Communication Engineering

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Analysis and Design of A Compact Microstrip Patch Antenna With Enhanced Bandwidth and Gain for Wireless Local Area Network (Wlan) Communications
(Addis Ababa University, 2010-07) Debo, Feyisa; Abdo, Mohammed (PhD)
In this thesis, the compact microstrip patch antennas in stacked configuration have been proposed. The microstrip patch antenna structure consists of a square patch with four equal u-shape on four sides of each patches. These structures provide an optimized patch area resulting in a substantial reduction in size compared to a typical microstrip square patch designed at the same frequency of operation. The characteristics of the antenna are obtained in terms of return loss, gain, radiation pattern and bandwidth and are compared with the conventional microstrip patch. The stacked configuration enhances both gain and bandwidth of the microstrip patch antenna at 2.45GHZ operating frequency. A size reduction of 70% is obtained along width 24.4dB gain and 6.6519GHZ bandwidth. The empire software is used to obtain the optimized performance of the proposed antenna. This antenna is found to be suitable for WLAN communications. Key Words: size reduction, stacked microstrip patch antenna, gain, bandwidth.
Analysis of Blind Adaptive Equalization Techniques for Audio Broadcast System
(Addis Ababa University, 2017-05) Amsalu, Tewodros; Hailemariam, Dereje (PhD)
The wireless channel, in general, and the audio broadcasting range in particular is prone to time dispersion, which causes inter symbol interference (ISI). This dispersive channel must be compensated (equalized) by making a communication system adaptive to the time varying properties of the channel. Practically, in digital audio broadcasting training sequences may not be available to implement the adaptation, which makes blind adaptive equalization methods more appropriate for such application. In this thesis the performance of three blind adaptive equalization techniques; namely, constant modulus algorithm (CMA), multi modulus algorithm (MMA) and fractionally spaced constant modulus algorithm (FS CMA) are investigated for application in audio broadcasting. This investigation is part of a joint project between Information Networks Security Agency (INSA) of Ethiopia and the Addis Ababa University (AAU) that intends to implement advanced digital receiver for a certain application. To capture the broadcasting environment three channel models are used. Moreover, 16-quadrature amplitude modulation (QAM) is considered for the simulation. Symbol error rate (SER), rate of convergence, stability, complexity and audibility are used as performance metrics. The simulation result shows that FSCMA has much better SER performance than CMA & MMA which provide 1 to 1.5 SNR advantages over the other two methods. The three equalizers are able to recover the transmitted audio bit streams when the channel do not introduce phase shift; MMA being the only method capable of recovering phase shift. On convergence, once the algorithms converged they stay stable until the channel condition start to change. Finally, it was noted that the three equalizers are able to equalize the received input data faster than the sampling rate of the audio signal. From all the simulation results, FS CMA has better or comparable performance than the CMA and MMA. Therefore, the thesis recommends FS CMA for implementation by INSA with the assumption that a separate unit will handle the phase recovery implementation. Analysis
Analysis of Electronic Attack Under Uav Platform Jamming
(Addis Ababa University, 2008) Getnet, Ashagrie; Roy, DP (Professor)
Ground base jammer cannot provide air space dominance for Ethiopia due to the massive highland complex of the country characterized by high rising mountains and dissected plateaus. In addition to this if high-flying systems and unsecured air space are piloted; it may be too dangerous in some situation to over fly certain areas. To overcome the above problem this thesis provides a good solution which is implementing a jammer on a UAV-platform. In this thesis, the Electronic Attack systems and the performance degradation of Surveillance Radar (P-15) due to UAV-platform jammer are described and analyzed. The jammer parameters were collected from simulation result as well as standards data. Using these parameters the effect of jamming on detection of targets is evaluated. The evaluation is performed by finding the change in radar SNR due to jamming and range reduction. The Predator-UAV type is the base system for this study much like the stand-off jammer. However, since the distance is closer to the radar, the EIRP jamming requirements are reduced. Stand-in jammer requires 6.3 watt at 50Km and stand- off jammer need 50 watt at 130Km from victim radar i.e. sufficient to jam P-15 Radar. For economical aspect stand-in jammer is much preferable for our country, since it provides 93% range reduction with a minimum amount of power.
