OFDM is an efficient modulation technique for wideband digital communication. A major drawback of OFDM modulation is the high Peak-to-Average Power Ratio (PAPR) of the transmitted signal which limits its transmission range of communication. As PAPR increases it reduces the average power which affect on total power consumption of Transmitter. Normally, OFDM is implemented using FFT. In recent ye...

Orthogonal Frequency Division Multiplexing (OFDM) converts a dispersive channel into parallel subchannels and thus facilitates equalization. But when the channel has nulls close to or on the FFT grid, OFDM faces serious symbol recovery problems. As an alternative to various error-control coding techniques that have been proposed to ameliorate the problem, we linearly precode (LP) symbols before...

This paper is concerned with a randomized OFDM (R-OFDM) scheme. The basic principle is to apply a scrambling operation to several OFDM frames. With a proper design strategy, the scrambling operation will not affect intra-cell orthogonality of OFDM (even considering multi-path effect). For signals from different cells, mutually random scramblings are used to reduce their correlation. This allevi...

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation scheme that provides efficient bandwidth utilization and robustness against time dispersive channels. This paper deals with the basic system model for OFDM based systems and with self-interference, or the corruption of desired signal by itself in OFDM systems. A simple transceiver based on OFDM modulation is present...

Orthogonal frequency division multiplexing (OFDM) has great advantages such as high spectrum efficiency and robustness against multipath fading. In order to enhance the advantages, an Hermitesymmetric subcarrier coding for OFDM, which is used for transmission systems like the asymmetric digital subscriber line (ADSL) and multiband OFDM in ultra-wideband (UWB) communications, is very attractive....

Abstract—Recently, the shortage of assignable radio frequency spectrum became a serious issue because of the coexistence of many licensed wireless communications systems. Therefore, cognitive radio technology has gained much attention around the world, which may be aware of its environment and makes occupancy of radio spectrum more efficient. This paper examines numerical results of active inte...

Optical OFDM was proposed for dispersion compensation in long-haul optical communications systems in 2006 in two forms, one using direct-detection and the other using coherent detection. Since then there has been extensive innovation towards developing intermediate forms of optical OFDM that are more suited to specific applications. This review paper presents our view on the developments in opt...

The goal of this contribution1 is twofold: i) an overview on the vast literature on recent advances related to OFDM modulators is given: Cyclic-Prefix OFDM, Zero-Padded OFDM, PseudoRandom-Postfix OFDM and IOTA-OFDM; these are identified to be potential candidates for fourth generation mobile communication networks in the framework of the IST-WINNER project. ii) The advantages/disadvantages of t...

Communication over doubly selective channels (both time and frequency selective) suffers from significant intercarrier interference (ICI). This problem is severe in underwater acoustic communications. In this paper, a novel partial fractional (PFrFT)-MIMO-OFDM system proposed implemented to further mitigate ICI. A new iterative band minimum mean square error (BMMSE) weight combining based on LD...

Alomouti’s space-time coding scheme for Multi-Input Multi-Output (MIMO) system has drawn much attention in 4G wireless technologies. Orthogonal frequency division multiplexing (OFDM) is a popular method for high data rate wireless transmission. OFDM may be combined with antenna arrays at the transmitter and receiver to increase the diversity gain and enhance the system capacity on time variant ...