School of Electrical and Computer Engineering

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Simulation of Flight Following System
(Addis Ababa University, 1989-06) Mathewos, Essatu; Klous, Kissig (PhD)
The simulation of the flight following system i6 primarily chosen in the interest of Ethiopian Airlines need to implement the system to replace the currently used flight following system which is based on verbal communication between aircraft and ground control people. The first section of this paper discusses the components of data communication system, aspects and objective of data communication system. The second section laid the emphasis on the fundamental communication concepts parallel transmission, serial transmission and the different types of serial transmission. The theory behind the simulation is basically based on the different types of transmission modes. The third section build the foundation for the characteristics of data transmission, direction of information flow: simplex, half-duplex and full duplex and finally rate of transmiesion effect on data transmission. In section 4 the different coding technology and structures are presented. A unique feature of the paper is section 5 protocol. There are sections on identifying and defining a problem in data communication specially for good understanding between a sender and a receiver.
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.
Design of Electrical Networks Through Computer-Aidedoptimization Techniques
(Addis Ababa University, 1993-06) Zewde, Solomon; Mullisa, Girma(PhD)
The objective of the study reported in this thesis has been to develop a unified algorithm for the computer-aided design of a wide range of electrical network configurations. While the design has been based on well-known techniques established earlier by other researchers, the present work has made significant contributions in simplifying the uses of nodal equation formulation method, graph theoretic concepts and topological formulas, as well as applications of a modified least p-th Taylor method, component damping techniques, sensitivity analyses and related design concepts. The basic computer-aided design approachfor a selected network was realized byfirst generating a voltage gain transfer function from the network connectivity details. Information concerning the gradient vector necessary in the course of an optimization process was then derived through a direct method of sensitivity analysis, without performing the normally needed first orderpartial differentiations. Comparison of a transfer function against desired response was preceded by sampling of the latter at selected frequency points and the whole adjustment was eventually automated via the least p-th Taylor method of optimization. It has been established that this approach avoided the time consuming calculation of a Hessian matrix that is usually required for performing network optimization. Convergence properties of the least p-th Taylor method were improved through a use of Fletcher's modification of the classicalLevenberg-Marquardt method together with component damping techniques. The concept of dynamic memory allocation has also been exploited. The resulting computer-aided network design technique was therefore efficient in terms of both processing time and memory requirements and the entire package has been termed as a Pascal program for optimal network design or P-POND. The algorithm has beenfully tested in its usefor designing both passive and active network types by specifying initial network parameters and input-output relations.
(7,3) Maximum - Length Binary Cycle Code Applied to Single Channel Digital Communication System for Error Correction
(Addis Ababa University, 1996-06) snegash, Yohanne; Alemu, Ketema(phD)
This paper presents the design and hardware implementation of the (7,3) maximum-length binary cyclic code applied to a single channel communication system. In hardware implementation of the system a PC with a data acquisition board with time <- sharing for interfacing the analog signals. A 12-bit digital output of the PC is divided into blocks of 3-bits for processing by the channel encoder The implementation of the system is carried out using shift registers and logic gates. A sinusoidal input waveform is applied to the system input and a circuit designed with a combination of D-type flip-flops and logic gates is used to introduce the effects of a single-random-error and a double-adjacent-burst error to observe the performance of the system. The code resulted in good performance in correcting a single-random-error and a double-adjacent-burst-error.
Neural Network Implementation of Character Recognition
(Addis Ababa University, 1998-05) Bireda, Tezazu; Adugna, Eneyew(PhD)
Artificial neural networks, as they are usually called, currently gained much popularity in the design of "intelligent" machines and in programs which are used for automatic pattern recognition as pattern classifiers. In contrast to symbolic-oriented methods in artificial intelligence (Al), artificial neural networks are computing systems that use mathematical algorithms and "imitate" the way the brain, the biological neural network, functions. They are made up of a number of simple, highly connected non linear processing elements and process information by their dynamic state response to external inputs. They are characterized by the ability to learn and generalize, massive parallelism which gives rise to greater speed on computers with parallel processors or on a dedicated analogue VLSI circuit chip, tolerance to significant erroneous data or network fault, and some models exhibit self organization in the learning phase giving optimum network architecture. Their greatest asset compared to other recognition methods, however, is their ability to learn and generalize. In this paper a feed-forward Back Propagation Network (BPN) architecture, which is one of the several network architectures available, is implemented to recognize printed multifont alpha-numeric (English and Amharic or Geez) characters and its performance is investigated. The network model has three layers and is trained in a supervised training mode. In the research, two independent sets of pattern classes of characters were formed each pattern class having four training and two testing sample character patterns. The first set deals with randomly selected pattern classes and the second set deals with very similar pattern classes. And in both sets of training and testing schemes, the relative recognition performance of the network is evaluated. The network recognition rate or performance, only for the test patterns, in percentage for the first set is about 85% and for the second set is about 67%. The overall recognition rate accounting tests with both the training and test patterns is 93% for the first set and 87% for the second. When the test patterns from these two sets were corrupted with noise, the recognition performance of both sets degraded steadily. Test was also made with tilted test patterns on the first set and the performance was unaffected up to a tilt angle of 4.4 degrees from the vertical. A steady improvement in performance was observed as the dimension of the input pattern vectors, the number of training patterns in a pattern class, and network size were increased.
