UDC 621 A REVIEW ON ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING © Kamakshi Rautela, M. Tech Scholar, Graphic Era Hill University, Bhimtal Campus, India Mohit Pant, Assistant Professor, Graphic Era Hill University, Bhimtal Campus, India Abstract. <...> In today’s era of wireless communication system channel estimation is very important. <...> OFDM (Orthogonal frequency division multiplexing) plays a very important role in channel estimation. <...> In July1998, OFDM was selected as the basis for new 5-GHZ standard as decided by the group of IEEE standardization. <...> OFDM was first used in the packet house by IEEE standardization group. <...> The main aim to use OFDM is to divide the available spectrum into a number of orthogonal subcarriers in parallel, so OFDM is said to be one of the parallel transmission techniques. <...> This paper will review the principal of OFDM, the modern OFDM modes, PAPR problem. <...> Shortly after Chang presented his paper, Saltzberg performed an analysis of the performance [2], where he concluded that “the strategy of designing an efficient parallel system should concentrate more on reducing crosstalk between adjacent channels than on perfecting the individual channels themselves since the distortions due to crosstalk tend to dominate”. <...> A major contribution to OFDM was presented in 1971 by Weinstein and Ebert [3], who used the discrete Fourier transform (DFT) to perform baseband modulation and demodulation. <...> Basic block diagram of OFDM [10] 116 Engineering and Automation Problems, № 2 – 2017 A REVIEW ON ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING analogous to FDMA where each carrier signal has their own signal band and all bands are multiplexed together and transmitted along the single channel. <...> This multiplexing technique OFDM is employed for achieving the high data rate. <...> Multicarrier modulation is nothing more than a parallel data transmission system. <...> Transmission of binary data over the single side band voice channels was implemented by Doelz et al. in 1957 [5]. <...> As each subcarrier of OFDM has different frequency. <...> The frequencies of a subcarrier are distributed in such a manner that the signals become orthogonal to each other. <...> The basic block diagram of OFDM is given below: It is made up of: P <...>