OFDM for Wireless and Optical Communications

Abstract

This chapter is devoted to OFDM fundamentals and applications to wireless and optical communications. The chapter starts with the basic of OFDM including the generation of OFDM signal by inverse FFT. After that several basic manipulations on OFDM symbols, required to deal with multipath effects in wireless communications and dispersion effects in fiber-optics communications, including guard time and cyclic extension as well as the windowing operation, are described. Next, the bandwidth efficiency of OFDM is discussed. The next topic in the chapter is devoted to the OFDM system design, description of basic OFDM blocks, and OFDM-based parallel channel decomposition, including multipath fading radio and dispersion-dominated channels decomposition. Following the description of coherent optical OFDM (CO-OFDM) principles, the basic estimation and compensation steps, common to both wireless and optical communication systems, are described including DFT windowing, frequency synchronization, phase estimation, and channel estimation. Regarding the channel estimation, both pilot-aided and data-aided channel estimation techniques are described. Following the differential detection in OFDM description, the focus is on various applications of OFDM in wireless communications including digital audio broadcasting (DAB), digital video broadcasting (DVB), WiFi, LTE, WiMAX, and ultra-wideband communication (UWB). Next, optical OFDM applications are discussed starting with description of basic OFDM system types such as CO-OFDM and direct-detection optical OFDM (DDO-OFDM) systems. Regarding the high-speed spectrally efficient CO-OFDM systems, the polarization-division multiplexed OFDM systems and OFDM-based superchannel optical transmission systems are described. Before the concluding remarks, the application of OFDM in multimode fiber links is described.