الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Communication is one of the important aspects of life. With the advancement in age and its growing demands, there has been rapid growth in the field of communications. Signals, which were initially sent in the analog domain, are being sent more and more in the digital domain. These days, for better transmission, even single carrier waves are being replaced by multi-carriers. Multi-carrier systems like CDMA and OFDM are nowadays being implemented commonly. In the OFDM system, orthogonally placed subcarriers are used to carry the data from the transmitter end to the receiver end. Presence of guard band in this system deals with the problem of Inter Symbol Interference (ISI) and noise is minimized by larger number of subcarriers. But the large Peak to Average Power Ratio of these signal have some undesirable effects on the system.
Several techniques have been proposed in the literature to reduce the Peak to Average Power Ratio (PAPR). These techniques can mainly be categorized into signal scrambling techniques and signal distortion techniques. This thesis takes an overall look at these issues. Detailed discussion about two proposed PAPR reduction techniques will be presented. These two techniques are based on using two techniques. The first is the arithmetic coding and the second is the principal component analysis (PCA). The first proposed method is based on coding the input data using arithmetic coding. Arithmetic coding is a very useful when dealing with sources with small alphabets, such as binary sources, and alphabets with highly skewed probabilities, which is the case that gives high PAPR so we used it to decrease the PAPR. The proposed PCA method reduces PAPR by applying PCA transform to the modulated symbols before the IFFT and the reverse operation is performed at receiver. As we will see from the final results it’s evident that the two proposed schemes give acceptable amount of reduction and may be considered as promising schemes in an OFDM system.
Organization of the Thesis
This thesis consists of 5 chapters, which cover Orthogonal Frequency Division Multiplexing (OFDM) system definition and PAPR reduction techniques.
In Chapter 1, an overview of the wireless communication system combined with mobile generation are introduced. Then a description of the Orthogonal Frequency Division Multiplexing (OFDM) system and illustration of its numerous advantages are considered. Finally the main drawbacks in OFDM are discussed.
In Chapter 2, various recent PAPR reduction techniques are proposed for reducing the PAPR and the selection criteria for choosing these techniques have been discussed.
In Chapter 3, arithmetic coding is presented as a PAPR reduction technique. In this chapter the main steps of generating the code and the power amplifier model will be discussed. Also the simulation results which illustrate the effect of using arithmetic coding in the amount of PAPR reduction value will be introduced.
In Chapter 4, PCA is presented as a PAPR reduction technique. In this chapter an overview about PCA and the simulation results which illustrate the effect of using PCA in the amount of PAPR reduction value will be introduced.
In Chapter 5, conclusions of the obtained results are drawn and brief recommendations are given.