5825

5440

كارشناسي ارشد

مخابرات

اصفهان: دانشگاه صنعتي اصفهان، دانشكده برق و كامپيوتر

1389

هشت،78ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

علي محمد دوست حسيني

محمد جواد اميدي

5/2/90

مهندسي برق و كامپيوتر

ID5440

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

3 ICI Mitigation Due to Doppler Phenomenon in Doubly Selective Channels with Joint Kalman Filter and Recursive Equalizer Neda Mohammadizadeh n mohammadizadeh@ec iut ac ir Date of Submission August 2010 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisor Dr Ali Mohamad Doost Hoseini alimdh@cc iut ac ir Abstract Over the last decades wireless communications has emerged and played an important role in the daily activities of human beings This is due to the fact that wireless connectivity is making exciting inroad to everywhere without fixed transmitter receiver or any physical connection cable In a wireless channel the signal from a transmitter interferes with its own copies due to different channel paths leading to Inter Symbol Interference ISI So multipath propagation usually introduces new problems in symbol detection OFDM as a multichannel modulation has the ability to overcome this phenomena by dividing the high rate data stream into N lower rate substreams The substreams are transmitted simultaneously over orthogonal long duration subcarriers causing much less severe ISI because each subcarrier s bandwidth is much less than the channel coherence bandwidth However OFDM is very vulnerable to channel time variations especially within one OFDM symbol In such cases the orthogonality between subcarriers breaks down easily resulting into Inter Carrier Interference ICI This phenomenon may degrade the performance considerably On the other hand when transmitting high rate data at a high frequency band OFDM systems would experience time and frequency selective or doubly selective phenomena in which the duration of an OFDM block is comparable to the coherence time as well as multipath spread of the channel Time varying impairments is modeled by Doppler shift In order to overcome this problem a number of conventional schemes have been proposed to suppress or subtract out the ICI Examples are equalization ICI self cancellation coding Equalization is chosen in many practical cases due to high performance reliability and implementation only in the receiver It substantially relies on matrix inversion and for fast varying channels and large number of subcarriers requires high computations To reduce the complexity applying an iterative ICI equalization one can exploit channel matrix properties to separate ICI free and pure ICI components in frequency domain and compensate ICI iteratively rather than through exact matrix inversion

علي محمد دوست حسيني

محمد جواد اميدي