Comparison of the intercarrier interference cancellation methods in OFDM systems

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2007

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Etiler, Burkay

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In OFDM systems carrier frequency offset is observed due to Doppler shift and transmitter-receiver frequency mismatches. This offset induces ICI (Intercarrier Interference). In this thesis, repeated data methods and pilot-aided carrier frequency offset(CFO) estimation methods and windowing techniques are used to mitigate the frequency offset problem and a performance comparison is made between these ICI cancellation techniques. Repeated data methods use only half of the bandwidth for information transmission to eliminate the ICI at the receiver. We have implemented repeated data methods including Self cancellation scheme and Symmetric Symbol Repetition (SSR) schemes to overcome ICI problem. We have also implemented Adjacent Conjugate Symbol Repetiton (ACSR) and Symmetric Conjugate Symbol Repetiton (SCSR) methods to mitigate both phase rotations and ICI. CFO estimation and correction methods generally use pilot sequences. We implemented the “Conventional Pilots” and “Clustered Pilots” pilot-aided CFO estimation techniques for ICI cancellation. Furthermore, we also implemented a new scheme by using the odd symmetry between pilot symbols. Nyquist windowing techniques apply windowing at the receiver side. We have implemented second order polynomial class of Nyquist windows and Nyquist window with Franks pulse used to mitigate ICI. These ICI cancellation methods are compared in AWGN and multipath Rayleigh fading channel models in terms of BER and carrier to interference ratio. It is shown that repeated data methods shows better performances than pilot-aided CFO estimation methods with a cost of increased bandwidth usage especially in high SNR’s.

Subject Keywords

Telecommunication (including telegraphy, telephone, radio, radar, television)

URI

http://etd.lib.metu.edu.tr/upload/2/12608825/index.pdf
https://hdl.handle.net/11511/16965

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

B. Etiler, “Comparison of the intercarrier interference cancellation methods in OFDM systems,” M.S. - Master of Science, Middle East Technical University, 2007.