Performance enhancement for filter bank multicarrier methods in multi-antenna wireless communication systems

This thesis investigates filter bank based multicarrier modulation using offset quadrature amplitude modulation (FBMC/OQAM), which is characterised by a critically sampled FBMC system that achieves full spectral efficiency in the sense of being free of redundancy. As a starting point, a performance comparison between FBMC/OQAM and oversampled (OS) FBMC systems is made in terms of per-subband fractionally spaced equalisation in order to compensate for the transmission distortions caused by dispersive channels. Simulation results show the reduced performance in equalising FBMC/OQAM compared to OS-FBMC, where the advantage for the latter stems from the use of guard bands. Alternatively, the inferior performance of FBMC/OQAM can be assigned to the inability of a per-subband equaliser to address the problem of potential intercarrier interference (ICI) in this system. The FBMC/OQAM system is analysed by representing the equivalent transmultiplexed channel including the filter banks as a polynomial matrix. The formulated polynomial matrix is demonstrated as a tri-diagonal matrix plus two corner elements which indicates that the induced ICI is limited to the direct adjacent spectrally overlapped subchannels. Based on polynomial matrix algebra, an equaliser is proposed which considers the cross terms between subchannels rather iii Abstract than performing a per-subband equalisation. The proposed equaliser is obtained through the inversion of the channel polynomial matrix; due to its reduced-rank nature, this inversion requires the extension of pseudo-inversion principles to the domain of polynomial matrices, and the inclusion of a regularisation term for enhanced stability and system performance. Some numerical examples demonstrate the ability of the proposed equaliser to suppress both ISI and ICI. Furthermore, this thesis combines FBMC/OQAM with multi-antenna architectures. In this scenario, the FBMC/OQAM system will not only suffer from ISI and ICI but also from spatial or inter-antenna interference (IAI). The multipleinput multiple-output (MIMO) channel including the filter bank system is formulated as a polynomial matrix. A polynomial matrix pseudo-inverse of the equivalent channel polynomial matrix is proposed to approximately eliminate ISI, ICI, and IAI. Examples and simulation results are presented to underpin the performance of the proposed architecture.than performing a per-subband equalisation. The proposed equaliser is obtained through the inversion of the channel polynomial matrix; due to its reduced-rank nature, this inversion requires the extension of pseudo-inversion principles to the domain of polynomial matrices, and the inclusion of a regularisation term for enhanced stability and system performance. Some numerical examples demonstrate the ability of the proposed equaliser to suppress both ISI and ICI. Furthermore, this thesis combines FBMC/OQAM with multi-antenna architectures. In this scenario, the FBMC/OQAM system will not only suffer from ISI and ICI but also from spatial or inter-antenna interference (IAI). The multipleinput multiple-output (MIMO) channel including the filter bank system is formulated as a polynomial matrix. A polynomial matrix pseudo-inverse of the equivalent channel polynomial matrix is proposed to approximately eliminate ISI, ICI, and IAI. Examples and simulation results are presented to underpin the performance of the proposed architecture.