A Master Thesis On Ofdm flat discount of 15% on all first-time orders. Free title page, formatting and referencing – we only charge for the pages that carry the content. Order Number OFDM Orthogonal Frequency Division MultiplexingOn Channel Estimation Techniques for MIMO-OFDM Systems Author: JiangLiJuan. Type: Masters thesis Year: Downloads: Quote: 2 Read: Download blogger.com thesis. Design of FIR-filter. Based on filtering a group of subcarriers, it combines the advantages of FBMC and OFDM while avoiding its drawbacks. In blogger.comted Reading Time: 8 mins This master thesis is focused on Orthogonal Division Frequency Multiplexing (OFDM) modulation applied in optical systems. OFDM is a well-known technique in communication systems, since it is used in
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Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up, master thesis on ofdm. Download Free PDF. An Efficient Technique for OFDM System Using Discrete Wavelet Transform Lecture Notes in Computer Science, Waleed Saad. Download Download PDF Full PDF Package Download Full PDF Package This Paper. A short summary of this paper. Download Download PDF. Download Full PDF Package. Translate PDF, master thesis on ofdm.
An Efficient Technique for Master thesis on ofdm System Using Discrete Wavelet Transform W. Saad, N. El-Fishawy, S. EL-Rabaie, and M. Shokair Dep. of Electronic and Communication Eng. com, nelfishawy hotmail. com, srabie1 yahoo. com Abstract. With the rapid expand of wireless digital communications, master thesis on ofdm for wireless systems that are reliable and have a high spectral efficiency have increased too. Orthogonal Frequency Division Multiplex- ing OFDM has been recognized for its good performance to achieve high data rates.
Fast Fourier Transforms FFT has been used to pro- duce the orthogonal sub-carriers. Due to the drawbacks of OFDM-FFT based system which are the high peak-to-average ratio PAR and the synchronization, many works have replaced the Master thesis on ofdm transform part by wavelet transform.
In this paper, an efficient technique for the OFDM system using wavelet transform is proposed. This system shows a supe- rior performance when compared with traditional OFDM-FFT systems through an Additive White Gaussian Noise AWGN channel.
The sys- tem performance is described in Bit Error Rate BER as a function of Signal to Noise Ratio SNR and the peak-to-average ratio PAR. Fur- thermore, the proposed system gives nearly a perfect reconstruction for the input signal in the presence of Gaussian noise. Keywords: Orthogonal Frequency Division Multiplexing, Fast Fourier Transform, Discrete Wavelet Transform, master thesis on ofdm.
To implement the OFDM transmission scheme, the message signal must first be digitally modulated. The carrier is then split into lower-frequency sub- carriers that are orthogonal to one another [1,2]. The message signal is first modulated using M-ary QAM.
With the advent of cheap powerful processors, the sub-carriers can be generated using FFT. The FFT moves a signal from the time domain to the frequency domain. While the inverse FFT IFFT performs the reciprocal operation. The cyclic prefix CP is a copy of the last part of the OFDM symbol, and is of equal or greater length than the maximum delay spread of the channel.
inter-symbol interference ISI [2]. The system model for FFT-based OFDM will not be discussed in detail in this paper as it is well known in the literature. Chang et al. Saad et al. OFDM has been chosen for several current and future communications ys- master thesis on ofdm all over the world such as asynchronous digital subscriber line ADSLdigital audio broadcast DABterrestrial digital videbroadcast DVB-T sys- tems, WiMAX systems, etc OFDM has several advantages compared to other type of modulation tech- niques such as bandwidth efficiency, overcome the effect of ISI, and combats the effect of frequency selective fading and burst error.
Nevertheless, the OFDM system has some weaknesses such as the high which means that the linear am- plifier has to have a large dynamic range to avoid distorting the peaks. The other limitation of OFDM in many applications is that it is very sensitive to frequency errors caused by frequency differences between the local oscillators master thesis on ofdm the trasmitter and the receiver [2].
Due to the OFDM drawbacks, master thesis on ofdm, wavelet transforms have been considered as alternative platforms for replacing IFFT and FFT. In OFDM wavelet based, the spectral containment of the channels is better since it does not use CP and, hence throughput increases [3,4,5,6,7,8,9,10,11].
