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A new differential transceiver with frequency-shift orthogonal keying (FSOK) technique is proposed for the multi- carrier spread spectrum (MC-SS) system over the fast changing frequency selective fading channels. The design of the transceiver involves the following procedures. First, the data stream is mapped into QPSK-FSOK symbols and spreaded by the frequency-shift orthogonal sequences. Second, the differential block encoder is exploited to combat the fast fading channels. The Chu sequence is adapted for the initial differential encoding, which conducts the post-FFT transmitted signal involving the low peak-to-average power ratio (PAPR) property. Next, at receiver, the maximum ratio combining (MRC) technique is used for the block-based differential frequency-domain equalizer, which can overcome fading channel effect without requiring channel estimation. Finally, an efficient maximum likelihood (ML) despreading and demapping scheme is used to detect the modulation symbols. Simulation result shows that, under mobile multipath fading environment, the proposed transceiver of MRC differential decoder can outperform the theoretical QPSK system and the conventional MC-SS system.
Date of Conference: 26-29 April 2009