البحث — المستودع الرقمي العراقي

المستخلص: The internet revolution has created the need for wireless technologies that can deliver data at high speeds in a spectrally efficient manner. However, supporting such high data rates with sufficient robustness to radio channel impairments requires careful selection of modulation techniques. The demand for high - speed mobile wireless communications is rapidly growing. OFDM technology promises to be a key technique for achieving the high data capacity and spectral efficiency requirements for wireless communication systems. Abstract In this thesis, Inverse Discrete Wavelet Transform (IDWT) is used as a modulation technique instead of Inverse Fast Fourier Transform (IFFT) with coded OFDM due to its excellent orthogonality and superior spectral containment properties of wavelet filters. Coded Orthogonal Frequency Division Multiplexing (COFDM) is the same as OFDM except that forward error correction is applied to the signal before transmission. This is to minimize errors in the transmission due to lost carriers from frequency selective fading, channel noise and other propagation effects. Convolutional code is used in this thesis as a forward error correction code. The proposed (DWT - COFDM) system is simulated under the effect of additive white Gaussian noise channel, and multi - path fading channel at different values of Doppler frequencies (22.2Hz, 41.7Hz and 444.4Hz) which are the most significant impact channel parameters on the bit error rate performance. The proposed system is also compared with DWT - OFDM, FFTCOFDM and FFT - OFDM systems. It is found that the proposed system can significantly improve the BER performance and it performs better than the other three systems. On the other hand, convolutional code and DWT is used to reduce the peak to average power ratio (PAPR) which is considered the serious problem in any wireless communication system using multi carrier modulation techniques like OFDM systems by using two of the most important non distortion techniques which are selective level mapping (SLM) and partial transmit sequence (PTS) and the results show that the proposed systems for SLM and PTS techniques can perform better than the conventional SLM and PTS. The results also show that the proposed PTS technique performs better than the proposed SLM technique.

تصميم الترميز الكتلي المكاني الزماني لتقنية الموجة الواسعة اللاسلكية عريضة النطاق باستخدام مويجات التحويل المنفصلة == Design Of Space Time Block Coding Of WIMAX System By Using DWT

اسم المؤلف: رسل نوري سعید

اسم المشرف: ليث علي عبد الرحيم

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2013

الموضوع الدقيق: هندسة الكهرباء

الدرجة: ماجستير

الجامعة: جامعة بابل - كلية الهندسة - قسم الهندسة الكهربائية

اللغة: الانكليزية

مكان الجامعة: بابل

الصفحات الاولى:

انتقال الموجات الاجهادية المرنة - اللدنة في الاضلاع الموشورية واللاموشورية باستخدام طريقة الخواص

اسم المؤلف: نورس حيدر مصطفى

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2005

الموضوع الدقيق: هندسة الكهرباء

الدرجة: ماجستير

الجامعة: جامعة بابل - كلية الهندسة - قسم الهندسة الكهربائية

مكان الجامعة: بابل