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Item Experimental Verification of Image Perturbation Theory as Applied to the Accuracy of Area Measurement(Addis Ababa University, 1992-02) Hailu, Getacbew; Mullisa, Girma(PhD)photosensitive array, with inter-element spacing of & = 3cm is described. A mathematical formulation of perturbation applied to length & area measurement and contour detection is reviewed and presented. A description of the proposed experimental system is given. An area measurement error is defined and applied to the projected object images. It is found that static images (no perturbation) produces considerable error. It is then found that the applJlcation of a one dimensional sinusoidal image perturbation greatly reduces the area measurement error, while triangular image perturbation is optimum and theoretically results in zero error. Some practical applications of tbe system are suggested.Item Frequency Hop Spread Spectrum System Communication System(Addis Ababa University, 2003-01) Befekadu, Endale; Gopal, Devrajan (Professor)Among the various types of the spread spectrum systems the slow frequency hop spread spectrum system is discussed.In the transmitter the data input ,which is, text is converted to binary data by the ASCII code conversion table.This binary data is modulated using the the FSK modulator.Then pseudo-random frequencies are generated from pseudo-random code generators and a frequency synthesizer. Using these generated frequencies the modulator output signal is hopped or spread to different frequencies. After the spreading process, the final signal output is then transmitted through a non Gaussian plus Gaussian noise channel. At the receiver before the demodulation process the initial estimate of the receiver phase is made using the sequential detection method. Using the intial estimate of the phase the rest of the received phase is tracked using a second order tracking loop. After tracking the phase at the receiver end the next step is to dispread the frequency hopped signal. Then demodulation is carried out using the matched filter FSK detector .After detection the data output of the demodulator is converted back to text using the ASCII code table. Finally the receiver gets back the text data which was sent at the transmitterItem Simulation of A Mobile Radio Communication.(Addis Ababa University, 2003-02) Haddis, Robel; Woldemariam, Wolde-Ghiorgis(Professor)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.Item Fingerprint Recognition Using Hybrid Matching Algorithm(2003-08) Melese, Biniyam; Dagne, Assefa (PhD)Fingerprint matching is one of the most important problems in fingerprint recognition system. Generally, fingerprint matching algorithm can be classified into two: minutiae based and non‐minutiae based. In minutiae based matching, ridge endings and ridge bifurcations are used as discriminative features for matching, but in non‐minutiae based, features other than minutiae are used. Hybrid approaches by combining minutiae with other non‐minutiae based matching methods are used to improve fingerprint matching methods. In this paper, alignment‐based elastic matching algorithm, is used for minutiae based matching and new non‐minutiae method proposed which solve the shortcomings of the algorithms proposed by Jain et.al. The experiment was done on 320 fingerprints of Fingerprint Verification Competition 2002 set‐B databases and showed that the hybrid matching algorithm improved the Equal Error Rate from ~11.8 % to 7.55% than the minutiae based matching algorithm. Keyword: Image processing, Fingerprint recognition, local orientation, local frequency, minutiae, absolute average deviation from the mean, Gabor filter.Item Quantum Detection- Optimal Quantum Receiver Performance Analysis For Free Air Channel(Addis Ababa University, 2004-02) Oumer, Abdulrezak; Abdo, Mohammed (PhD)T h e f u n d ame n t a l p e r f o rma n c e l imi t s o f o p t i c a l c ommu n i c a t i o n s s y s t ems o p e r a t i n g o v e r t h e f r e e - s p a c e c h a n n e l wi l l b e e x ami n e d u s i n g q u a n t um d e t e c t i o n p r i n c i p l e . T h e p e r f o rma n c e o f t h e o p t imum q u a n t um r e c e i v e r f o r On /O F F k e y i n g a n d B i n a r y P h a s e - s h i f t k e y i n g Op t i c a l mo d u l a t i o n f o rma t i n t e rms o f q u a n t um me a s u r eme n t s t a t e s wh o s e p e r f o rma n c e i s o p t imi z e d v i a g e n e r a l i z e d r o t a t i o n i n H i l b e r t s p a c e i s f i r s t e x ami n e d a s a p u r e - s t a t e ( n o - n o i s e ) p r o b l em. T h e p e r f o rma n c e o f q u a n t um r e c e i v e r f o r M- a r r a y p u l s e - p o s i t i o n mo d u l a t i o n ( P PM) , wh i c h r e q u i r e s a p r o d u c t s t a t e r e p r e s e n t a t i o n , a n d (M- 1 ) d ime n s i o n a l r o t a t i o n a l A l g o r i t hm wi l l b e e v a l u a t e d wi t h t h e d e v e l o pme n t o f a n e f f i c i e n t r o t a t i o n a l a l g o r i t hm a n d a c omp u t e r p r o g r amme f o r c a r r y i n g o u t t h e r e q u i r e d n ume r i c a l o p t imi z a t i o n i s d e s c r i b e d a n d a p p l i e d . P e r f o rma n c e c omp a r i s o n s s h ows s u b s t a n t i a l imp r o v eme n t wh e n q u a n t um d e t e c t i o n p r i n c i p l e i s emp l o y e d . A s a f u r t h e r a p p l i c a t i o n o f t h e q u a n t um d e t e c t i o n p r i n c i p l e , t h e R e a l i z a t i o n o f q u a n t um d e t e c t i o n O p a r a t o r F o r M- a r r a y P h a s e s h i f t o p t i c a l mo d u l a t i o n f o rma t i s a l s o p r e s e n t e d .Item Adaptive Antenna Array Algorithms and Their Impact on Code Division Multiple Access Systems (CDMA).