Near-Ultrasonic Wireless Orthogonal Frequency Division MULTIPLEXING MODEM DESIGN

This chapter discusses transmission of an image file over a near-ultrasonic (NUS) wireless channel. The image file is orthogonal frequency division multiplexing (OFDM) modulated and transmitted from the speaker of a phone over an NUS wireless channel. The microphone in a PC samples the received signal and demodulates it to restore the image data. The chapter investigates transmit and receive algorithms for NUS OFDM systems. It also analyzes the waveforms and spectra of NUS systems at major processing stages. To demodulate each OFDM symbol, one needs to separately perform fast Fourier transform (FFT) on the properly partitioned portions of rcbb. The vector rcbb is the sampled version of the frequency-offset compensated complex baseband signal. Proper partitioning of rcbb requires locating the starting sample of each OFDM symbol. The chapter is designed to help teach and understand communication systems using a classroom-tested, active learning approach.