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 &ldquo / Conventional Pilots&rdquo / and &ldquo / Clustered Pilots&rdquo / 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&rsquo / s.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12608825/index.pdf |
| Date | 01 September 2003 |
| Creators | Etiler, Burkay |
| Contributors | Tuncer, Temel Engin |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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