Wireless Communication – Nine: OFDM

This is the ninth in a series of computer science lessons about wireless communication and digital signal processing. In these lessons you’ll learn about the nature of electromagnetic radiation, digital modulation and multiplexing techniques, and how to get the best out of mobile communication systems such as LTE, 5G and WiFi. In this particular lesson, you’ll learn about Orthogonal Frequency Division Multiplexing, OFDM. OFDM brings together and builds upon decades of research and development in the field of digital data modulation; it is the pinnacle of wireless communication technology. OFDM is so fast and spectrally efficient that it lies at the heart of many well-known communication applications including WiFi, WiMax, 3G-LTE, 4G , 5G, 6G, DAB radio, digital television, underwater communications, and even fibre optic cable networks. You will learn about the fundamental principles the underpin OFDM including frequency division multiplexing (FDM), the concept of orthogonal carriers, the discrete Fourier Transform (DFT), the Fast Fourier Transform algorithm (FFT) and the Inverse Fast Fourier Transform (IFFT). In addition, you will learn about the role of the cyclic prefix in an OFDM symbol and how it helps to maintain an acceptable peak to average power ratio. Chapters: 00:00 The history of OFDM 01:35 Multipath fading and Intersymbol Interference 06:12 Frequency Division Multiplexing 08:15 Orthogonal carriers 09:22 Discrete Fourier Transform 10:32 FFT and IFFT 11:45 Generating an OFDM symbol 15:05 Cyclic prefix 18:26 Summary