In this paper, an OFDM system based on wavelet transform is proposed. The proposed system is simply implemented by a one level Haar wavelet. The system is comed with the traditional OFDM systems using MATLAB simulink programs. This paper is organized as follows; Section 2, gives an overview of the con- tinuous and discrete wavelet transforms and its inverse definitions.
Section 3, introduces a comprehensive discussion of the related previous works and the proposed OFDM based on wavelet transform architecture. The simulation re- sults and the comison tests between the proposed and traditional systems are made in Section 4. Finally, conclusions are made in Section 5. The Fourier Transform is probably the most popu- lar transform used to obtain the frequency spectrum of a signal.
But the Fourier Transform is only suitable for signals whose frequency content does not change with time. The Fourier Transform does not tell at which time these frequency components occur. To solve this problem, the Wavelet transform, which was de- veloped in the last two decades, provides a better time-frequency representation of the signal than any other existing transforms [12,6,4,13]. The Continuous Master thesis on ofdm Transform CWT is provided by eq.
ψ dt 1 s s Where x t is the signal master thesis on ofdm be analyzed, ψ t is the mother wavelet or the basis function, master thesis on ofdm, τ is the translation ameter, master thesis on ofdm, and s master thesis on ofdm the scaling parameter. Haar wavelet is one of the oldest and simplest wavelet. While Daubechies wavelets are the most popular wavelets. The DWT is just a sampled version of CWT. The signals are analyzed in CWT using a set of basis functions which relate to each other by simple scaling and translation.
While in the case of DWT, a time-scale representation of the digital signal is obtained using digital filtering techniques. The DWT is computed by successive lowpass and highpass filtering of the discrete time-domain signal as shown in figure 1.
Three-levels wavelet decomposition tree DWT Where n is an integer, master thesis on ofdm. The low pass filter is denoted by G0 while the high pass filter is denoted by H0. At each level, the high pass filter produces detail infor- mation, d[n], while the low pass filter associated with scaling function produces coarse approximations, a[n]. Three-levels wavelet reconstruction tree IDWT Figure 2 shows the reconstruction of the original signal from the wavelet coef- ficients or the inverse DWT IDWT.
Basically, master thesis on ofdm, the reconstruction is the reverse process of decomposition, master thesis on ofdm. In order to reconstruct the signal, a pair of reconstruc- tion filters G1 and H1 are designed such that output signal y[n] is identical to the input x[n].
This is known as the condition for perfect reconstruction PR [13]. Wavelet based OFDM provides bet- ter performance due to superior spectral containment properties. the IFFT and FFT blocks are simply replaced by IDWT and DWT wavelet fil- ter blocks respectively. In OFDM-DWT data modulation and demodulation are accomplished via IDWT and DWT operations respectively. Several works have been done in this field. In [6] the design of the transmitter and receiver for wavelet modulation and its performance in an AWGN channel have been outlined.
It has showed that the BER performance of wavelet modu- lation as function of SNR in the AWGN channel is more accurate.
In [8] different transmission scenarios concluded that DWT-OFDM performs much better than DFT-OFDM. But they observed an error floor in DWT- OFDM systems, master thesis on ofdm.
They suggested that it may be resulted from the Haar wavelet base. While in [4] the performance of Multicarrier Code Division multiple Access communication MC- CDMA for wireless Environment investigated in three transmission scenarios. Whereas in [7] the performance of five different most widely used Wavelet bases OFDM schemes over wireless channels has been studied.
BER versus SNR and an elapsed time for simulation of wavelet OFDM have been used as a measure of the system performance. In this paper, the DWT process is simply implemented by a one level 2- band reconstruction block as shown in figure 3.
The input signal x[n] is split by two filters G0 and H0 into a master thesis on ofdm pass component and a high pass component respectivelyboth of which are decimated down-sampled by 2. In order to reconstruct the signal, a pair of reconstruction filters G1 and H1 are designed according to the perfect reconstruction condition. Haar 2-tap wavelet has been chosen for this implementation. That is because the Haar wavelet is the simplest type of wavelets, fast, and memory efficient.
The filters coefficients corresponding to this wavelet type using MATLAB are shown in Table 1. The 2-band reconstruction block Table 1. At the transmitter, the random data bits are mapped into symbols to be modulated with Quadrature Amplitude Modulator QAM. Afterwards, the complex symbols are modulated via IDWT instead of IFFT then it is transmitted through the channel. An Efficient Technique for OFDM System Using Discrete Wavelet Transform At the receiver, the opposite operation is done.
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