Orthogonal frequency division multiplexing (OFDM) is a special case of multicarrier transmission and frequency division multiplexing, where a single data stream is transmitted over several lower rate subcarriers, placed orthogonal to each other. Today it is becoming the chosen modulation technique for wireless communications. It can provide large data rates with optimum bit error rate and enoug...

Index Terms—intensity modulation with direct detection (IM/DD), asymmetrically clipped orthogonal frequency division multiplexing (ACO-OFDM), optical communication.

The performance of Low-Density Parity-Check (LDPC)-coded Orthogonal Frequency Division Multiplexing (OFDM) is investigated over turbulence channels in underwater wireless optical communications (UWOC). relation between the bit error ratio (BER) and parameters such as scintillation coefficient, signal-to-noise (SNR), length LDPC code, order OFDM quantified by simulation. Results show that while ...

A novel least-squares (LS) scheme to estimate the channel frequency response (CFR) for orthogonal frequency division multiplexing (OFDM) over slow fading channels is presented. We take the advantage of slow fading to use repeated OFDM training blocks. This not only can facilitate the LS formulation but also improve the channel estimation performance as compared to the conventional one block LS ...

Two Per-Antenna-Coding (PAC) receiver schemes for Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) are described and compared in this paper. In MIMO, the data to transmit are multiplexed onto different antennas. With PAC (sometimes called horizontal coding), these different data streams are encoded separately. For the receiver, two schemes are proposed to ...

Increased data rates and reliability are the two key factors required to support emerging multimedia applications and new communications technologies. The two techniques used in high data rate transmission are orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) scheme. The OFDM is used to mitigate the problem of inter symbol interference (ISI) and provide...

In this letter, we propose a novel modulation concept which call index and composition (ICM). the proposed concept, use indices of active/deactive codeword elements compositions an integer to encode information. regard, first determine activated elements, then exploit energy levels these identify compositions. We depict practical scheme for using ICM with orthogonal frequency division multiplex...

Cooperative communication is a fourth generation novel scheme promising significant capacity and multiplexing gain in wireless communication. This paper derives the carrier to noise interference ratio (CNIR) and average bit error rate (BER) for orthogonal frequency division multiplexing (OFDM) based amplify and forward (AF) and decode and forward (DF) scheme over Nakagami fading channels. Numer...

Increased demand of multimedia system applications leads to high speed transmission speed that may be gratified by OFDM (orthogonal frequency division multiplexing). In wireless transmissions, OFDM is extremely smashing technology as it provides flexibility and high speed.One of the major drawbacks in the MIMO-OFDM is high peak-to-average power ratio (PAPR).Clipping & Filtering, Selected mappin...

High Peak to Average Power Ratio is one of the major drawbacks in Orthogonal Frequency Division Multiplexing (OFDM) which is used in Third Generation Partnership Project Long Term Evolution (3GPP LTE) in Downlink. In this paper, we review and analysis some pre-coding techniques in OFDM Keywords— OFDM, High Power Amplifier (HPA), PAPR