Transmission methods for wireless multi carrier systems in time-varying environments
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Fast time-variant and frequency selective radio channels lead to significant challenges for the design of wireless data transmission systems. A scenario where such difficult channels occur is the data link to a high speed train.
In this work, we present some transmission methods that are particularly suited for fast time variant and frequency selective channels. As a basis, we use a combination of orthogonal frequency division multiplexing (OFDM) and M-ary frequency shift keying (MFSK). By using OFDM, it is possible to avoid inter symbol interference so that there is no need for a complex equalizer even for high data rates. Due to the fact that MFSK can be detected noncoherently, OFDM-MFSK-based modulation schemes do not rely on exact channel estimation which leads to very robust transmission methods.
After introducing several OFDM-MFSK-based modulation schemes, we present methods that can improve the detection by using iterative receivers and multiple symbol detection. We also show how the performance can be improved by a proper matching of the bit mapping and the channel code. Furthermore, we show that the introduced modulation schemes can be regarded as subspace-based information transmission.
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Fakultät für Ingenieurwissenschaften und Informatik
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DFG Project uulm
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FSK, Inkohärente Detektion, Zeitvariante Funkkanäle, Frequenzumtastung, Iterative Decodierung, Mehrträgerverfahren, OFDM, Orthogonal frequency division multiplexing, DDC 620 / Engineering & allied operations