(Addis Ababa University, 2004-03) Hadgu, Dereje; Abdo, Mohammed (PhD)In mobile communications there is a need to increase the channel capacity. The increasing demand for mobile communication services without a corresponding increase in RF spectrum allocation (channel capacity) motivates the need for new techniques to improve spectrum utilization. The CDMA and adaptive antenna array are two approaches that shows real promise for increasing spectrum efficiency. This research focuses on the application of adaptive arrays to the Code Division Multiple Access (CDMA) cellular systems. The adaptive antenna has an intelligent control unit, so the antenna can follow the user, direct the radiation pattern towards the desired user, adapt to varying channel conditions and minimize the interference. Therefore there can be several users in the same channel in the same cell. The driving force of this intelligent control unit are special kinds of algorithms and we are going to investigate the performance of these different adaptive array algorithms in the CDMA systems. Four each blind adaptive array algorithms are developed, and their performance under different test situations (e. g. AWGN (Additive White Gaussian Noise) channel, and multipath environment) is studied. A MATLAB test bed is created to show their performance on these two test situations and an optimum one can be selected.Item Implementation of Energy-Efficient Routing Protocols for Mobile Ad hoc Networks (MANET(Addis Ababa University, 2004-08) Girma, Dereje; Abdo, Mohammed (PhD)The nodes in a mobile ad hoc network also form its routing infrastructure. Previous research shows that the idle power consumption in the nodes is significant, as the network interfaces on them is always on in order to maintain the routing fabric. As mobile nodes are dependent on battery power, there is a need for protocols that minimize energy consumption. In this thesis, the Dynamic Source Routing protocol used for on-demand routing in an ad hoc network is modified to reduce the power consumption in nodes by adaptively putting their interfaces to sleep. In an ad hoc network, it is impossible to predict accurately when it is all right for a node to put its network interface to sleep, using only its own information. In the approach presented, the time slot during which the interface is on is alternated with a time slot during which the interface is put to sleep. The duration of the on period depends only on indigenously available information about the number of packets the interface receives during this time slot. In the absence of any network activity in the on slots, the sleep period is linearly increased up to a maximum. The report explains all the factors that can affect the performance of the modified routing protocol and its influence on the energy consumption in the network. The penalty of increase in delay and packet loss is unavoidable and the levels of the factors are identified to minimize the penalty. The modified protocol is implemented in the Ns-2 network simulator. A linear equation is used to model the energy consumption for each node in the network. Simulations are conducted to test the modified protocol and the factors varied to study their impact. The results are compared with those obtained from the simulations using the unmodified DSR protocol. The results show average energy savings per-packet of up to 25% with an average of 2-3ms per-packet increase in the delay. The packet loss is comparable to the unmodified DSR protocol.Item Evaluation of Various Routing Protocols for Mobile Ad-Hoc Networks (Manets(Addis Ababa University, 2004-09) Awash, Etsegenet; Abdo, Mohammed (PhD)Mobile Ad-hoc NETwork (MANET), which is a concept of mobile communication without a fixed communication infrastructure, is one of the current emerging technologies gaining much attention from both researchers and users. Because there is no as such a fixed responsible device router, each computing node is to act as a router and should be willing to forward other’s packets. Routing in mobile computing is a difficult task as we have a very dynamic network topology. Another problem is, the nodes in ad-hoc network are usually laptops and personal digital assistants and are often very limited in resources such as CPU capacity, storage capacity, battery power and bandwidth. This means, any routing protocol running on a mobile node should try to minimize routing or control packets and also be reactive. A research work group established by IETF, has set a number of requirements to be met by an ad-hoc routing protocol. According to these requirements, a number of routing protocols have been proposed broadly into two main