Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Turbo Equalization in Wireless Systems

In this thesis, in order to view the error performance of a digital communication system in which Low Density Parity Check Codes (LDPC) are used a channel encoder are used a channel encoder and Orthogonal Frequency Division Multiplexing (OFDM) system is explained. And error performance analysis has been made on different types of fading channels.

While designing a mobile radio and satellite communication system the most important points are reliable communication and transmitting the message with least lost. Since LPDC codes are very large Euclidean distance and use iterative decoding algorithms, they have high error correcting capacity and very close performances to Shannon limit.

OFDM signaling is proven to be an effective way to combat the negative effects of fading and multi path by dividing the frequency selective channel into a number of flat fading sub channels corresponding to the OFDM sub carriers’ frequencies. When compared to single carrier systems, channel equalization is less complex, and sensitivity to channel estimation. However, OFDM systems are more sensitive carrier frequency offsets than single carrier systems are. Further, desirable properties of OFDM are heavily conditioned upon the availability of accurate channel. There has been much research done on channel estimation.

Furthermore to reduce intersymbol interference is used equalizer. This equalizer use different estimation methods.

In this study, Low Density Parity Check codes and OFDM with estimation theory, the cannel and coda is estimated. The main goal is; estimative channel and code are annihilated the noise and multi paths along the channel.

Thus, transmitter, generate the code, provide that in the receiver decode it correctly and the code isn’t much distortion.

In this study, regular LDPC codes with minimum Least Square estimation and Maximum Likelihood estimation estimated the channel and the code.

KARA Sarper
Danışman : Prof. Dr. Aydın AKAN

Anabilim Dalı : Elektrik Elektronik Mühendisliği

Mezuniyet Yılı : 2008

Tez Savunma Jürisi : Prof. Dr. Aydın AKAN

Prof. Dr. Sıddık YARMAN

Prof. Dr. Hakan Ali ÇIRPAN

Prof. Dr.Ahmet SERTBAŞ

Prof. Dr. Osman Nuri UÇAN