Computer Engineering

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http://etd.aau.edu.et/handle/123456789/48

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Browsing Computer Engineering by Author "Adugna, Eneyew"

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    High Performance Automatic Target Recognition
    (Addis Ababa University, 2012-10) Tadesse, Misiker; Adugna, Eneyew
    Designing a vision system, which was motivated by that of the human eye, has been done since the introduction of digital computing devices. Due to its abundant applications, this area is a hot topic in the industry. Its computational complexity hinders it from the required accuracy and flexibility achievable by these systems. The evolution of processing technology has given to the birth of parallel processing units such as Graphics Processing Unit (GPU) and Field Programmable Gate Array (FPGA). Using these parallel processing units Data Intensive applications can be done in parallel to get a performance speedup with lower implementation cost, unlike Application Specific Integrated Circuits (ASICs). In this thesis, a real-time Automatic Target Recognition system having the ability of detection, identification and tracking of pre-specified targets even with bad visual artifacts that could originate from lightning conditions, environmental conditions or other noise generating circumstances is developed. This thesis work investigates an improved combination of detection and recognition algorithms to reach a better solution to the problem of target detection and recognition while aiming to fit the design of a minimal system. For each algorithm involved the theoretical background is investigated and a detailed description of the realization is given followed by an analysis of both achievements and short comings of the design. A speed up of 2.4 is achieved, by using a non-preeminent GPU, over brute force implementations.
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    Performance Evaluation of Least Mean Square Error (LMS) and Blind Adaptive Algorithm In Suppressing Multiple Access Interference in CDMA Receiver
    (Addis Ababa University, 2011-08) Taye, Demissu; Adugna, Eneyew
    Direct sequence code division multiple access (DS-CDMA) is a high capacity air interface as compared to time division multiple access (TDMA) and frequency division multiple access (FDMA). This system is more resistant to jamming and unintended listener. In this access technique more than one user access the same frequency band width at the same time. The main limitation of this system is that, the signal quality of the intended user degrades as the number of users increases that result in multiple access interferences (MAI). So, in this thesis adaptive algorithms are used in CDMA receiver for suppressing multiple access interference (MAI). Two families of adaptive algorithms namely, least mean square error (LMS) and constant modulus blind adaptive algorithms are used. The schematic representation of each of the two algorithm receiver is developed, and on which the simulation analysis was based. The LMS adaptive algorithm requires training sequences for its adaptation where as the later does not require any training sequences, instead needs appropriate initialization of tap weights. The performance of these adaptive algorithms in suppressing multiple access interference (MAI) was found to outperform matched filter receiver but they performs less than decorrelating detector receivers. From the simulation result the decorrelating detector achieve 10-2 BER around 10.5dB SNR whereas LMS and CMA achieve this BER around 12.5dB and 16dB SNR respectively. The matched filter cannot achieve this BER within 20dB SNR. From the result we can deduce that decorrelating detector is an optimal receiver that almost eliminates multiple access interference. In addition to this it was found that the BER performance of LMS receiver is much better than the CMA receiver. It was also shown that under perfect synchronization Walsh-Hadamard sequence can completely eliminate MAI due to their orthogonal nature. As the spreading gain of the spreading codes is higher, their ability to reduce MAI also increases which is at the cost of band width. Key Words: CDMA, LMS algorithm, CMA, decorrelating detector, matched filter receiver.