Analysis of Energy Efficient Techniques for 5G Ultra Dense Wireless Communication Networks Using Massive MIMO
(Addis Ababa University, 2021-10) Halefom, Tswaslassie; Yihenew, Wondie (PhD)
In the modern wireless communication energy consumption becomes critical issue for wireless network operators. With the emergence of 5G wireless communication , the importance of energy efficiency (EE) has been appreciated since it is one of the significant performance analysis metrics of wireless networks. Energy can be saved in the design of wirless network if a proper analysis and design optimization is done. Massive MIMO and cell densfications are the latest encouraging technologies to maximize energy efficiency of 5G wireless communications. This thesis work mainly aims on the analysis of energy efficiency techniques of 5G wireless communication using Massive MIMO technology.The techniques to be analysis are in the precoding , in channel state information and massive MIMOtechnology. The analysis begins from circuit power consumption model using zero forcing precoding schemes with TDD communication protocol. The main design parameters are the number of massive antennas at the base station (M), the number of active user equipment terminals (K) , the system throughput (R) and cell density . Then EE is defined as the number of bits transferred per Joule of energy consumed. MATLAB tool is used to prove the impact of the main design parameters on energy efficiency. The impact of massive number of antenna , user equipments and system throughput on energy efficiency with perfect channel state information and imperfect channel state information is analyze . The simulation result shows that we can design optimal values of (M, K and R) that maximize energy efficiency of the system with perfect channel state information than imperfect channel state at the base station. The final results sows that zerforcing precoding and perfect channel state information at the base station saves more energy as compared to iperfect channel state information.
Analyzing Interference on Aviation Instrument Landing System from Frequency Modulated Broadcasting Systems: the Case of Bole International Airport
(Addis Ababa University, 2018-06) Roza, Shitu; Dereje, Hailemariam (PhD)
An Instrument Landing System (ILS) is a ground-based instrument approach system that provides precision guidance to aircrafts approaching and landing on a runway using combinations of radio signals. There are three components of ILS; namely, localizer (LOC), Glide slope (GP) and Distance Measuring Equipment (DME) or series of markers. LOC is used by the pilot to determine the location of the airplane relative to the centerline of the runway; GP provides the slope information (inclination angle) and DME distance from the beginning of the runway. Among the three ILS subsystems (components) this thesis focuses on LOC which is operating from 108.1 MHZ to 111.975 MHZ. This frequency range is prone to adjacent channel interference from Frequency Modulation (FM) broadcasting systems that are operating from 87.5MHZ to 108MHZ. In the past few years there is an increase in number of FM broadcasting radio stations in Addis Ababa. FM broadcasting stations are likely to cause intermodulation interference to the ILS LOC, hence, posing a great risk to aircraft navigation safety. This thesis addresses interference of Addis Ababa Bole international airport RWY 25 ILS localizers and analyzes the interference mechanism. The study accomplished through the establishment and implementation of models regarding the characterization of the transmitter and its signal, as well the definition of the aircraft approach path. Model development was done from the bases of field measurements of ILS LOC power level on a certain approach rout and then translates each parameter into defining the scenario. Furthermore, the assessments of interference were performed by using two criteria. One consisted on the raw analysis of the ratio between the LOC signal power and interfering signals power, and the other is based on an International Telecommunication Union (ITU) Recommendation. The results verified the non-existence of any harmful interference generated by Addis Ababa commercial FM broadcasting networks on ILS LOCs runway (RWY) 25 heading for the time being. However, the results also indicate that there is interference RWY 07, though it is not being operational for the time being.
