In this paper, we consider different types of guard intervals for OFDM systems, i.e. cyclic prefix (CP), zero padding (ZP) and known symbol padding (KSP). We compare the different OFDM systems with respect to their SNR performance. We show that CP-OFDM and ZP-OFDM have exactly the same performance, whereas KSP-OFDM has a slightly worse performance. Further, we consider data aided channel estima...

In this paper an attempt is made to study the theoretical fundamentals for Coherent optical orthogonal frequency division multiplexing (CO-OFDM) for high speed, long haul optical transmission and investigated the nonlinear effect of a 16-QAM CO-OFDM and WDM CO-OFDM at 10Gbps data rate. We then demonstrated the transmission performance through simulation for single channel COOFDM and multi-chann...

Orthogonal frequency-division multiplexing (OFDM) modulation is a promising technique for achieving the high bit rates required for a wireless multimedia service. Without channel estimation and tracking, OFDM systems have to use differential phase-shift keying (DPSK), which has a 3-dB signalto-noise ratio (SNR) loss compared with coherent phase-shift keying (PSK). To improve the performance of ...

In this modern wireless technology Multicarrier communication is one of the more suitable and reliable communication technique. Orthogonal Frequency Division Multiplexing (OFDM) is used as modulation technique in multicarrier communication. The present paper gives an overview of OFDM and the various Channel Estimation techniques used in OFDM. The results implemented in MATLAB gives the performa...

In Orthogonal Frequency Division Multiplexing (OFDM) systems, the cyclic-delay diversity (CDD)Scheme is a low-complexity means of increasing transmit diversity. Because it requires only one inverse discrete Fourier transform (IDFT) operation at the transmitter. The mean square error (MSE) of both the least square (LS) channel estimate and the minimum mean square error (MMSE) channel estimate ar...

Orthogonal frequency division multiplexing (OFDM) combined with time division multiplexing (TDM), called OFDM/TDM, can overcome the high peak-to-average-power ratio (PAPR) problem of the conventional OFDM. Its bit error rate (BER) performance in a frequency-selective fading channel is improved by adoption of frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion...

Reliable channel estimation is indispensable for orthogonal frequency-division multiplexing (OFDM) systems employing coherent detection and adaptive loading in order to achieve high data rate communications. Several options exist in practical OFDM systems—including training symbols, cyclic prefix, virtual carriers, pilot tones, and receiver diversity—to facilitate channel estimation. In this pa...

Channel estimation is one of the most significant technologies in orthogonal-frequency-divisionmultiplexing(OFDM) . Inter-carrier-interference (ICI) occurs in OFDM which must be removed. There are various methods to reduce ICI in OFDM . Channel estimation techniques are used to investigate to reduce ICI in OFDM .In this paper we will discuss Channel estimation methods and DFT based channel esti...

Power line channel is the time-frequency variant channel with impulsive noise. Therefore, power line communication makes performance degradation due to time-frequency variant and impulsive noise. To overcome performance degradation, we consider the unitary signal constellation scheme and investigate the performance improvement of unitary matrix frequency modulated orthogonal frequencydivision m...

The next generation wireless communications require wideband information transmission with high data rates. Orthogonal frequency division multiplexing (OFDM) is recognized as a promising technique which can efficently overcome the multipath effect and inter symbol interference (ISI) of wideband wireless channels [1]. A dynamic estimation of channel is necessary before the demodulation of OFDM s...