Time variations of a doubly selective channel and insufficient cyclic prefix (CP) length in an Orthogonal Frequency Division Multiplexing (OFDM) transmission system, cause intercarrier interference (ICI) and interblock interference (IBI) as significant limitations. In the first part of this thesis, we investigate the problem of joint ICI and IBI mitigation in multiple-input multiple-output OFDM (MIMO-OFDM) systems. We assume that the channel delay spread is larger than the CP, and also the channel varies within each OFDM block. The doubly selective channel is modeled using basis expansion model (BEM) and four time-domain equalizers are developed. Also, a frequency-domain equalization approach is proposed to confront ICI/IBI. Practical implementation of MIMO-OFDM systems also suffers from the effect of In-phase/ Quadrature-phase (IQ) imbalance in the analog front-end section. This phenomenon can severely degrade the achievable performance. In the second part of this thesis, we study the digital compensation of both the transmitter and receiver IQ imbalances in MIMO-OFDM transmission over doubly selective channels. In particular, we employ the BEM to develop a novel IQ formulation for a time-varying channel. Using this formulation, we suggest a general scheme to jointly mitigate the IQ imbalance and channel time variation effects. An important feature of the proposed equalizers is that no bandwidth expansion or redundancy insertion is required except for the CP. Finally, we provide simulation results over two justify; TEXT-INDENT: 18pt; MARGIN: 0cm 0cm 0pt; unicode-bidi: embed; DIRECTION: ltr" Keywords OFDM, MIMO, intercarrier interference, interblock interference, IQ imbalance, equalization