Antenna Spacing E ects on Indoor MU-MIMO Channel Capacity
(Addis Ababa University, 2016-04) Endebu, Feyissa; Ridwan, Murad (PhD)
In theory, multi-user MIMO is more immune to most of propagation limitations plaguing single-user MIMO (SU-MIMO) systems, such as channel rank loss or an- tenna correlation. However, in this thesis work, it has been considered the e ect of antenna spacing on indoor multi-user MIMO sum-rate channel capacity at BS (base station) and user separation at UE (user equipment) side. This can be analyzed by using correlation based-analytical approximation method, and its simulation results. These simulation results were obtained using MATLAB simulation tools. The simulation result shows the comparison of correlated MU- MIMO sum-rate channel capacity for all scenarios considered with non-correlated stochastic channel capacity. Based on the result obtained it is better to use antenna spacing above 1 2 (half- carrier wave length) to get optimum correlated sum-rate channel capacity in in- door LOS compared to uncorrelated iid gaussian non-fading channel. In non-line of site(NLOS) MU-MIMO BC, antenna spacing from 1 5 to 1 2 is enough to get better sum-rate channel capacity than other correlated channel compared to uncorrelated Rayliegh fading channel capacity. Similarly, using Ricean fading channels, it is bet- ter to use antenna spacing above 1 2 to get optimum sum-rate channel capacity. KEY WORDS: MU-MIMO, Indoor Scenario, Antenna Spacing, User separa- tion, Sum-Rate Channel Capacity
Application of Smart Antennas to Cognitive Radio Systems
(Addis Ababa University, 2013-02) Murad, Ridwan; Mohammed, Abdo (Prof.); Eduard, Jorswieck (Prof.)
This dissertation studies three interrelated topics: design of non-uniform antenna arrays using genetic algorithm (GA), application of smart antennas to cognitive radio (CR) and determination of the distributions of signal-to-interference ratio (SIR) in Rayleigh fading. The performance of a single-element antenna is limited. To obtain high directivity, narrow beamwidth, low sidelobes, point-to-point and preferred-coverage pattern characteristics, etc., antenna arrays are used. Nowadays, antenna arrays appear in wireless terminals and smart antennas, so robust and e cient array design is increasingly becoming necessary. In array design, it is frequently desirable to achieve both a narrow beamwidth and a low sidelobe level. A uniform array yields the smallest beamwidth and hence the highest directivity. It is followed, in order, by the Dolph-Chebyshev and Binomial arrays. In contrast, Binomial arrays usually possess the smallest sidelobes followed, in order, by the Dolph-Chebyshev and uniform arrays. In the dissertation, GA is used to design a non-uniform linear array that approximates the beamwidth of a uniform array and having smaller sidelobe level than the Dolph-Chebyshev array. The designed array generally exhibits the largest directivity as compared to the uniform, Binomial and DolphChebyshev arrays. The result can be used in applications where narrow beamwidth and low sidelobes levels are preferred such as in switched-beam smart antennas. The second topic addressed by the dissertation is application of smart antennas to cognitive radios. Conventional CRs exploit the licensed spectrum by opportunistically seeking the underutilized radio resource in time, frequency and space (geographic) domains. However, there are other dimensions that need to be explored further for spectrum opportunity. The angle dimension is a typical example. The literatures surveyed point to the fact that little work has been done in this dimension. The dissertation particulary investigates the performance of CRs equipped with smart antennas in exploiting the angle opportunity in Rayleigh fading channel. The proposed cognitive transmitter keeps the interference to the primary receiver below a given threshold while at the same time ensuring high enough signal-to-interference-plus-noise ratio (SINR) at the cognitive receiver. It was shown that the angle spectrum can be signi cantly exploited for spectrum opportunity using smart antennas. It was also shown that the angle spectral e ciency for Rayleigh channel is lower as compared to a non-fading channel with the same power levels and radio terminal locations. Moreover it has been shown that increasing the cognitive transmitter power beyond a certain level has negligible e ect on the angle spectral e ciency. The third topic of the dissertation extends the determination of the distribution of SIN in Rayleigh fading channel when N interferers are present. In fading channels the SINR and SIR are random variables and their distributions have to be known for a correct description of the receiver. The distributions of SIR in Rayleigh fading have been described by deriving a closed form expression for the probability density function, cumulative distribution and outage probabilities.
