Since an FFT-based speech encryption system retains a considerable residual intelligibility, such as talk spurts and the original intonation in the encrypted speech, this makes it easy for eavesdroppers to deduce the information contents from the encrypted speech. In this letter, we propose a new technique based on the combination of an orthogonal frequency division multiplexing (OFDM) scheme a...

Time-frequency-selective, equivalently time-variant multipath, fading channels in orthogonal frequency division multiplexing (OFDM) systems introduce intercarrier interference (ICI), resulting in severe performance degradation. To suppress the effect of ICI, several symbol detection methods have been proposed, all of which are based on the observation that most of the ICI’s power is distributed...

This paper will focus on improving the performance of orthogonal frequency division multiplexing (OFDM) in Rayleigh fading environments. The proposed technique will use a previously published method that has been shown to improve OFDM performance in independent fading, based on ordered sub-carrier selection. Then, a simple non-iterative method for finding the optimal bit-loading allocation was ...

The fast development of modern communication techniques, the demand for reliable high data rate transmission is increased signification, which stimulate much interest in modulation technique. The QAM is one of the adaptive modulation techniques that are commonly used for wireless communications. Different order modulations allow sending more bit per symbol and thus achieving higher throughput o...

Orthogonal Frequency Division Multiplexing (OFDM) has grown to a popular communication technique for high speed communication in the last decade. OFDM is an important member of the multicarrier modulation (MC) techniques and it has been adopted as a standard for various high data rate wireless communication systems due to its spectral bandwidth efficiency, robustness to frequency selective fadi...

The orthogonal frequency division multiplexing is used in wireless communication due to high data rate. OFDM are robustness against multi-path fading, frequency selective fading, and narrow band interference. Wavelet analysis has strong advantages over fourier transform and also allows time-frequency domain operation with flexibility. Wavelet is applied in various fields of wireless communicati...

Throughput is an important performance measure for data communications over a wireless channel. Orthogonal frequency division multiplexing (OFDM) with hybrid automatic repeat request (HARQ) achieves a good throughput performance over a frequency-selective fading channel. In OFDM with HARQ, however, during the first transmission uncoded information packet is transmitted. Consequently, the channe...

In this paper, a method for CFO/RFO estimation based on proportional coefficients extraction in OFDM system is proposed, which may be applied to any pilot symbol pattern. Keywords—OFDM (Orthogonal Frequency Division Multiplexing), CFO (Carrier Frequency Offset, Redundancy Frequency Offset), proportional coefficient extraction.

57  Abstract— OFDM (Orthogonal Frequency Division Multiplexing) is spectrally efficient modulation technique used for higher data rate transmission. Basically OFDM system is very effective technique in its way ,but main disadvantage is Peak to Average Power Ratio. This Ratio Must be reduce to perfom efficient communication. Different technique can be used to reduce it. Here in this paper propo...