Design and Realization of an Audio Frequency Filter Unit for Shortwave Communication System Using TMS320CSO DSP Kit
(Addis Ababa University, 1998-12) Mengesha, Seble; Haferkorn, Habil P(PhD)
Causes that may affect the quality of shortwave data communication over radio are presented. Designing an audio-frequency filter unit, other than the filters exist in the transceiver, is considered as one solution to improve the quality of this shortwave data communication. Among the different data communication modes exist in the communication system, the CW (continuous wave), RTTY (Radio teletype) and AMTOR (amateur teleprinting over radio) types are selected to test the performance of the designed filter unit. The filter unit is of FIR digital filter type which the impulse response coefficients are obtained using the Kaiser Window design technique. The DSK (digital signal processor starter kit) assembler and debugger are used to develop the assembly code so as to realize and implement the filter on TMS320C50 digital signal processor. The magnitude response of the resulting filter unit is estimated by a spectrum analyzer. Finally, the designed filter unit is tested in an Amateur Radio Communication System.
Coding and Transmission of Non Uniform Alphabets
(Addis Ababa University, 1998-12) Kassahun, Yohannes; Ayele, Hailu (PhD)
Two algorithms are developed in such a way that the decoding and encoding times for Huffinan encoding scheme are minimized. Algorithm One is tested for compression and decompression of text files, while Algorithm Two is tested for compression and decompression of any form of file, real time text transmission, and compression and decompression of bitmap graphics files. Programs used in the implementation of the developed algorithms in the above mentioned applications are presented. Results of the implementations are also included.
Feasibility Study of Renewable Energy Resources for Electrification of Small Islands. A Case Study on Tana Lake Islands
(Addis Ababa University, 2002) Mekonnen, Abiyot; WoldeMariyam, WoledeGiorigs (PhD)
The energy problem of islands differs from those in mainland countries because islands need to manage their own energy supplies. The islands are good test beds for the utilization of renewable energy production and storage technologies. The present study relates the main renewable energy resources to the electrical production in the small islands in Lake Tana. The necessity to integrate some renewable energy resources is shown and various storage means are classified. Also, the needs for hydro pumping storage are proposed and investigated as a good solution for promoting to the increase of the penetration rate of renewable energies, particularly in island electrical grid interconnections. In Ethiopia there are two lakes which have Islands (Lake Tana and Lake Zeway). Among them, the island on Lake Tana (Deck Island) is the biggest Island in the country having a total population of about 7000 human residents within five villages. Due to the location of the Island is so far the task of their electrification via grid system very difficult. Kerosene is used for lighting; with diesel power generation isfor milling and pumping, leaving biomass for cooking and dry cells for radio which are being used in this Island. Nothing has been done so far in developing the renewable energy resources, such as small-scale hydro, solar, and wind energy in the Island. In this work, feasibility of renewable energy resources for electric supply system to this small Island is studied using HOMER (Hybrid Optimization Model for Electrical Renewables) software as optimization and sensitivity analysis tool. Meteorological data from National Meteorological Agency of Ethiopia and other sources, such as NASA, have been used for the estimation of solar and wind energy potentials. Electric load for the basic needs of the community, such as, for lighting, radio, television, electric baker, water pumps and flour mills, have been estimated. Primary schools and health posts are also considered as energy users for the community. As a result, based on the storage system, PV/Wind/pumped hydro hybrid system combinations is found as having a cost of energy about $0.151/kWh which is much lower than diesel generators and previously studied PV-battery hybrid systems which is estimated to cost about $0.325/KWh Key words: Wind, Solar, Hybrid, HOMER, Pumped hydro, Load Estimation 8 M.sc Thesis by Abiyot Mekonnen in Electrical power Engineering ECE DeptsAAit Table
Internet Self-Similarity, Modelling and Performance Evaluation
(Addis Ababa University, 2003-01) Abdulkadir, Taye; Devarajan, D (Professer)