Application of Spread Spectrum Time Domain Reflectometry for ADSL Fault Detection
(Addis Ababa University, 2021-05) Girma, Teshome; Ephrem, Teshale
The tremendous increase of interest in an increasingly expanding online world, access service providers face many unique challenges. Each and every subscriber are consistently demand more bandwidth to access video, gaming, and other online content at the same time multiple users demanding consistent performance from the fixed access network. To have more efficient ADSL technology, it wants to trace faulty points to avoid or reduce a loss so that a convenient technique has to be implemented. In copper cable communication, Time domain reflectometry or “Megger” technique was commonly used for characterization and fault location of copper cable transmission systems. TDR measures averaging so lacks accuracy in fault detection and a fault characterization will be done by low voltage, low impedance and echo based analysis. In TDR the analysis detection can be only suitable in short distance due to narrow pulse. ADSL line fault can be detected using TDR when the reflected signal generated due to impedance mismatch and electromagnetic discontinuity. Since fault detection using the classical Time Domain Reflectometry for ADSL technology is vulnerable for different noise, which results attenuation to locate the faulty point accurately. To overcome such problem, these study will implement distributed (SSTDR) fault detection means. Previously different researchers were analyzed and used this fault detection method in order to overcome fault location problem and to enhancing accuracy within a minimal power threshold. Distributed SSTDR fault detection means have been implemented as an operative fault detection technology aimed at finding distorted fault points on aircraft wires. The optimization and fault detection for ADSL technology is done using correlation algorithm by analyzing and correlating the incident signal with reflected signal with bigger bandwidth and kasami sequence generator was used in the simulation and modulated with sine wave and spreaded over the transmission line and despreaded before cross correlation is done. Incident signal and reflected signal is analyzed using correlation function and the maximum peak will determine the fault status and its location. Finally, different form of fault sparked and the fault determined based on the reflected signals. Basic verification parameters are power, signal to noise ratio and distance. This research shows a progress in locating a defect point compared to the classic TDR fault detection techniques for ADSL technology.
Asphalt Pavement Thickness Estimation and Material Characterization
(Addis Ababa University, 2019-01) Tewodros, Mulugeta; Ephrem, Teshale (PhD); Mequanent, Mulugeta (Mr.) Co-Adviser
Asphalt pavement is one of the most dominant infrastructure consuming huge investment and play as a blood vessel to a nation. The surface layer of asphalt pavement is a multilayer structure. It commonly has three sub-layers: the top surface layer (Asphalt), the intermediate surface layer (Base course) and the following surface layer (Sub base). The thicknesses of the surface layer and the top surface layer have great importance on quality condition and maintenance of asphalt pavements. Estimating asphalt pavement layer thicknesses and material type accurately helps to evaluate the pavement condition. Common methods of estimation of these parameters includes boring a hole (coring) at selected sampling points, used to estimate the asphalt layer thicknesses and material characterization, have limitations. Ground Penetrating Radar (GPR) represents an alternative non-destructive approach which alleviates some of this limitation. GPR signal processing is a non-destructive technique, particularly promising for pavement characteristics interpretation. The accuracy of asphalt pavement layer thicknesses estimation and material characterization depends on GPR data analysis employing different estimation approaches and based on the incoming signal from the radar. The focus of the thesis is to investigate asphalt pavement thickness and material characterization using GPR data. Finite Difference Time Domain (FDTD) simulation and GPRmax are tools used to validate the research. This has to be taken seriously.
Bandwidth and Gain Performance Comparison Of Rectangular-Patch Microstrip Antenna (RMSA) And Coplanar Waveguide (CPW) Rectangular-Patch Antenna
(Addis Ababa University, 2011-01) Abiy, Bekele; Mohammed, Abdo (PhD)
In today’s world, microstrip antenna and coplanar waveguide patch antenna are used in all wireless communication such as cellular telephony, satellite, portable personal communication, aircraft, spacecraft, and missile applications. The growth and popularity of wireless application is quite dominant because of its mobility, the demand for high speed transmission of large data, customer request for multi-media service, and the need for new technologies, as well. This shows that there is a large investment that has been put in to wireless communication by major companies in the telecommunication industry. WLAN is one part of the investment that gains an increase in its usage because it provides high quality of services with low cost to more users. The IEEE 802.11 workgroup currently use three frequency ranges 2.4 GHz, 3.6 GHz and 5 GHz for WLAN technologies. Each range is divided into a multitude of channels. Countries apply their own regulations to both the allowable channels, allowed users and maximum power levels within these frequency ranges [1].
