DSpace Collection: Thesis - Communication Engineering

SIMULATION OF FLIGHT FOLLOWING SYSTEM

Tue, 27 Nov 2012 05:53:39 GMT

Title: SIMULATION OF FLIGHT FOLLOWING SYSTEM

Authors: Mathewos, Essatu

Abstract: 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 transmission 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. The principle of operation of the simulation of flight following system is discussed in section 6 and in section 7 conclusion and improvement using the same system for other forms of data are presented.

Synthetic Speech Trained - Large Vocabulary Amharic Speech Recognition System (SST-LVASR)

Thu, 03 May 2012 21:59:53 GMT

Title: Synthetic Speech Trained - Large Vocabulary Amharic Speech Recognition System (SST-LVASR)

Authors: Mesfin, Birile Woldetsadik

Abstract: Amharic is the official language of Ethiopia, which is characterized by very large morphological forms of words. This thesis is an investigation of the possibility of developing an Automatic speech recognition system (ASR) for Amharic using synthesized Amharic speech generated through concatenation of prerecorded morphemes, can be used to train a hidden markov model (HMM) based ASR system. The development of HMM based ASR system requires identification of all possible words and a construction of text and speech corpora containing multiple samples of the words to be recognized by the system. These data are then used as training sets in the development of the models, the final objective being the construction of HMM models for each recognition unit. Since there are a large number of morphological forms for the words in Amharic, the effort of collecting the Amharic words for constructing the text corpus and the recording and labeling of the same words for the speech corpus is extremely difficult. This thesis demonstrates that by developing an automatic morphological expander, the effort of developing the text corpus is reduced to a manageable level. Additionally, a significant reduction in the speech corpus development is achieved by using machine generated speech for training the HMM models of the ASR system. These reductions in the development efforts of the text and speech corpora greatly reduce the most prominent of the obstacles in developing a general purpose Amharic speech recognizer. The 62.37% word accuracy for naturally recorded speech indicates that using synthetic speech for training at least 62% of the words are correctly identified and suggests that with synthetic speech some level of recognition is possible, giving the imputes for more research in finding ways to increase this accuracy.

PERFORMANCE ANALYSIS OF SPACE TIME CODING ON MIMO AND COOPERATIVE DIVERSITY SYSTEM

Thu, 03 May 2012 13:43:22 GMT

Title: PERFORMANCE ANALYSIS OF SPACE TIME CODING ON MIMO AND COOPERATIVE DIVERSITY SYSTEM

Authors: DEREJE, GIRMA

Abstract: In a wireless network, users can relay information to exploit cooperative diversity, thereby increasing reliability. The uses of multiple transmit and receive antennas (MIMO) can help to exploit transmit and receive diversity respectively. This thesis discusses the application of a technique called space time block coding (STBC) on a system based on the joint use of cooperative diversity and MIMO schemes, which we hope intuitively that the system performance can be increased further. A source node, equipped with two transmits antennas, first encodes incoming data using STBC and then broadcasts the resulting code to relay and destination nodes. Then, the two relay nodes, each equipped with single antenna, either amplify-and-forward (AF) or decode-and-forward (DF) the received codes to the destination. The destination node combines (e.g., using maximum ratio combining signal in order to recover the original data. As the signals from the source and relay are received through different paths, which are assumed to be spatially independent, spatial diversity can be exploited. Compared with point-to-point transmission system and simple Alamouti STBC system with no relays, AF based STBC system obtains one additional benefit, achieving spatial diversity offered by the relays. Moreover, the STBC-based DF cooperative system has two additional benefits. First, it achieves the spatial diversity offered by the relay channel and secondly, it has the ability to introduce the characteristics of STBC into the relay system. In addition, the system model and performance evaluation of these systems in various channel conditions and modulations (using simulation) will be addressed.

STABILIZATION OF LIGHT GREY AND RED CLAY SUBGRADE SOIL USING SA-44/LS-40 CHEMICAL AND LIME

Fri, 17 Oct 2008 13:36:17 GMT

Title: STABILIZATION OF LIGHT GREY AND RED CLAY SUBGRADE SOIL USING SA-44/LS-40 CHEMICAL AND LIME

Authors: Yohannes Argu

Abstract: ABSTRACT This study is undertaken on a light grey (expansive) and a red clay soil samples taken from within Addis Ababa. The change in engineering properties of these soils treated with SA- 44/LS-40 chemical alone, lime alone and combinations of both at different application rates are investigated. The investigation of the modifications in engineering properties of the stabilized soils are made using laboratory tests that include soaked CBR and CBR swell tests, swelling pressure test, Atterberg limit tests, percent swell test and free swell tests. The modifications in engineering properties were evaluated after curing the treated sample for fourteen days. From the study, it is observed that the application of lime alone and SA-44/LS-40 chemical with lime shows improvements of varying degree on the engineering properties of both the light grey and the red clay soils. However, no specific mix ratio showed the maximum improvement in all the engineering properties of each soil. This suggests that before deciding for large-scale applications, the desired improvement level of the engineering properties of a particular soil should be specified first, and tests be conducted for different mix ratios to arrive at the optimum one.

Description: A Thesis submitted to School of Graduate Studies of Addis Ababa University In Partial Fulfilment of the Requirements for the Masters Degree of Civil Engineering in Geotechnical Engineering