Understanding the nature of traffic and its associated delay process in high traffic systems, such as the Internet, is essential for Engineering, Operations & Performance evaluation of these networks. It has been a common practice to assume packet arrivals as a Poisson Process in modelling high Traffic Networks. However, data communication traffic levels fluctuate over time, and delays through congestion can occur even on lightly utilized links. These fluctuations can occur over very short periods of time giving rise to the concept of a burst of traffic. This high variability or bursty nature can be explained through Self-Similarity and Long-Range Dependence. In this thesis work an attempt is made to verify the Self-Similarity or Long-Range Dependence nature of Internet Traffic and its associated Packet Round Trip Delay process. Also Fractional Auto-Regressive Integrated Moving Average (FARIMA) Model is found to fit the long memory as well as the short memory properties of the collected Internet Traffic Data. An artificial traffic trace synthesis program based on the FARIMA model is also developed. While the research convincingly establishes the presence of LRD over a wide range of time scales in the packet traffic and delay processes, its implication to Queueing performance is a center of argument, in one hand arguments acknowledging LRD in packet traffic affecting Queueing performance, and in the other hand arguments emphasizing LRD has no practical impact and need not be incorporated into performance models. In this research it is tried to do experimentation, which demonstrates the first argument, that LRD in traffic indeed affects Queueing Performance. TCP, the reliable transport protocol of TCP/IP, employs an ACK (acknowledgment)-based window control, that is, a TCP sender updates its congestion window size every time it randomly measures Round Trip Time (RTT) or Packet Round Trip Delay. With the most basic mechanism in the Internet to detect losses, the sender re-transmit a segment if it's ACK has not been received in the expected amount of time. Therefore, TCP throughput performance depends on the RTT. Investigation on the relation between RTT Self-Similarity and TCP throughput performance as measured by the amount of bandwidth wastage due to premature timeouts is also covered. vi Real time traffic must get a fairly regulated number of packets through to the destination in a timely manner. If these packets are late enough to have missed their “play” window, they are useless. Voice over Internet Protocol (VoIP) is one real-time application carried over the Internet. Packet delay variations in Internet tend to create voice degradations, unless proper Quality of Service (QoS) measures are implemented. In this thesis work investigation on Packet Delay and VoIP relations have been done and QoS measures suggested.
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 transmitter
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.
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.
Design and Realization of Adaptive Channel Equalizer for Shortwave Communication using TMS320C50 DSP Kit
(Addis Ababa University, 2003-12) Ayalew, Mesfin; Haferkorn, Habil P(PhD)
The high frequency (HF) band is a cost effective medium for a long distance transmission beyond the horizon, for limited bandwidth of up to 3 kHz. However, the HF channel is simultaneously a time and frequency dispersive environment. Time spread is two fold and results from multiple reflections between earth surface and ionosphere, where the latter is known to have various reflection layers. This multipath behavior results in various received modes at the receiver site corresponding to a time spread of a few milliseconds. Frequency spread is due to motion of electron density distributions in the ionospheric media, and can be as high as 10 Hz. In addition to time and frequency spread the relative movements of ionospheric layers impose a Doppler shift on transmitted signals. The received signal in fading often modeled by a Rayleigh distributed envelope and a uniformly distributed phase. Frequency selective fading channels produce intersymbol interference (ISI) in the received signal. In these channels an increase in the power does not improve performance, since additional power amplifies the ISI in step with the desired signal. The maximum likelihood sequence estimator (MLSE) is the optimal method of canceling the ISI; however, it is prohibitively complex. Suboptimal but efficient method of compensating for the ISI is to equalize the channel impairments by applying a filter at the receiver. In general radio channel characteristics are subject to variation in time, and this leads to the need for adaptive equalizers. In this development, a linear frequency selective slowly fading model is used for the channel. A linear adaptive channel equalizer is considered as a solution to improve the performance of digital communication over this short wave channel. The performance of the equalizer is studied under a software simulated environment using MATLAB programming for a linearly modulated, binary phase shift keyed (BPSK), signals. The TMS320C50 DSK (digital signal processor starter kit) assembler and debugger are used to develop the assembly code so as to realize and implement the filter on TMS320C50 digital signal processor. Finally, the designed equalizer is tested for its performance.
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 .
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.
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.
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.
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 vehicle
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 wor
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 codes

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