Bandwidth Improvement of Microstrip Antenna Using Log Periodic Technique
(Addis Ababa University, 2008-03) Maare, Mekonen; Mohammod, Abdo (PhD)
The thesis covers two aspects of microstrip antenna designs. The first is the analysis and design of single element narrowband rectangular microstrip antenna which operates at the central frequency of 2.4 GHz and the second aspect is the design of five element broadband Log Periodic microstrip antenna. Both antennas have been modeled, designed and simulated. Basically, transmission line and cavity modeling are going to use to model both antennas. First, the design parameters for single element of rectangular patch antenna have been calculated from the transmission line model equation and extend the antenna design to five element log periodic microstrip antenna using log periodic analytical technique. The simulation process has been done through momentum simulation using Empire software. Each data from the Finite Difference Time Domain Method (FDTD) simulation extract and combine with the microstrip transmission line. The rectangular microstrip antenna design uses Flame Retardant 4, FR4, microstrip board with dielectric constant 4.7, scaling factor 0.95 and loss tangent is 0.019. The properties of antenna such as bandwidth, S parameter has been investigated and compared between a single element rectangular and a five element log periodic rectangular microstrip antenna. .
Big Data Analytics for Prediction of Mobile Users Movement using Neural Networks
(Addis Ababa University, 2019-06) Selamawit, Engliz; Yihenew, Wondie
The rise of data warehouses and the rise of multi-media, social media and the Internet of Things (IoT) generate an increasing Volume of structured, semi-structured and unstructured data. Towards the investigation of these large Volumes of data, Big Data and data analytics have become emerging research ﬁelds attracting the attention of academia, industry and governments. Researchers, entrepreneurs, decision makers and problem solvers view ‘Big Data’ as an important tool used to revolutionize various industries and sectors, such as business, health-care, retail, research, education and public administration. In this context, a general view on analysis of Big Data, especially in telecommunications industry is proposed. In order to allocate scarce resources eﬃciently the location of mobile users should be predicted. So, this work focuses on analysis of data for mobile users movement prediction in telecommunications network. The objective of this work is to process and analyze obtained samples of OpenCelliD data by means of Neural Network and provide as accurate mobile users movement prediction as possible. More speciﬁcally, Modiﬁed Levenberg-Marquardt (LM) algorithm is presented as an eﬀective algorithm for movement prediction. Obtained result from prediction is optimized by iteration method designed for ﬁnding the best possible combination of Neural Network parameters. Eﬃciency of mobile users movement prediction is veriﬁed by simulation in Matrix Laboratory (MATLAB). Simulation results show suﬃcient accuracy for wide use of prediction for mobile networks optimization or services exploiting prediction of mobile users movement. Measured results fully reﬂect real solution for telecommunications industry and can help to plan activities connected with mobile users movement in a given area.
Coding and Decoding of perfect Space-time Block Codes: Analysis and Performance Evaluation
(AAU, 2012-11) Aregawi, Gebresilassie; Hailu, Ayele (PhD)
Multiple-input multiple-output (MIMO) is one of the most significant advances in digital communication which enabled to increase the data rate as well as improve the reliability and robustness of the system to as compared to single antenna systems. This is achieved by deploying multiple antennas both at the transmitter and receiver sides [1]. However, various assumptions about channel state information (CSI) and channel fading lead to different capacity results [2]. Fading can be reduced substantially by using diversity techniques. Space-time diversity is the most economic technique. Space-time block codes (STBCs) are the most widely employed space-time codes. Perfect space-time block codes (PSTBCs) are families of STBCs that satisfy all of the following criteria: full diversity, high rate, good constellation shaping, uniform average transmitted energy per antenna, nonvanishing determinant (NVD) for increasing spectral efficiency and diversity-multiplexing tradeoff (DMT). In this thesis, we investigate and demonstrate the coding and decoding of PSTBCs. We first give the design criteria of STBCs followed by the mathematical background of cyclic division algebra (CDA) as a constructing tool for PSTBCs. The PSTBCs are constructed and investigated to be the most efficient family of STBCs by the design criteria of STBCs. Having considered conditional optimization maximum likelihood (COML) as a near optimal yet less complex decoding scheme of PSTBCs, we demonstrated the decoding of Golden code, a family of PSTBC, as an example. Simulation results show that the symbol error rate of the COML decoding of the Golden code is almost equal to ML decoding with decoding complexity of only 2 which is the order of, V 4 for the conventional ML. Further, we considered the performance of the COML decoding under transmit, receive and both transmit and receive antenna correlations and found consistent complexity reduction. Although there is some deviation, in exact optimality of the COML decoding of the Golden code as of the previous works in the literature, which arise most probably due to the inaccuracy of the QAM quantization we used in this thesis, we conclude that an antenna PSTBC is near optimally COML decodable with a reduction in complexity of the order, from its respective ML.
