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|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
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.
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
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|
|Appears in:||Thesis - Electrical Engineering|
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