The Photoexcited carrier lifetime (τ) and peak to valley transmission difference (ΔTp-v) in direct and indirect band gap crystals has been investigated by the use of single beam open and closed aperture z-scan technique using frequency doubled Nd:YAG laser. The peak to valley transmission difference (ΔTp-v) is found to be of the order of 10-2 in case of direct band gap crystals and of the order...

Orthogonal frequency division multiplexing (OFDM) is, with substantial progress in digital signal processing, becoming an important part of the telecommunications arena. The most appealing feature of OFDM is the simplicity of the receiver design due to the efficiency with which OFDM can cope with the effects of frequency-selective multipath channels. Multicarrier systems such as OFDM are, howev...

Orthogonal Frequency Division Multiplexing (OFDM) is multicarrier modulation scheme for combating channel impairments such as severe multipath fading and impulsive noise. However, the principal disadvantage of OFDM is that it is highly susceptible to carrier frequency offset (CFO). Carrier frequency offset occurs due to frequency discrepancies between transmitter and receiver and Doppler shift ...

In this paper we concentrate on MPSK carrier frequency estmation based on random data modulation. We present a fast, open-loop frequency estimation and tracking techinque, which combines a feedforward estimator stucture and a recursive least square (RLS) predictor. It is suitable for the frequency estimation and large frequency acquisition and tracking required of burst mode satellite modems op...

In this paper, a type of multi-carrier direct sequence code division multiple access (MC-DS-CDMA) system which uses frequency spread coding is proposed and investigated for the down-link. An MC-DS-CDMA system is a combined system of CDMA and multi-carrier modulation. This system is often categorized as a “serial to parallel (S/P) type” system because serial to parallel converted data symbols ar...

Orthogonal frequency division multiplexing (OFDM) has been selected for broadband wireless communication system. OFDM can provide large data rates with sufficient robustness to radio channel impairments. One of the major drawbacks for OFDM system is Carrier frequency offset (CFO). Frequency offset has been recognized as a major disadvantage of OFDM. The OFDM systems are sensitive to the frequen...

Abstract::LTE is a new standard towards 4 generation in LTE OFDM is used as the basic multiple access technique. OFDM is very sensitive to Synchronization error in from carrier frequency offset because it can cause due to Doppler Shift and frequency mismatch and inter carrier interefernce which results in CFO. In this paper, we present algorithms for determining carrier frequency offset (CFO) f...

This contribution considers the Cramer-Rao bound (CRB) related to phase-independent carrier frequency estimation from a noisy PSK signal. Instead of estimating the frequency jointly with the carrier phase, we treat the phase as a nuisance parameter. Ideal symbol timing is assumed. Both cases of known data (training sequence) and random data are considered. We show that frequency estimation irre...

In this paper, we propose a joint carrier frequency synchronization and channel estimation algorithm for multipleinput and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. A major challenge to MIMO-OFDM systems is how to obtain the channel state information accurately and promptly for coherent detection of information symbols and channel synchronization. MIMOOFDM ...