Comparative Analysis of Blind Spectrum Sensing Techniques over Fading Channel
(Addis Ababa University, 2018-12) Milkias, Hailu; Murad, Ridwan (PhD)
A spectrum is a scarce and precious natural resource and a matter of concern with the rapidly growing wireless communications. However, studies show that licensed spectrum is underutilized. Cognitive radio system allows unlicensed users also called secondary users to access licensed spectrum band also known as spectrum hole of primary user when they are not occupied. To do this the secondary users need to continuously monitor the licensed user’s activity to find the unused band. Spectrum sensing is the key task for cognitive radio which prevents the unwanted interferences with authorized users to recognize available radio spectrum and enhance the usage of spectrum. Spectrum sensing is also a tough task because of shadowing, fading, and time-varying nature of wireless channels. This thesis investigates the difference in performance of energy detection and eigenvalue based blind spectrum sensing techniques (without having prior knowledge) by implementing it over different environmental models and compares the Receiver Operating Characteristics (ROC) curves. Evaluation and analysis of performance is done by using Monte Carlo method with MATLAB software. The implementation gives detail comparison between blind spectrum sensing technique performances over fading channel and multiple network nodes. In particular, the result shows the minimum required energy level for optimal detection (with acceptable interference) over fading channel and also how effectively cooperative
Comparative Analysis of Non-Blind Algorithms on the basis of Sidelobe Level for Smart Antenna System
(Addis Ababa University, 2018-07) Seid, Ahmed; Murad, Ridwan (PhD)
From time to time the need for good quality communication is required in different aspects of life. Many challenges can face service providers for implementing different communication facilities. One of these great challenges is the limitation of available radio frequency. So it is mandatory to use the scarce resource most efficiently in parallel with providing good quality of service for the customers. One of the way, for efficient utilization of limited radio frequency (RF) spectrum is to use smart antenna system. Smart antenna radiates not only narrow beam towards desired users exploiting signal processing capability but also places null towards interferers, thus optimizing the signal quality and enhancing capacity. The efficiency of the smart antenna can depend on different parameters like angle of separation between the desired and the interferer signal, the number of elements of the array and the spacing between the array elements. Different researches showed that the performance of smart antenna can be improved by using an array with a relatively large number of elements having an optimum spacing between them with a relatively large angle of separation between the desired and the interferer signal. The central aim of this thesis work is comparing the performance of smart antenna in terms of reducing radiation in unintended direction. This is achieved by using an algorithm that produces lower sidelobe level in the radiation pattern of the antenna. Comparative analysis of three nonblind algorithms, Least Mean Square (LMS), Sample Matrix Inversion (SMI) and Recursive Least Square (RLS), on the basis of Sidelobe Level (SLL) is studied in this thesis work. Smart antenna incorporates these algorithms to calculate complex weights according to the signal environment. Simulation results reveal that all the three algorithms have their own beamforming characteristics. But the LMS produces lower sidelobe level as compared to the other two algorithms. Therefore, the LMS algorithm is found the most efficient because of its simplicity, lower complexity and sidelobe level for communication through a flat fading channel. In addition, as the number of elements increases, the sidelobe level of array factor pattern decreases for the case of LMS algorithm.
Comparative Analysis of QoS in MPLS and IP Network for Broadband Intelsat Internet Using Riverbed Modeler Academic Edition
(Addis Ababa University, 2018-08-22) Erena, Keno; Mohammed, Abdo (Prof.)
