of fbmc_simulation.m into a MATLAB script file.
3. Run the script in MATLAB.

Functionality:

• Simulates an FBMC system.

m_ary_qam_modulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of m_ary_qam_modulation.m into a MATLAB function file.
3. You can now use this function in your MATLAB scripts or command window.

Functionality:

• Performs M-ary QAM modulation.

OFDM_BER_Simulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of OFDM_BER_Simulation.m into a MATLAB script file.
3. Run the script in MATLAB.

Functionality:

• Simulates Bit Error Rate (BER) for an OFDM system.

OFDM_Modulator_and_Demodulator.m

Usage:

1. Open MATLAB.
2. Copy the contents of OFDM_Modulator_and_Demodulator.m into a MATLAB function file.
3. You can now use these functions in your MATLAB scripts or command window.

Functionality:

• Implements both modulation and demodulation for OFDM signals.

ofdm_qam_ber_simulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of ofdm_qam_ber_simulation.m into a MATLAB script file.
3. Run the script in MATLAB.

Functionality:

• Simulates Bit Error Rate (BER) for an OFDM-QAM system.

ofdm_simulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of ofdm_simulation.m into a MATLAB script file.
3. Run the script in MATLAB.

Functionality:

• Simulates an OFDM system.

OFDM_Spectrum_Analysis.m

Usage:

1. Open MATLAB.
2. Copy the contents of OFDM_Spectrum_Analysis.m into a MATLAB script file.
3. Run the script in MATLAB.

Functionality:

• Analyzes the spectrum of an OFDM signal.

OFDM_System_Simulation.m

Usage:

1. Open MATLAB.
2. Copy the contents of OFDM_System_Simulation.m into a MATLAB script file.
3. Run the script in MATLAB.

Functionality:

• Simulates an OFDM system with various parameters and analyzes the PAPR CCDF.

Conclusions

The study concludes that while OFDM is well-suited for many broadband applications, FBMC offers significant advantages in spectral efficiency and interference management, particularly for uplink multiuser and cognitive radio scenarios.

This README provides a high-level summary of the detailed study, implementation, and simulation of OFDM and FBMC systems in MATLAB. For in-depth analysis and MATLAB code, please refer to the full document.