Orthogonal Frequency Division Multiplexing in AWGN Channels

This chapter reviews generation of orthogonal frequency division multiplexing (OFDM) signals. In OFDM systems, Nc complex sinusoids, also called subcarriers, are used to modulate up to Nc data symbols for transmission in parallel over an ODFM symbol duration T. The frequencies of any two adjacent subcarriers are separated by the minimum separation required to maintain orthogonality between them. To ensure that the data symbols transmitted in parallel can be demodulated free of interference at the receiver, the complex sinusoids must be mutually orthogonal. The chapter then implements the demodulation process of OFDM signals, and simulates the bit error rate (BER) performance of OFDM signaling in additive white Gaussian noise (AWGN) environments. In a practical OFDM communications system, data are transmitted in frames. Each frame typically consists of many OFDM symbols. The chapter is designed to help teach and understand communication systems using a classroom-tested, active learning approach.