ogy, China Research Center of Intelligent Communication Engineering, School of Electronics and Communication Engineering, Guangzhou University, China Superscript(3)-N-P Semiconductor, San Jose, CA, USA 4 School of Electronics Engineering and Computer Science, Peking University, China OFDM History Orthogonal frequency division multiplexing (OFDM), as a special case of multicarrier transmission, is an elegant solution to the problem of high date rate transmission. OFDM was first developed to transmit data streams without inter-symbol interference (ISI) and intercarrier interference (ICI) in the 1960s [1]. A big breakthrough for efficiently imple- menting the OFDM system was made in the 1970s, when discrete Fourier transform (DFT) was applied to perform baseband modulation and demodulation in OFDM [2]. Another breakthrough in OFDM is the emergence of cyclic prefix (CP) in the 1980s [3], which main- tains orthogonality of the transmitted signals over multipath fading channels. In the 1990s, OFDM was exploited for wideband data communications. The first application in the com- mercial use of OFDM was digital audio broadcasting (DAB) in the 1980s and 1990s, where OFDM guarantees highly reliable data transmission over a high-velocity and complex environment. At the beginning of the 2000s, wireless local area network (WLAN) applied the OFDM technique to the physical layers [4]. In recent years, OFDM has been widely used for fourth generation (4G) and fifth generation (5G) wireless systems to increase the utilization of spectrum resources as well as to combat frequency-selective fading. The advantages of OFDM are summarized as follows: Resistance to frequency-selective fading Elimination of ISI and ICI Efficient use of the available spectrum Recovery of symbol lost by adequate channel coding and interleaving Enabling one-tap channel equalization However, every coin has two sides. The disadvantages of OFDM lie in the following: Large dynamic range of transmitted signal, or peak to average power ratio (PAPR) Sensitivity to 