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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/1144

Title: SIMULATION OF A MOBILE RADIO COMMUNICATION
Authors: ROBEL, HADDIS
Advisors: Professor Wolde-ghiorgis Woldemariam
Copyright: 2003
Date Added: 20-May-2008
Publisher: Addis Ababa University
Abstract: The implementation of a simulation environment for mobile communication is very significant for Engineers and researchers of a mobile communication since it enables them to work in a environment that is almost similar with the practical one. Because multipurpose programmable digital signal processing have made it possible to implement digital communication like modulators and demodulators completely in software. The aim of this project work is to create and verify a channel model for a mobile radio channel. This model will later be used in the project to simulate digital transmission of data through a source(speech) coder, Channel coder and the modulator. When radio systems are simulated it is usually not practical to simulate the bandpass carrier signals. The high sampling frequency leads to unnecessarily long simulation time. Instead we use an equivalently complex low pass-model of the whole system. This study was designed in such a way that first the detail background theory of the subject matter is discussed in with alternative means of approaching the subject matter and why one technique is preferred amongst existing techniques is discussed after mathematical and logically presenting of the efficiency and effectiveness of the technique. The chosen technique will be discussed in detail and a software algorithm is formulated. Chapter 1 presents radio propagation path loss, link-budgets and log normal shadowing and describes a way to model and predict the fading, time delay spread and Dopler spread and describes how to measure and model the impact that signal bandwidth and motion have on the instantaneous received signal through the multipath channel of radio propagation in many operating environments. The various characteristics that produce and affect the channel will be simulated using the Spectrum method. Chapter 2 provides an introduction to speech coding. The goal of speech coding systems is to transmit speech with the highest possible quality using the least possible channel capacity. Linear predictive coding techniques are simulated in this thesis. Channel coding, error control coding and interleaving are presented in chapter 3 for error correcting capability that resist mobile channel impairments. Amongst these interleaving and reed-Solomon coding and decoding are discussed for software simulation. v Chapter 4 covers the most common and bandwidth efficient digital modulation techniques used in wireless communications and demonstrates the tradeoff that must be made in selecting a modulation technique. I tried to simulate the bandwidth efficient and error prone p/4 Differential Quadratic phase shift keying modulation scheme(QPSK) and compared for performance with the binary phase shift keying and the famous and efficient GSM modulation technique the Gausian minimum phase shift keying(GMSK). There are a number of factors that enter into the choice of a modulation scheme for use in a wireless application. Performance of a cellular system is dependent on the efficiency of the modulation scheme employed. Constant envelope modulation techniques, such as QPSK and GMSK, will be used to examine the features of each scheme and illustrate their uses in the cellular environment. The study of QPSK and GMSK is crucial to second and third generation cellular systems where achieving high capacity is the supreme factor. The goal of a modulation technique is not only to transport a message signal through a radio channel, but to achieve this with the best quality, power efficiency, and the least amount of bandwidth possible. In order to study the techniques for occupying less bandwidth and reducing power consumption per channel, a closer study of transmission techniques are explored in order to determine a favorable modulation technique for a particular wireless application. In portable radio systems where people communicate while walking or driving, these methods are used individually or in tandem to improve the quality (i.e speech coding reduce the bit error rate) of digital mobile radio communications in the presence of fading and noise.
Description: A thesis submitted to the School of Graduate Studies of Addis Ababa University in partial fulfillment of the requirements for the Degree of Master of Science in Electrical Engineering
URI: http://hdl.handle.net/123456789/1144
Appears in:Thesis - Electrical Engineering

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