categories, proactive and reactive. In this thesis, a detailed discussion of routing protocols from both proactive and reactive group is presented followed by simulation work using a discrete event Network Simulator called NS-2. Because these groups of routing protocols fail to satisfy all the requirements of MANET under all conditions such as high mobility, big network size and large number of traffic sources, a new scheme of hybrid routing protocol is proposed. This new routing protocol, called ZRP, is to x take advantages from both proactive and reactive group of protocols. It alleviates scalability problem of other routing protocols by classifying the network into manageable sizes called zones. ZRP combines two different routing schemes in one protocol. IntrAzone routing uses a proactive protocol to maintain up-to-date routing information to all nodes within its routing zone. By contrast intErzone route discovery is based on a reactive route request and reply scheme. Simulation results of this thesis work shows that ZRP performs well under all conditions especially when we have large network size.Item Field Weakening Control of Pmsm(Addis Ababa University, 2005-01) Fita, Daniel; Mullisa, Girma (Professor)This master thesis deals with control of PM motor with field weakening capability for electric vehicle (EV) application .A PMSM motor model has been analyzed in a drive able to control the motor both in the constant-torque (constant flux) and in the constant-voltampere (flux weakening) regions. Today’s motor for traction in electric vehicle are most often induction motors. In recent years, PM-motors have become attractive due to their high efficiency. This is very important in battery applications. The first part of the project consists of a literature survey that aims at building knowledge on machine theory for field weakening. An analytical model for PMSM is developed there upon. An explanation of field weakening and the field orientation concepts implemented in the PMSM are presented. Finally, performance of field weakening control for PM machines with results is presented. Key words PMSM, field weakening, electric vehicleItem Incrementally Autonomous Light Weight Agent Architectures for Optimization Task(Addis Ababa University, 2005-03) Asnake, Nardos; Raimond, Kumudha (PhD)An agent oriented software engineering paradigm has been applied in solving engineering problems. In this work, agent architecture is developed that is suitable to solve a given problem. The system is developed progressively beginning from simple expert system to a system where agents learn to solve a given task based on some performance measure and agent architecture. Self-organization, emergence of global behavior and learning at population are considered while designing the agent architecture. Different ways of interaction and cooperation between agents are used to realize the collaboration among them. The transfer of problem solving task from human being to agents is clearly elaborated in the test scenario chosen for the worItem Comparative Study of Burst Error Correcting Capability of Cyclic and Convolutional Codes on Different Channels(Addis Ababa University, 2005-06) Desalegn, Genetu; Ayele, Hailu (PhD)Environmental interference and physical defects in the communication medium can cause Errors during data transmission. Coding is a method of detecting and correcting these errors to Ensure that information is transferred intact from its source to its destination. The error detecting and correcting capability of a particular coding scheme is correlated with Its code rate and complexity. A high code rate means information content is high and coding Overhead is low. However, the fewer bits used for coding redundancy, the lesser error Protection is provided. A tradeoff must be made between bandwidth availability and the Amount of redundancy added for error protection. There are many types of error correcting codes. Each code is distinguished by the method used To add redundancy and how much of this redundancy is added to the information going out of The transmitter. The type of errors that tend to occur on the communication channel determines the choice of The coding scheme for error protection. A channel with burst errors will tend to have cluster of Bit errors that occur during one transmission and thus different from channels with random Errors. The prime objective of this work is to compare burst error correcting capability of Cyclic and convolutional code on different channels. Viii To achieve the objective, (15,9) cyclic and (3,2,8) convolutional codes with burst length, l=3 , (21,9) cyclic and (3,2,13) convolutional codes with burst length, l=6 and (21,3) cyclic and (3,2,18) convolutional codes with burst length, l=9 are selected .probability of error , p(e) is Important parameter used to measure and compare the performance of the three selected codesItem ASSESMENT OF NEXT GENERATION NETWORK, SERVICES AND MIGRATION STRATEGIES The Case of Ethiopian Telecommunication Corporation(Addis Ababa University, 2005-08) Abrha, Bewket; Ayele, Hailu (PhD)The development of telecommunication systems during the past two decades has been from the circuit switched towards the packet switched paradigm. Initially a distinction was made between telecommunications and computer networks which is hardly applicable in today's reality. Incumbent network operators are running legacy circuitswitched telephony networks which inhibit them from enjoying the benefits of packet switching. Many operators have now started the paradigm shift in the telephony network by moving to packet based technologies. This new approach is often called Next Generation Networks (NGN). According to ITU Next Generation Network (NGN) is a packet-based network able to provide telecommunication services and able to make use of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies. It offers unrestricted access by users to different service providers. