Sameer A. Dawood

Discrete framelet transform based OFDM system using N-FRAT mapping over Rayleigh fading channel

This article proposes an N-finite Radon transform (N-FRAT) and a discrete framelet transform (FT) for the design of a new orthogonal frequency division multiplexing (OFDM) system. In the proposed system, the inverse FT (IFT) and FT were used instead of the inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) to realize multicarrier modulation and demodulation techniques, respectively. Simultaneously, it was suggested that the N-FRAT technique operate as a data mapper instead of the conventional phase shift keying (PSK) and quadrature amplitude mapping (QAM), which are usually used with the traditional OFDM system. The usage of the N-FRAT and FT in the proposed system led to an increase in the orthogonality between the subcarriers due to the application of IFFT in the N-FRAT, which was added to improve the orthogonality and time–frequency localization properties of the FT. Furthermore the proposed structure improved the bandwidth efficiency through the elimination of the cyclic prefix compared to the traditional system. The proposed system was simulated and compared with other OFDM systems, such as FFT based OFDM using N-FRAT mapping (N-FRAT-FFT-OFDM), FT based OFDM using QAM mapping (QAM-FT-OFDM), and FFT based OFDM using QAM mapping (QAM-FFT-OFDM). The simulation was performed over frequency selective fading channel using MATLAB technical programming language. The results of simulations showed that the new structure outperformed the other three systems by reducing the inter-symbol interference (ISI) and inter-carrier interference (ICI), which then improved the bit error rate (BER) performance.

Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System over Rayleigh Fading Channels

Discrete multiwavelet critical-sampling transform (DMWCST) has been proposed instead of fast Fourier transform (FFT) in the realization of the orthogonal frequency division multiplexing (OFDM) system. The proposed structure further reduces the level of interference and improves the bandwidth efficiency through the elimination of the cyclic prefix due to the good orthogonality and time-frequency localization properties of the multiwavelet transform. The proposed system was simulated using MATLAB to allow various parameters of the system to be varied and tested. The performance of DMWCST-based OFDM (DMWCST-OFDM) was compared with that of the discrete wavelet transform-based OFDM (DWT-OFDM) and the traditional FFT-based OFDM (FFT-OFDM) over flat fading and frequency-selective fading channels. Results obtained indicate that the performance of the proposed DMWCST-OFDM system achieves significant improvement compared to those of DWT-OFDM and FFT-OFDM systems. DMWCST improves the performance of the OFDM system by a factor of 1.5–2.5 dB and 13–15.5 dB compared with the DWT and FFT, respectively. Therefore the proposed system offers higher data rate in wireless mobile communications.

Performance comparison of STBC-FT based OFDM wireless communication system using M-QAM and M-PSK modulation techniques

This article investigates the comparative between the Bit Error Rate (BER) performance of Phase Shift Keying (PSK) and quadrature amplitude modulation (QAM) based on Space Time Block Coded Orthogonal Frequency-Division Multiplexing based on Discrete Framelet transform (STBC-FT-OFDM) system. This comparison is accomplished through simulation programs for different constellation points numbers for M-PSK and M-QAM (M = 4, 16, and 64) over an Additive White Gaussian Noise (AWGN), and Rayleigh multipath fading channels. The simulation results showed that the M-QAM modulation technique gave preferable BER performance compared with M-PSK modulation technique at all cases of constellation points and channels.

Performance Enhancement of Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System Using Hybrid Technique Under Different Channel Models

A hybrid technique, which is a combination of the Fast Fourier Transform (FFT) and Sliding Window (SW) technique, is proposed for the development of new structure for Discrete Multiwavelet Critical-Sampling Transform based Orthogonal Frequency Division Multiplexing (DMWCST-OFDM) system under multipath fading channels with the Doppler frequency effect. FFT is utilized to increase the orthogonality of subcarriers against the multipath frequency-selective fading channels. SW technique reduces the fluctuation of signal amplitude, thereby reducing the Doppler frequency effect. This hybrid technique offers a good tradeoff between performance and complexity, where this technique needs more computations. However, it performs better than the standard DMWCST-OFDM system. The performance of the proposed system, called SW-DMWCST-OFDM, was compared to that of the standard DMWCST-OFDM, SW-FFT-OFDM, and FFT-OFDM systems under three channels, namely, additive white Gaussian noise, flat fading, and frequency-selective fading. The simulation results show that the proposed model performs better than the three other models in all types of channels.