Nowadays Multiprotocol Label Switching (MPLS) and Internet Protocol (IP) are widely used technologies in service providers and enterprise networks across the globe. In this thesis, the behavior of traffic in both IP and MPLS are studied since they have more advantageous through all network models. MPLS -enabled infrastructure has the ability to transport any type of payload (Asynchronous Transfer Mode, frame relay, and Ethernet) over it, within the same time providing a multipurpose architecture. An incoming packet is arranged only once as it enters into the MPLS domain and gets assigned label information. Then after all decision processes along a specified path is based upon the attached label rather than assigning destination IP addresses. This work also presents the design and simulation of MPLS and IP network for different applications. These applications used for the performance evaluation including voice, File Transfer Protocol (FTP) and Hyperlink Text Transfer Protocol (HTTP). The parameters used for the analysis are throughput, link utilization, packet delay, jitter, page response time and FTP response time. Comparative analysis of the quality of services is a set of performance models to evaluate the different combination of IP and MPLS network routing topologies have been explained for the proposed network model. The results obtained from this study shows how a service provider can benefit from MPLS services with increasing network performance like throughput, mean opinion score, a packet sent and received. Comparing MPLS queuing delay results with the IP result from the shortest path routing scenario network, the queuing delay keep a much less queuing delay in MPLS configuration with value (Maximum 0.00002 seconds and Minimum 0.00001 seconds) between Http Client and ISP Branch 1. It can be observed that the queuing delay MPLS scenario is more balanced between both paths comparing it with IP scenario.
Comparative Performance Analysis of Free Space Optics as a Backup Link for Fiber Connectivity around the Areas of Bole Medhanialem Using Optisystem 15
(Addis Ababa University, 2021-05) Melat, Ambaye; Yihenew, Wondie (PhD)
Free space optics (FSO) is a field of curiosity and importance for the scientists because of its numerous applications and advantages like low cost, easy deployment, high data rate, secure links and license free bands. FSO technology utilizes the light propagating in the free space to transmit the data wirelessly for both telecommunications and computer networking domains. In optical communication, we use optical fiber cable as a medium but in the free space optical communication, we use the free space as the medium to propagate the light signal [1]. Even if fiber optics is the most reliable means of providing optical communications, the digging delays and associated costs to lay fiber often makes it economically prohibitive. A telecom service provider in our case Ethiotelecom faced a problem to deliver a quality service because of many technical issues one of them is lack of deploying a redundant link. As we all know unable to deliver a promised service leads to customer dissatisfaction. This thesis paper proposes a design of point to point FSO as a backup link for fiber connectivity around the area of Bole Medhanialem pointing from Bole exchange to three different enterprise buildings (Sapphire Addis Hotel, Best western Addis Hotel, Skylight Hotel) that is capable of transmitting data at 80Mb/s, 60Mb/s and 200Mb/s for a distances of 0.116km, 0.36km and 1.45km respectively. And it’s performance analysis and comparison with fiber optics observed using Optisystem software15 by taking the performance metrics Q factor and BER found from the reading of BER analyzer. From the results it has been understood that FSO link can perform like FO (main link) at a cost of input power. Since FSO link in Ethiotelecom infrastructure has not been studied before we can take this paper as a reference for future deployment of FSO technology in the country.