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users NGN enables the network operators to run all services on one network, i.e. voice, data and video. In this thesis the transformation of the legacy network to NGN in general and the Ethiopian Telecom migration in particular will be examined. This work reviews the evolution of voice telecommunications and attempts to analyze the network and service point of view as the industry migrates from circuit switched networks to packet switched networks. For the network part, the work tries to asses the legacy PSTN network elements with the NGN softswitched network. In the service part, a service modeling tool from Alcatel have been used to analyze and model next generation network services for the case of Ethiopian Telecommunication CorporationItem Source-Channel Prediction for Error Resilient Video Coding(Addis Ababa University, 2005-09) Negash, Kibrom; Ayele, Hailu (PhD)Over recent decades the role of image in the communication of information has grown steadly. Advances in technologies underlying the capture, transfer, storage, and display of images as a means of communicating information has become technologically and economically feasible. More importantly, images are in many situations an extremely efficient means to communicate information. The approach in this thesis work is to modify conventional motion compensation prediction so as to improve or optimize the error resilience performance of the over all system; motion compensated prediction in conventional video coders is based on the encoder reconstruction of the previous frame where motion is estimated so as to minimize the encoder prediction error. Such design paradigm optimizes the prediction at the encoder and ignores the effect of packet loss. The thesis work is based on the literature surveys, the simulation results are based on the H.263 software and the necessary computation is done on MATLAB. The modified (source-channel prediction) scheme achieves better error resilience performance and better over all R-D trade off than its conventional counter part.Item Speech to Text Conversion Using Amharic Characters(Addis Ababa University, 2005-12) Tsegaye, Nebiyou; Adugna, Enyew(PhD)Spoken language is the primary method of human to human communication. This communication by spoken language is now extended by use of technologies such as telephony, radio, etc. These technological advancements reflect that spoken communication is the preferred method in human psychology. Spoken language is also a preferred method of human-machine interaction. A spoken language system needs to have both speech recognition and speech synthesis capabilities. But this thesis is about building only the speech recognition (Speech to Text) system, specifically for Amharic language. Amharic language has more than 200 characters but the standard keyboard is made for English alphabet. This limited number of keys has imposed the need of 2 – 4 key strokes to write a single Amharic letter. The practical project of this thesis is to develop functional software with speech to text capabilities for Amharic language. But this software by no means covers all Ethiopic characters. The algorithms and models developed will be experimented on small part of the Ethiopic characters with minimal error rate as possible. There are different approaches to speech recognition. But the statistical approach to speech recognition seems to be industries current favorite, as it delivers better performance. It is also easier to implement. So the statistical approach is used in the development of the software. This approach requires acoustic models and language models to be built. Acoustic model refer to representation of knowledge about acoustics, phonetics, etc whereas Language viii model refers to system knowledge of what constitutes a possible word, what words likely to co-occur and in what sequence. This thesis is an attempt to build STT conversion for Amharic language using the statistical approach. So the inventory of speech files is made by recording and from these data appropriate models are built. The purpose is to test the performance based on the models built and prove that statistical models are suited to modeling speech signals.Item Development of Computer Program and Preparation of Design Aids for Commonly Used Sections of Rc Shear Wall Systems(Addis Ababa University, 2005-12) Mebrahtu, Kibrealem; Zekaria, Adil(PhD)In this paper capacity of