Orthogonal frequency division multiplexing (OFDM) systems with cyclic prefix (CP) can be used to protect signal from the time-variant multipath channel induced distortions. However, the presence of CP could greatly decrease the effective data rate, thus many recent research works have been focused on the multiple-input multiple-output (MIMO) OFDM systems without CP (CP-free), equipped with the space-time block codes (ST-BC). The constraint of the conventional MIMO-OFDM (without using the ST-BC) system is that the number of receive-antenna has to be greater than the transmit-antenna. In this thesis, we first consider the ST-BC MIMO-OFDM system and show that the above-mentioned constraint can be removed, such that the condition become that the receive antenna should be greater than one, that is the basic requirement for MIMO system. It is particular useful and confirm to the recently specification, e.g., 3GPP LTE (Long Term Evolution) where the system deploy the 2¡Ñ2 or 4¡Ñ4 antennas systems. This thesis also considers the effects of peak-to-average power ratio (PAPR) in the transmitter and In-phase/ Quadrature-phase (IQ) imbalance in the receiver, and solves them by using the adaptive Volterra predistorter and blind adaptive filtering approach of the nonlinear parameters estimation and compensation, along with the power measurement, respectively. After the compensator of IQ imbalance in the receiver, an equalizer under the framework of generalized sidelobe canceller (GSC) is derived for interference suppression. To further reduce the complexity of receiver implementation, the partially adaptive (PA) scheme is applied by exploiting the structural information of the signal and interference signature matrices. As demonstrated from computer simulation results, the performance of the proposed CP-free ST-BC MIMO-OFDM receiver is very similar to that obtained by the conventional CP-based ST-BC MIMO-OFDM system under either the predistortion or compensation scenario.

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<p>In this thesis, a MISO wireless communication system having even transmitter antennas and a single receiver antenna is considered, where neither the transmitter nor the receiver knows channel state information. Particularly when the number of transmitter antennas is two, a novel concept called a uniquely factorable constellation pair (UFCP) is first proposed for the systematic design of a noncoherent full diversity collaborative unitary space-time block code by normalizing two Alamouti codes. It is proved that such a unitary UFCP code assures the unique identification of both channel coefficients and transmitted signals in a noise-free case as well as full diversity for the noncoherent maximum likelihood (ML) receiver in a noise case. To further improve error performance, an optimal unitary UFCP code is designed by appropriately and uniquely factorizing a pair of energy-efficient cross quadrature amplitude modulation (QAM) constellations to maximize the coding gain subject to a transmission bit rate constraint. After a deep investigation of the fractional coding gain function, a technical approach developed in this thesis to maximizing the coding gain is to carefully design an energy scale to compress the first three largest energy points in the corner of the QAM constellations in the denominator of the objective as well as carefully design a constellation triple forming two UFCPs, with one collaborating with the other two so as to make the accumulated minimum Euclidean distance along the two transmitter antennas in the numerator of the objective as large as possible and at the same time, to avoid as many corner points of the QAM constellations with the largest energy as possible to achieve the minimum of the numerator. In other words, the optimal coding gain is attained by intelligent constellations collaboration and efficient energy compression. Another contribution of this thesis is to generalize the design for the two transmitter antennas into that of the noncoherent system with any even number of transmitter antennas. Using the Alamouti coding scheme and the Toeplitz matrix structure, a novel noncoherent nonunitary space-time block code, which is called an Alamoutibased Toeplitz space-time block code, is proposed. By the fundamentals of Galois theory and algebraic number theory, two important properties on the two Alamouti codes generated from a pair of coprime phase shift keying (PSK) constellations, i.e., the uniqueness of factorization itself and the shift-invariant uniqueness of factorization, are first revealed and rigorously proved. Then, it is further shown that it is these two kinds of the unique factorizations that enable the unique blind identification of both the channel coefficients and the transmitted signals by only processing two block received signals as well as noncoherent full diversity with a generalized likelihood ratio test (GLRT) receiver. In addition, a full diversity unitary code design is also proposed by simply applying the QR decomposition to the full diversity nonunitary Alamoutibased Toeplitz space-time block code. Computer simulations demonstrate that error performance of both optimal unitary UFCP code and Alamouti-based Toeplitz code presented in this thesis outperform those of the differential code and the SNR-efficient training code, which is the best code in current literatures for the system.</p> / Master of Applied Science (MASc)

Over recent years, the research and studies have focused on innovative solutions in various aspects and phases related to the high demands on data rate and energy for fifth-generation and beyond (B5G). This thesis aims to improve the energy efficiency, error rates, low-resolution ADCs/DACs, antenna array structures and sum-rate performances of a single cell downlink broadband millimetre-wave (mmWave) systems with orthogonal frequency division multiplexing (OFDM) modulation and deploying multi-user massive multiple inputs multiple outputs (MU mMIMO) by applying robust beamforming techniques and detection algorithms that support multiple streams per user (UE) in various environments and scenarios to achieve low complexity system design with reliable performance and significant improvement in users perceived quality of service (QoS). The performance of the four 5G candidate mmWave frequencies, 28 GHz, 39 GHz, 60 GHz, and 73 GHz, are investigated for indoor/outdoor propagation scenarios, including path loss models and multipath delay spread values. Results are compared to confirm that the received power and delay spread is decreased with increasing frequency. The results were also validated with the measurement findings for 60 GHz. Then several proposed design models of beamforming are studied and implemented modified algorithms of Hybrid Beamforming (HBF) approaches in indoor/outdoor scenarios over large scale fading wideband mmWave /Raleigh channels. Firstly, three beamforming based diagonalize the Equivalent Virtual Channel Matrix (EVCM) schemes with the optimal linear combining methods are presented to overcoming the self-interference problems in Quasi-Orthogonal-Space Time Block Code (QO-STBC) systems over narrowband mmWave Single-User mMIMO (SU mMIMO). The evaluated results show that the proposed beamforming based- Single Value Decomposition (SVD) outperforms the conventional beamforming and standard QO-STBC techniques in terms of BER and spectrum efficiency. Next, the proposed HBF algorithm approaches with the fully/ partially connected structures are developed and applied for sum-rate and symbol error rate (SER) performance maximization MU mMIMO-OFDM system, including HBF based on block diagonalization (BD) method Constraint/Unconstraint RF Power, Codebook, Kalman schemes. In addition, the modified near optimal linear HBF-Zero Forcing (HBF-ZF) and HBF-Minimum Mean Square Error (HBF MMSE) schemes, considering both fully-connected and partially-connected structures. Finally, Simulation results using MATLAB platform, demonstrate that the proposed HBF based codebook and most likely HBF based-unconstraint RF power algorithms achieve significant performance gains in terms SER and sum-rate efficiency as well as show high immunity against the deformities and disturbances in the system compared with other HBF algorithm schemes. / Ministry of Higher Education and Scientific Research, the Republic of Iraq