Arrayed Multicarrier Systems: Di¤use Channel Estimation and Reception

OFDM and MC-CDMA are multicarrier modulation schemes that have been proposed for 4G systems due to their ability to achieve high spectral e¢ ciency by using minimally spaced orthogonal subcarriers and provide robustness against frequency selectivity in wireless channels, without increasing the transceiver complexity. Arrayed-MIMO systems, which employ antenna arrays at both ends of the wireless link, exploit the spatial domain to provide an extra layer of co-channel interference cancellation and new ways of handling unwanted channel e¤ects. The main objective of this thesis is to integrate multicarrier schemes with antennaarrays to design e¢ cient arrayed multicarrier systems for 4G wireless communications, with emphasis on the modelling of di¤used channel, estimation of channel parameters and robust reception based on estimated parameters. Initially, an Array-OFDM system is proposed that integrates OFDM and antenna array technology to harness the spatial signatures of received signals. This provides space diversity in multipath channels, making it possible to realise high transmission rates envisioned for the next generation wireless systems. A diversity reception algorithm is proposed for Post-FFT OFDM systems employing an antenna array at the receiver. It is shown that the proposed Array-OFDM receiver outperforms the Multiple-Element-OFDM receiver (that uses multiple independent antenna elements) under various frequency-selective fading models. Secondly, an Arrayed MC-CDMA system is developed that combines MCCDMA and antenna array technology by exploiting the spatial and temporal domain to achieve performance gains in wireless channels having spatio-temporal di¤usion of the multipath. A di¤used vector channel model for arrayed MCCDMA systems is proposed to combat the di¤use channel interference. Simulation studies show that the use of this di¤used channel modelling in arrayed MC-CDMA receivers yields better bit error rate (BER) and SNIRout performance than receivers that ignore the presence of spatial and/or temporal di¤usion. Finally, an arrayed-MIMO MC-CDMA system is designed to operate in a frequency selective spatially di¤used environment. However, in a departure from conventional MC-CDMA systems, cyclic pre…xes or guard intervals are not used for the MC-CDMA system employed here so that valuable bandwidth is not wasted on cyclic pre…xes or guard intervals. The spatially di¤used arrayed-MIMO wireless channel is …rst characterised in terms of spatial, temporal and spread parameters. A robust blind algorithm is then proposed to estimate the channel parameters, followed by reception based on these parameters. The feasibility of the proposed system is supported by numerical results. 2 List of Publications