commonly used reinforced concrete shear wall systems (rectangular, I-shaped, channel shaped, T and L-shaped) is graphically presented in order to provide design aids for the designers. When the section subjected to uni-axial and biaxial bending with axial compression the strength can be computed by assuming different position of neutral axis depth. For each position of neutral axis, the strain distributions across the section of the walls are determined. The stress in each reinforcement layers also determined from the known strain distribution. The strength of L-shaped or channel cross section subjected to axial compression and bi-axial bending can be computed based on the boundary condition for the concrete compression zone. To determine the boundary condition first the inclination of plane of bending (neutral axis inclination) with respect to x-axis is computed. Then axial and bending strength of concrete section can be determined by assuming different neutral axis depth perpendicular to the bending plane. Computer programs were developed for the analysis and design of rectangular, channel, I-shaped, L-shape, T-shaped reinforced concrete shear walls subjected to uni-axial bending with axial compression. Uni-axial design charts are also plotted for those shear wall sections (see in Appendix A). Moreover, for channel and L-shaped cross section shear wall systems, bi-axial interaction charts can be produced using the developed computer program for bi-axial bending. In addition, the program computes the required flexural vertical reinforcement for the given flexures (P, Mdx, Mdy).Item Grid Computing – Testbed and Application(Addis Ababa University, 2006-03) Asalefew, Abyot; Mengistu, DawitGrid computing, which is a type of parallel and distributed system that enables the sharing, selection, and aggregation of geographically distributed "autonomous" resources, is one of the currently emerging computing technologies gaining much attention from both researchers and end-users. This thesis is concerned with the study of concepts and components that are used in the deployment of computational Grid, including the testing of its middleware software Globus Toolkit. The study of Grid concepts and components performed by this thesis work includes the construction of sample Grid testbed, followed by testing its performance by using a sample computationally intensive LM Hash cracking application with customizations for Grid environment. As the technology becomes more pervasive and our technological world becomes more complex, without proper and timely acquaintance and understanding of the technology, stakeholders of AAU will find themselves at an increasing disadvantage. The work of introducing Grid computing, by deploying sample Grid testbed, to the users, students and researchers of AAU is one of the timely and economically appropriate works in this regard; and hence the other objective of this thesis work. This thesis also contains a detailed deployment and planning study of Grid construction in the AAU environment. This is further supported by a well-documented step-by-step installation and configuration procedure that is followed in the construction of the sampleGrid testbed.Item Intrusion Detection System for Mobile Ad-Hoc Networks (Manets)(Addis Ababa University, 2006-04) Desalegn, Konjit; Biru, Getachew(PhD)The term wireless networking refers to technology that enables two or more computing devices to communicate using standard wireless networking protocols. Strictly speaking, any communication technology that uses such a scheme could be called wireless networking. Based on the coverage area, wireless networking technology can be classified as wide area network (ex. Mobile cellular standards such as GSM, IS95) and local area networking (ex. WLAN such as the IEEE 802.11x). Furthemore wireless networks can be classified as infrastructure based, that is a wireless network with a central control device or access point (IEEE WLAN and GSM) , the second type of wireless networks is the so called infrastructure-less or Mobile Ad hoc networking (MANETs). This thesis deals with the analysis and implementation of two types of intrusion detection techniques for mobile Ad-hoc networks. Since MANETs have no established infrastructure: they are also described as self-organized peer-to-peer wireless network composed of mobile nodes. MANETs represent a dynamic network with no centralized control (i.e., a node can enter or leave a MANET group without collapsing the network). This property allows MANETs to change the network topology of a peer collection of mobile nodes with in the coverage range of each other, dynamically. However, this nature of ad-hoc wireless networks also makes them very vulnerable to an adversary's malicious attacks. To detect those malicious attacks the network needs an intrusion detection system. Various types of intrusion detection systems for wireless Ad hoc networks exist and are discussed in the next sections. In this thesis performance evaluation of the MANET routing protocol, Ad-hoc on demand distance vector (AODV) is done using the so called misuse IDS technique. Implementation aspect of the IDS for a particular type of attack, called