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Yayın Design and performance analysis of a novel trellis coded space-time-frequency transmission scheme(Işık Üniversitesi, 2004-07) Oğuz, Onur; Panayırcı, Erdal; Aygölü, Hasan Ümit; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Elektronik Mühendisliği Yüksek Lisans ProgramıThis work is concerned with a transmitter diversity technique for wireless communications over frequency selective fading channels. The proposed technique utilizes orthogonal frequency division multiplexing (OFDM) to transform a frequency selective fading channel into multiple flat fading sub channels on which space-frequency processing is applied and then additional space-time coding is applied in order to increase the diversity. In order to improve the performance of the system, a convenient trellis coding scheme is investigated and design criteria are established. Performance of proposed space-time-frequency OFDM (STF-OFDM) transmitter diversity technique has been examined by computer simulations.Yayın Design of reed-solomon and convolutional coded OFDM system and performance analysis(Işık Üniversitesi, 2003) Bal, Ufuk; Panayırcı, Erdal; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Elektronik Mühendisliği Yüksek Lisans ProgramıIn this study, OFDM and error-correcting codes, which have an important place in digital communication systems, have been studied. Literature research has been made on OFDM and error-correcting codes like Reed-Solomon and convolutional codes. Reed-Solomon and convolutional coded OFDM system has been designed. Furthermore, system's performance analysis has been made. OFDM is special case of multicarrier transmission. The basic principle of OFDM is to split a high-rate datastream into a number of lower rate streams that are transmitted similtuanesly over a number of subcarriers. One of the main reason to use OFDM is to increase the robustness against frequency selective fading or narrowband interference. In a single carrier system, a single fade or interferer can cause the entire link to fail, but in a multicarrier system, only a small percentage of the subcarriers will be affected. Error correcting codes can then be used to correct the errors. In error correcting, combining convolutional and block codes in a concatenated code is particularly powerful technique. In this study Reed-Solomon codes are used as an outer code and convolutional codes are used as an inner code.
