Omar Daoud

An investigation of speech enhancement using wavelet filtering method

This paper investigates the utilization of wavelet filters via multistage convolution by Reverse Biorthogonal Wavelets (RBW) in high and low pass band frequency parts of speech signal. Speech signal is decomposed into two pass bands of frequency; high and low, and then the noise is removed in each band individually in different stages via wavelet filters. This approach provides better outcomes because it does not cut the speech information, which occurs when utilizing conventional thresholding. We tested the proposed method via several noise probability distribution functions. Subjective evaluation is engaged in conjunction with objective evaluation to accomplish optimal investigation method. The method is simple but has surprise high quality results. The method shows superiority over Donoho and Johnstone thresholding method and Birge-Massart thresholding strategy method.

Reducing the PAPR by utilisation of the LDPC code

Peak-to-average power ratio (PAPR) is a major drawback in most multi-carrier communication techniques such as orthogonal frequency division multiplex system (OFDM). OFDM consists of lots of independent modulated subcarriers, as a result the amplitude of such a signal can have very large values. These large peaks increase the amount of intermodulation distortion resulting in an increase in the error rate. The PAPR of an OFDM signal can be reduced in several ways: selective mapping, Golay sequences, cyclic coding, clipping and filtering, and multiple signal representation techniques. The authors have improved the performance of the OFDM system by using low-density parity-check (LDPC) codes as an alternative to turbo coding in mitigating the PAPR problem which has been used in the pervious works of the authors. The authors present the design for the proposed (LDPC) code technique that achieves good error correction performance and is used to lower the PAPR in a multiple-input multiple-output OFDM system. The simulation results show that 6-60- reduction in PAPR over current values in the literature can be achieved depending on the system type.

A new turbo coding approach to reduce the Peak-to-Average Power Ratio of a multi-antenna-OFDM system

A systematic procedure for a new approach to reducing the high Peak-to-Average Power Ratio (PAPR) of OFDM using turbo coding is described in this paper. Part of the produced symbol from the turbo coding process with low PAPR is sent instead of the original OFDM symbol, whilst the rest is sent through different antenna(s). This technique can support different types of modulation and coding techniques, and offers better results in both the CCDF and the BER than the conventional techniques currently proposed for this purpose, such as the clipping technique and the PTS technique, which presented by computer simulations.

MIMO-OFDM-based DVB-H systems: a hardware design for a PAPR reduction technique

Digital video broadcasting - handheld (DVB-H) is the technology driving mobile TV, which uses orthogonal frequency division multiplexing (OFDM) systems with multiple-input multiple-output technology (MIMO). These mobile communication systems have a promising future of supporting high data rate transmissions for both video and data. However, since the OFDM systems are sensitive to the peak-to-average power ratio (PAPR) problem, this work proposes a new technique (novel technique to reduce the PAPR based on turbo coding (NTRPT)), based on the turbo encoding technology, to reduce the PAPR effects for MIMO-OFDM-based DVB-H systems. This technique has been implemented and validated in hardware. It can support different types of modulation and coding techniques, and offers better results in reducing the PAPR than the conventional techniques currently proposed for this purpose, such as the clipping technique and the partial transmit sequence (PTS) technique, presented here using computer simulations

Peak-to-average power ratio reduction technique for MIMO/OFDM systems

Convolutional coding has been classically used in channel coding to provide Forward Error Correction (FEC) capability to the system by adding some carefully designed redundant information to the data being transmitted through the channel. However, in this work, we use convolutional codes for a different purpose: the reduction of the Peak-to-Average Power Ratio (PAPR) in an Orthogonal Frequency Division Multiplexing (OFDM) system by utilising these codes as spreading codes. This is an alternative to turbo coding and Low-Density Parity Check (LDPC) codes, which have been used for the same purpose in our previous works. The PAPR is a major drawback in most multicarrier communication techniques such as OFDM. OFDM consists of lots of independent modulated subcarriers; as a result, the amplitude of such a signal can have very large values. These large peaks increase the amount of intermodulation distortion, resulting in an increase in the error rate. The PAPR of an OFDM signal can be reduced in several ways: Selective Mapping (SLM), Golay sequences, cyclic coding, clipping and filtering and multiple signal representation techniques. Our results show that using LDPC coding in mitigating PAPR led to a 6%-60% reduction in this ratio, which is better than our proposed work based on either turbo coding or convolutional coding and the SLM and clipping techniques in the literature.