resource consumption attack is done using the NS- 2 simulator, for the AODV routing protocol. A significant decrease in packet drop is obtained due to the application of the misuse intrusion detection algorithm. Other metrics such as energy consumption, delay are considered, and show improvement due to the application of the IDS. An in-depth discussion of the simulation results can be found in sectionItem Face Recognition Using Artificial Neural Network(Addis Ababa University, 2006-08) Endeshaw, Sentayehu; Raimond, Kumudha (PhD)In recent years, an explosion in research on pattern recognition systems using neural network methods has been observed. Face Recognition (FR) is a specialized pattern recognition task for several applications such as security: access to restricted areas, banking: identity verification and recognition of wanted people at airports. This thesis will explain what is involved in FR task and outline a complete Face Recognition System (FRS) based on Artificial Neural Network (ANN). In this work, two FRS are developed. The first model uses Principal Component Analysis (PCA) for feature extraction from the face images and ANN for the classification purpose. In the second model, combination of Gabor Filter (GF) and PCA are used for feature extraction and ANN for the classification. In the first approach, the face images are projected into subspace called eigenspace, consisting of the eigenvectors from the covariance matrix of the face images. The projection of an image into eigenspace will transform the image into a representation of a lower dimension which aims to hold the most important features of the face. These feature vectors are classified into training, validation and testing set. The training and validation set are used during the training of ANN. The testing set is used to evaluate the recognition performance of the model. In the second approach, Gabor feature vectors are derived from a set of downsampled Gabor wavelet representations of face images, then the dimensionality of the vectors is reduced by means of Principal Component Analysis (PCA), and finally ANN is used for classification. The Gabor filtered face images exhibit strong characteristics of spatial locality, scale, and orientation selectivity. These images can, thus, produce salient local features that are most suitable for FR. Experimentation is carried out on FRS by using Olivetti Research Laboratory (ORL) datasets, the images of which vary in illumination, expression, pose and scale. The result shows the feasibility of the methodology followed in this thesis work. Model 1 achieves a recognition rate of 76.6% whereas model 2 achieves 88.3% of correct classification and performed very efficiently when subjected to new unseen images with a false rejection rate of 0% during testing. The high recognition rate of model 2 shows the efficiency of GF in feature extraction. Key words—Face recognition, biometrics, artificial neural network, Gabor filter and principal component analysis.Item A survey on VLSI routing-algorithms and implementation(Addis Ababa University, 2006-09) W /Gebriel, Fasil; Amanuel, Gebre (PhD)VLSI (Very Large Scale Integration) physical design automation has been an area of great interest for the researchers in integrated circuit design. In earlier times physical design was done manually. The manual generation of layout designs has proved to be backbreaking, time consuming and error prone. In this thesis a rigorous study of VLSI switchbox routing algorithms and their implementation is done to evaluate the performance of these algorithms and to propose an algorithm which provides a better solution for some of the benchmark problems. A java implementation provides a graphical display of the result of execution of an algorithm under investigation and it also provides the number of tracks and vias a given problem requires to complete the routing.Item Design and Simulation of Multiband Microstrip Patch Antenna for Mobile Communications(Addis Ababa University, 2006-09) Mammo, Daniel; Abdo, Mohammed (PhD)In this thesis work a single band microstrip patch antenna having a narrow operating bandwidth around the GSM900 band is designed. Theoretical analysis and design was performed by the Finite Difference Time Domain (FDTD) method based on the electromagnetic field solver Empire software. To achieve the multiband antenna that can operate well in the: GSM (Global systems for mobile communication, 890-960 MHz), DCS (Digital cellular systems, 1710-1880 MHz), PCS (Personal Communication services, 1850-1990MHz), and UMTS (Universal Mobile Telecommunications Systems, 1920-2170MHz) bands. One needs to fine-tune the microstrip element to get dual band (GSM900 and GSM1800 bands) operation and to get a third or more operating band, one need to apply a shorted parasitic patch that is electromagnetically coupled to the main radiator. The multiband antenna posses 14-dB around the GSM 900 band of operation and greater than 8-dB return loss with bandwidths enough to cover the intended higher operating bands. As the proposed antenna can achieve such wide operating bandwidth with relatively low profile, it is very suitable for multi-band mobile communication handsets.