Electrical Computer Engineering
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Item PERFORMANCE ANALYSIS OF HYBRID OPTICAL FIBER/FSO COMMUNICATION SYSTEM USING ADVANCED MODULATIONS(Hawassa University, 2021-04-21) FISEHA ZELALEMDue to its lower attenuation and high bandwidth, current telecommunication infrastructure uses optical fibers for high data long haul transmission. Free space optics (FSO) technology is a good option for short-distance multi-gigabits per second or beyond data transmission. Nowadays, it has different application areas such as indoor, outdoor, underwater, and deep-space communications. A key area within this new generation is the combination of optical fiber and FSO network to provide high bandwidth for both long and short-distance services. The hybrid link uses coherent optical advanced modulation and dispersion compensation techniques to achieve the best performance with the existence of atmospheric turbulence effect and fiber limitations. Orthogonal frequency division multiplexing (OFDM) and dual-polarization quadrature phase-shift keying (DP-QPSK) are considered promising technologies to satisfy the demand for bandwidth expansion in broadband services. OFDM can overwhelm optical fiber limitations such as polarization mode dispersion (PMD) and chromatic dispersion (CD), whereas DP-QPSK provides good noise immunity. This thesis concentrates on designing, simulation, and performance analysis of 100Gbits/s data rate hybrid optical fiber/FSO systems using coherent optical OFDM and DP-QPSK modulation techniques. MATLAB software and OptiSystem simulation tool are used to design and simulate the hybrid system. To study the performance of the systems and the quality of the signals the bit error rate and the Q-factor are considered. As a result, for 100Gbits/s per channel with DP-QPSK based system, the link coverage is up to 468m in FSO and 202km by fiber cable; and up to 510m FSO link and 220km by fiber optics for CO-OFDM system. It is observed that the CO-OFDM system has high tolerance against linear signal distortion effects and sensitive to nonlinear effects which affects the system performanceItem PERFORMANCE COMPARISION OF PILOT-BASED CHANNEL ESTIMATION METHOD IN OFDM SYSTEM OVER FADING CHANNEL(Hawassa University, 2019-10-11) HABTAMU ABEBEWireless channel is unknown and inclined to time dispersion, which causes inter symbol interference (ISI) and fading. OFDM is one of the most capable core technologies in the fourth generation of wireless communication systems. OFDM has the advantage over the conventional single-carrier modulation schemes when the channel is frequency-selective fading and widely used in current wireless networks. In this thesis work the performance of two pilot-based channel estimation algorithms; namely, least square (LS) and Minimum Mean Square Error (MMSE) with corresponding channel interpolation technique is investigated for digital communication systems. Channel estimation is a technique that can be used to design a channel in a particular surrounding based on known train symbols which is inserted in the input of transmitter end and tested at the receiver end. This thesis performs , analysis of channel estimation algorithms based on bit error rate (BER) and signal to noise ratio (SNR) minimizing the error distance between the transmitted and received data. To estimate the channel coefficients; The MATLAB plot can perform for QAM, 16QAM, and 64QAM constellations. For different international telecommunication union (ITU) channel models Such as, the portable outdoor (PO), portable indoor (PI), Rural Area six path (RA6), Typical Urban six path (TU6), and Rayleigh channel models. Typical urban channel model has better at higher order modulation. From the MATLAB results, LS and MMSE algorithms are compared based on their pilot ratio and channel length. LS estimation has better at high SNR value compared to MMSE estimation.Item Performance Analysis of Modulation Techniques for 5G Networks(Hawassa University, 2018-03-17) GETACHEW HAGOSThe new 5G cellular network systems will feature several innovative strategies as compared to existing LTE systems, such as extensive adoption of small cells, use of mm-wave communications for short-range links, large scale antenna arrays installed on macro base stations, cloud-based radio access network, cognitive radio etc. All these strategies will be impacted by the modulation format used at the physical layer. At the same time, 5G cellular networks will have more stringent requirements than LTE in terms of latency, energy efficiency and data rates, which again are impacted by the adopted modulation scheme. Hence, proper selection and utilizing efficient modulation scheme is critical. The current modulation technique such as orthogonal frequency division multiplexing (OFDM) suffers from high peak to average power ratio which results in low efficiency of power amplifier and increases the battery consumption. Moreover, the OFDM spectrum has high out of band side lobes or side lobe leakage causing problem of low spectral efficiency. Therefore, OFDM can fulfill the requirements of 5G wireless networks in a limited way. In order to overcome some of these drawbacks of OFDM, new modulation techniques for 5G communication systems are considered. Among them, Filter bank multicarrier (FBMC), and Universal filtered multicarrier (UFMC) are expected be in race to be considered for the selection. In this paper, we perform the performance analysis of OFDM, UFMC, and FBMC in terms of its spectral efficiency (SE), power spectral density (PSD), peak to average power ratio (PAPR), and bit error rate (BER) using the MATLAB software tools. We analyze the results by varying the parameters of the modulation techniques which affects the performance of OFDM, UFMC, and FBMC. The plot shows that, FBMC has better SE for large burst durations but for small burst duration the SE of UFMC is better. In terms of PSD and BER FBMC is better. In terms of PAPR UFMC is better. The result of this research will play a significant role in selecting efficient modulation scheme for the upcoming 5G cellular networksItem PERFORMANCE COMPARISION OF PILOT-BASED CHANNEL ESTIMATION METHOD IN OFDM SYSTEM OVER FADING CHANNEL(Hawassa University, 2019-08-20) HABTAMU ABEBEWireless channel is unknown and inclined to time dispersion, which causes inter symbol interference (ISI) and fading. OFDM is one of the most capable core technologies in the fourth generation of wireless communication systems. OFDM has the advantage over the conventional single-carrier modulation schemes when the channel is frequency-selective fading and widely used in current wireless networks. In this thesis work the performance of two pilot-based channel estimation algorithms; namely, least square (LS) and Minimum Mean Square Error (MMSE) with corresponding channel interpolation technique is investigated for digital communication systems. Channel estimation is a technique that can be used to design a channel in a particular surrounding based on known train symbols which is inserted in the input of transmitter end and tested at the receiver end. This thesis performs , analysis of channel estimation algorithms based on bit error rate (BER) and signal to noise ratio (SNR) minimizing the error distance between the transmitted and received data. To estimate the channel coefficients; The MATLAB plot can perform for QAM, 16QAM, and 64QAM constellations. For different international telecommunication union (ITU) channel models Such as, the portable outdoor (PO), portable indoor (PI), Rural Area six path (RA6), Typical Urban six path (TU6), and Rayleigh channel models. Typical urban channel model has better at higher order modulation. From the MATLAB results, LS and MMSE algorithms are compared based on their pilot ratio and channel length. LS estimation has better at high SNR value compared to MMSE estimation