Performance enhancement of rake-receiver using continuous and discrete wavelet transforms analysis through NLOS propagation

In this paper, three levels of analysis and synthesis filter banks were used to create coefficients for a continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The main property of these wavelet transform schemes is their ability to construct the transmitted signal across a log-normal fading channel over additive white Gaussian noise (AWGN). Wireless rake-receiver structure was chosen as a major application to reduce the inter-symbol interference (ISI) and to minimize the noise. In this work, a new scheme of rake receiver is proposed to receive indoor, multi-path components (MPCs) for ultra-wideband (UWB) wireless communication systems. Rake receivers consist of a continuous wavelet rake (CW-rake) and a discrete wavelet rake (DW-rake), and they use huge bandwidth (7.5 GHz), as reported by the Federal Communications Commission (FCC). The indoor channel models chose for analysis in this research were the non line-of-sight (LOS) channel model (CM4 from 4 to 10 meters) to show the behavior ...

Performance analysis of a finite radon transform in OFDM system under different channel models

In this paper, a class of discrete Radon transforms namely Finite Radon Transform (FRAT) was proposed as a modulation technique in the realization of Orthogonal Frequency Division Multiplexing (OFDM). The proposed FRAT operates as a data mapper in the OFDM transceiver instead of the conventional phase shift mapping and quadrature amplitude mapping that are usually used with the standard OFDM based on Fast Fourier Transform (FFT), by the way that ensure increasing the orthogonality of the system. The Fourier domain approach was found here to be the more suitable way for obtaining the forward and inverse FRAT. This structure resulted in a more suitable realization of conventional FFT- OFDM. It was shown that this application increases the orthogonality significantly in this case due to the use of Inverse Fast Fourier Transform (IFFT) twice, namely, in the data mapping and in the sub-carrier modulation also due to the use of an efficient algorithm in determining the FRAT coefficients called the optimal order...

UWB selective rake receiver using multiple comparators

Recently, many literatures were presented to mitigate the noises or to suppress inter-symbol interference (ISI) and inter-frame interference (IFI) with systems operate in time hopping spread spectrum. The structure of the conventional rake-receiver is more complex that based on large number of multiple paths in wireless ultra wideband (UWB) communication systems. In this paper we proposed low complexity of rake-receiver that includes four fingers with additional finger used to support the outputs of other fingers by comparison process. This design is called multiple comparators rake-receiver. Low complexity receiver of maximum ratio combining (MRC) technique was simulated with perfect channel estimation. From simulation results, the optimized performance of the proposed scheme is presented by reducing the bit error rate (BER) with respect to conventional rake-receiver.

Performance analysis of multi-carrier code division multiple access system based on over-sampling multiwavelet transform over wireless channel

In this paper, an over-sampling inverse discrete multiwavelet transform (IDMWT) is suggested as a modulator strategy instead of inverse fast Fourier transform (IFFT) in the realization of the multicarrier code division multiple access (MC-CDMA) system. The suggested strategy was applied on the MC-CDMA with additive white Gaussian noise (AWGN) channel, flat fading channel and frequency selective fading channel. Simulation results showed that, the proposed method gives a better bit error rate (BER) efficiency than the traditional MC-CDMA model based on fast Fourier transform (FFT) and MC-CDMA based on discrete wavelet transform (DWT).

Comparison the performance of OFDM system based on multiwavelet transform with different modulation schemes

Orthogonal frequency division multiplexing (OFDM) is a very interesting approach for high data rate transmission in a multipath fading environment that leads to intersymbol interference (ISI). In this paper, two steps are used to improve the error rate performance of OFDM system. First, the discrete multiwavelet transform (DMWT) is proposed instead of fast Fourier transform (FFT) to obtain high orthogonality between subcarriers and hence reduce (ISI). Second, the performance of OFDM based on DMWT is examined for different modulation schemes such as M-PSK (M-ary phase shift keying) and M-QAM (M-ary quadrature amplitude modulation) to achieve high data rate. The simulation results demonstrated that, for high capacity data rate transmission, the M-QAM modulation is better than the M-PSK modulation.

Selective update euclidean direction search algorithm for adaptive filtering in indoor wireless rake-receiver

For high data rate propagation and indoor obstacles in wireless ultra-wideband (UWB) communication systems, the signal fading and noises are influencing the performance of the wireless systems. In this paper, the rake-receiver was presented with the spread signal by time-hopping spread spectrum (TH-SS) technique. The adaptive filter used in rake-receiver structure was shown with adjusting the receiver tap weights using Euclidean Direction Search (EDS) algorithm to support the weak signals by noise cancellation. To minimize the data convergence speed and to reduce the computational complexity by the previous algorithms, a well-known approach of selective-updates (SU) adaptive filter was employed with algorithms, such as sequential-selective, periodic-selective, and M-max-selective in the proposed system. The simulation results of bit error rate (BER) versus signal-to-noise ratio (SNR) are illustrated to show the performance of selective-update algorithm that has nearly comparable performance with the full update adaptive filters.