MATLAB Code for Calculating BER of OFDM System with QPSK Modulation

In this article, we present MATLAB code for calculating the Bit Error Rate (BER) of an OFDM system with QPSK modulation. OFDM (Orthogonal Frequency Division Multiplexing) is a widely used digital communication technique that divides signals into multiple orthogonal subcarriers, each capable of carrying low-rate data streams. QPSK (Quadrature Phase Shift Keying) is a digital modulation scheme that maps digital signals onto complex constellations, effectively doubling the data transmission rate compared to BPSK. By combining these two technologies, we can achieve efficient and robust digital communication systems.

The MATLAB implementation includes key functions for OFDM transmission chain: signal modulation using qammod function with QPSK constellation, IFFT (Inverse Fast Fourier Transform) operation for OFDM symbol generation using ifft, and AWGN channel simulation using awgn function. The receiver chain implements corresponding FFT operation using fft function and QPSK demodulation using qamdemod. The BER calculation algorithm compares the transmitted and received bits using biterr function to compute the error rate.

We will detail the step-by-step code implementation process and demonstrate how to use it to calculate BER values for OFDM-QPSK systems under various signal-to-noise ratio (SNR) conditions. The code structure allows easy parameter adjustments for different OFDM configurations (number of subcarriers, cyclic prefix length) and QPSK parameters to optimize system performance. We will also discuss techniques for visualizing BER performance curves using semilogy function and methods to validate the simulation results against theoretical BER values for QPSK modulation.