Efficient performance of COFDM-based DVB-T

European terrestrial digital video broadcasting (DVB-T) standard has been launched based on the well knows modulation technique; Orthogonal Frequency Division Multiplexing (OFDM), which when used in conjunction with channel coding is known as COFDM. This paper will show the efficiency of COFDM in different DVB-T environments based on a compliant DVB-T simulation. An efficiency performance study of COFDM systems-based DVB-T over three different channels has introduced. During this study, there were two different channel coding schemes used with two different coding rates, in addition to the use of two different modulation techniques. Also, using a strong modulation technique, such as 16QAM, will show better performance than the less power ones, such as the QPSK.

Wavelet transformation method to allocate the OFDM signals peaks

This work makes use of the entropy in order to propose a wavelet transformation algorithm to detect the odd peaks. Furthermore, this algorithm has been used to enhance the Orthogonal Frequency Division Multiplexing (OFDM) system performance based on combatting the peak-to-average power ratio (PAPR) problem. Three main stages are used to fulfill the process requirements; OFDM signal transformation based on the wavelet structure, thresholding process based on a predetermined criterion, and the filtration stage based on the moving filter. The proposed algorithm performance has been checked and validated not just numerically but also by a MATLAB conducted simulation. Furthermore, to check the simulation results, a comparison has been made to the literature; and shows promising results under the same bandwidth occupancy and systems limitations.

Enhancing the BER of MIMO-OFDM systems for Speaker verification

In this work a new algorithm has been proposed to improve the wireless systems that are compatible with the current new technologies. Therefore, Denoise Orthogonal Frequency Division Multiplexing (OFDM) symbols and Replace the high Peak-to-Average Power Ratio (PAPR); (DORP) has been modified. In DORP, wavelets techniques have been used to denoise the affected OFDM symbol by high PAPR values. After that and based on adaptive threshold method the local maxima and minima will be determined and replaced by the average of them and their surrounding neighbors. The algorithm mainly tackles and overcomes the effect of the high Peak-to-Average Power Ratio problem that is found in OFDM systems, MIMO-OFDM combination has been developed to meet the rapidly increment in the users demand such as the ubiquitous transmission, imposing new multimedia applications and wireless services. A system performance investigation process will be accomplished based on both of numerical method and MATLAB simulation. Moreover, a comparison has been made to check the validity of our proposition either with our previously published work or with the literature. Although, the achieved results show that the proposed work gives an improvement of the BER; an additional complexity has been added to transceivers structure. Moreover, and as a result to the comparison with the conventional systems, the bit error rate (BER) performance has been improved for the same bandwidth occupancy. As a validity process a comparison has been made with the current values found in the literature and we have achieved around 27% PAPR extra reduction. That is in addition to around 81% verification rate and noise immunity.

Improving the MIMO-OFDM systems performance-based GA

This paper proposes a new peak-to-average power ratio (PAPR) reduction method for a multiple-input multipleoutput (MIMO)-orthogonal frequency division multiplexing (OFDM) systems based on a genetic algorithm (GA). In this proposition we have combined a previously published work with the genetic algorithm to enhance both of the PAPR reduction ratios and computational load that are found in the literature. During this work, there was a comparison that has been stated among three techniques that were proposed to overcome the PAPR drawback; original Partial Transmit Sequence (PTS) technique, previously published work based on the linear coding and a modified version that combines the linear coding with GA. Finally, a range of simulation results are provided to demonstrate the superiority of the proposed scheme.

Evaluating the NGN performance based on duplicate transmission of voice packets

This work aims to enhance the Quality of Service (QoS) of the third-generation (3G) cellular networks. The quality of voice traffic over IP networks (VoIP) is greatly reduced due to the fact that packets in IP networks suffer from packet loss which is inevitable due to the best-effort nature of these networks. Many techniques have been proposed to decrease the effect of packet loss on the speech quality. In this paper we study the effect of packet loss on speech quality; we propose sending a duplicate copy of the speech stream over the network and we study the effect on the speech quality due to this duplication. This is especially useful in networks with extra available bandwidth. The performance of the system is measured according to the E-Model as defined in the ITU-Ts Recommendation G.107. The speech sources used during the experiments are artificial voices obtained from the ITU-T Recommendation P.50/Appendix I. The results of the proposed scheme suggest improvement in the system performance in terms of speech quality which can then be translated into greater percentage of users satisfied with the service and greater potential revenue. The proposed technique proves to be more effective when situations of higher percentages of packet loss and burst losses rise.