Comparative Performance Analysis of Modulation Formats for 5G Wireless System
(Addis Ababa University, 2019-06) Fikreaddis, Tazeb; Dereje, Hailemariam (PhD); Amare, Kassaw (MR.) Co-Advisor
The fourth generation (4G) of cellular networks, was initially roll out in 2009/10 by succeeding third generation (3G). The fth generation (5G) is the forthcoming evolution of mobile technology expected to be used by 2020 with a wide range of services and usability beyond the use of 4G [1] [2]. Three main services, enhanced Mobile Broadband (eMBB), Ultra-reliable Low-latency Communication (URLLC) and massive Machine Type Communication (mMTC) will impose di erent requirements on the 5G air interface [2]. Orthogonal Frequency Division Multiplexing (OFDM) have been the most attractive one for the development of wireless communication system like 4G due to several advantages like ease of implementation, immunity to interference, high data rate etc. Whereas 5G will demand more from physical layer than the current OFDM can deliver. Therefore, more waveforms have been proposed to address the challenges of OFDM. In this thesis, we provide analysis and comparison for the candidate waveforms Filterbank multicarrier (FBMC) and Universal- ltered multicarrier (UFMC). To obtain insightful analysis we will not only introduce the basic principle of the waveforms but also reveal the characteristics of each waveforms. Moreover, performance comparison in terms of Power spectral density (PSD), Bit error rate (BER) and spectral e ciency presented. Also computational complexity of waveforms in di erent cases evaluated. Mathematical analysis and characterizations are validated by computer simulation employing Mathlab. The result shows advantages and drawbacks for each modulation schemes. FBMC shows the best spectral leakage among both waveform candidates. This reveals to be almost insensitive to multiuser interference to support di erent use cases with in same bands. UFMC, reveals to be most promising which close to OFDM with advantage of better out-of-band (OoB) emission. Finally, some concepts which should addressed are underlined.
Comparative Study of Machine Learning Techniques for Path Loss Prediction
(Addis Ababa University, 2023-11) Ademe Wondimneh; Dereje Hailemariam (PhD)
Path loss is the term used to describe the difference in signal strength between transmitted and received. Predicting this loss is a crucial task in wireless and mobile communication to gather data for resource allocation and network planning. Deterministic and empirical models are the two fundamental propagation models that are used to calculate path loss. There is a trade-off between accuracy and computing complexity between these models. Machine learning models reflect a classic conflict between accuracy and complexity and have significant potential in path loss prediction because they can learn complicated non-linear correlations between input properties and target values. This study investigates the application of machine learning techniques for path loss prediction in Addis Ababa LTE networks. Artificial neural networks (ANNs), random forest regression (RFR), and multiple linear regressions (MLR) are employed as machine learning models and compared with the widely used COST 231 empirical model. Data for training and testing is obtained through measurements from Addis Ababa LTE networks. The performance of the proposed models is evaluated using statistical metrics such as root mean squared error (RMSE), mean absolute error (MAE), and R-squared (R2). The results demonstrate that the RFR model outperforms the other models in terms of prediction accuracy, achieving an MAE of 3.48, an RMSE of 5.35, and an R2 of 0.77. The ANN model also exhibits satisfactory performance with an MAE of 4.19, an RMSE of 5.78, and an R2 of 0.71. The Cost 231 model, on the other hand, exhibits lower prediction accuracy. In terms of computational complexity, ANNs are found to be the most computationally intensive, while MLR is the simplest model among the evaluated machine learning models. RFR falls between ANNs and MLR in terms of computational complexity.
Comparative Study on Bandwidth Enhancement Techniques of Microstrip Patch Antenna
(Addis Ababa University, 2008-01) Hailu, Zewdu; Abdo, Mohammed (PhD)
Conventional microstrip antennas in general have the attractive features such as low profile, light weight, easy fabrication, and conformability to mounting hosts. However, microstrip antennas inherently have a narrow bandwidth, low gain, and bandwidth enhancement is usually demanded for practical applications. In addition, applications in present-day mobile communication systems usually require smaller antenna size in order to meet the miniaturization requirements of mobile units. Thus, size reduction and bandwidth enhancement are becoming major design considerations for practical applications of microstrip antennas. For this reason, conducting studies to achieve compact and broadband operations of microstrip antennas is thought to be very important. The purpose of this thesis is to make a comparative study on the techniques that help to overcome the bandwidth constraint of microstrip patch antennas and to propose the better technique by taking different consideration such as the antenna gain, bandwidth and related issues. In this thesis work broad banding techniques like using feeding techniques (proximity coupled), stacked patches, parasitic arrangement of patches and the use of different shapes (i.e. E-shaped) are studied. The bandwidth obtained for each type of the antenna are 10.8%, 11.5%, 15.6% and 25.6% respectively with respect to the operating frequency of each of the antennas. The result shows that the E-shaped patch antenna has better performance. Key Words: patch antenna, return loss, bandwidth, gain

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