Spatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique which realizes low complexity implementations in wireless communication systems. Due the transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter. Therefore, the complexity of the transmitter is lower compared to the complexity of traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter. Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At the receiver side, due to the SM transmission mechanism, detection is conducted using a low complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a single stream detector, SM achieves a multiplexing gain. A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation, the concept of SMis extended at the receiver side, using linear precoding with Channel State Information at the Transmitter (CSIT). Even though receive space modulation does not preserve the single RF chain configuration of SM, due to the deployed linear precoding, it can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual Multiple-Input Multiple-Output (VMIMO) architecture. Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of SM and its extension in different forms of MIMO communication. In particular, a realistic power model for the power consumption of a Base Station (BS) is deployed in order to assess the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that SM is significantly more energy efficient compared to the traditional MIMO techniques. In the considered system setup, it is shown that SM is up to 67% more energy efficient compared to the benchmark systems. In addition, the concept of space modulation is researched at the receiver side. Specifically, based on the union bound technique, a framework for the evaluation of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space modulation is developed. Because receive space modulation deploys linear precoding with CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided. It is concluded that receive space modulation is able to outperform the corresponding traditional MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order to form a novel virtual MIMO architecture. It is shown that the new architecture practically eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO space modulation architectures. This is undertaken by using precoding in a novel fashion. The evaluation of the new architecture is conducted using simulation and theoretical results.

Researchers have shown that by combining multiple input multiple output (MIMO) techniques with CDMA then higher gains in capacity, reliability and data transmission speed can be attained. But a major drawback of MIMO-CDMA systems is multiple access interference (MAI) which can reduce the capacity and increase the bit error rate (BER), so statistical analysis of MAI becomes a very important factor in the performance analysis of these systems. In this thesis, a detailed analysis of MAI is performed for binary phase-shift keying (BPSK) signals with random signature sequence in Raleigh fading environment and closed from expressions for the probability density function of MAI and MAI with noise are derived. Further, probability of error is derived for the maximum Likelihood receiver. These derivations are verified through simulations and are found to reinforce the theoretical results. Since the performance of MIMO suffers significantly from MAI and inter-symbol interference (ISI), equalization is needed to mitigate these effects. It is well known from the theory of constrained optimization that the learning speed of any adaptive filtering algorithm can be increased by adding a constraint to it, as in the case of the normalized least mean squared (NLMS) algorithm. Thus, in this work both linear and non-linear decision feedback (DFE) equalizers for MIMO systems with least mean square (LMS) based constrained stochastic gradient algorithm have been designed. More specifically, an LMS algorithm has been developed , which was equipped with the knowledge of number of users, spreading sequence (SS) length, additive noise variance as well as MAI with noise (new constraint) and is named MIMO-CDMA MAI with noise constrained (MNCLMS) algorithm. Convergence and tracking analysis of the proposed algorithm are carried out in the scenario of interference and noise limited systems, and simulation results are presented to compare the performance of MIMO-CDMA MNCLMS algorithm with other adaptive algorithms.

This dissertation introduces three novel multiuser detection approaches in Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems by blind signal separation (BSS) techniques. The conventional methodologies for multiuser detection have to retransmit channel state information (CSI) constantly from the transmitter in MIMO ODFM systems at the cost of economic efficiency, because they require more channel resources to improve the communication quality. Compared with the traditional methodologies, the proposed BSS methods are relatively efficient approaches without the unnecessary retransmission of channel state information. The current methodologies apply the space-time coding or the spatial multiplexing to implement an MIMO OFDM system, which requires relatively complex antenna design and allocation in the transmitter. The proposed Spatial Division Multiple Access (SDMA) method enables different mobile users to share the same bandwidth simultaneously in different geographical locations, and this scheme requires only one antenna for each mobile user. Therefore, it greatly simplifies the antenna design and allocation. The goal of this dissertation is to design and implement three blind multiuser detection schemes without knowing the channel state information or the channel transfer function in the SDMA-based uplink MIMO OFDM system. The proposed scenarios include: (a) the BSS-only scheme, (b) the BSS-Minimum Mean Square Error (MMSE) scheme, and (c) the BSS-Minimum Bit Error Ratio (MBER) scheme. The major contributions of the dissertation include: (a) the three proposed schemes save the commercially expensive cost of channel resources; (b) the proposed SDMA-based uplink MIMO OFDM system simplifies the requirements of antennas for mobile users; (c) the three proposed schemes obtain high parallel computing efficiency through paralleled subcarriers; (d) the proposed BSS-MBER scheme gains the best BER performance; (e) the proposed BSS-MMSE method yields the best computational efficiency; and (f) the proposed BSS-only scenario balances the BER performance and computational complexity.

The next-generation wireless technologies are currently being researched to address the ever-increasing demands for higher data rates, massive connectivity, improved reliability, and extended coverage. Recently, massive multiple-input multiple-output (MIMO) has gained significant attention as a new physical-layer transmission technology that can achieve unprecedented spectral and energy efficiency gains via aggressive spatial multiplexing. Thus, massive MIMO has been one of the key enabling technologies for the fifth-generation and subsequent wireless standards. This dissertation thus focuses on developing a system, channel, and signal models by considering the practical wireless transmission impairments for massive MIMO systems, and ascertaining the viability of massive MIMO in fulfilling massive access, improved spectrum, enhanced security, and energy efficiency requirements. Specifically, new system and channel models, pilot sequence designs and channel estimation techniques, secure transmit/receive beamforming techniques, transmit power allocation schemes with enhanced security provisions, energy efficiency, and user fairness, and comprehensive performance analysis frameworks are developed for massive MIMO-aided non-orthogonal multiple access (NOMA), cognitive spectrum-sharing, and wireless relaying architectures.Our first work focuses on developing physical-layer transmission schemes for NOMA-aided massive MIMO systems. A spatial signature-based user-clustering and pilot allocation scheme is first formulated, and thereby, a hybrid orthogonal multiple access (OMA)/NOMA transmission scheme is proposed to boost the number of simultaneous connections. In our second work, the viability of invoking downlink pilots to boost the achievable rate of NOMA-aided massive MIMO is investigated. The third research contribution investigates the performance of underlay spectrum-sharing massive MIMO systems for reverse time division duplexing based transmission strategies, in which primary and secondary systems concurrently operate in opposite directions. Thereby, we show that the secondary system can be operated with its maximum average transmit power independent of the primary system in the limit of infinity many primary/secondary base-station antennas. In our fourth work, signal processing techniques, power allocation, and relay selection schemes are designed and analyzed for massive MIMO relay networks to optimize the trade-off among the achievable user rates, coverage, and wireless resource usage. Finally, the cooperative jamming and artificial noise-based secure transmission strategies are developed for massive MIMO relay networks with imperfect legitimate user channel information and with no channel knowledge of the eavesdropper. The key design criterion of the aforementioned transmission strategies is to efficiently combine the spatial multiplexing gains and favorable propagation conditions of massive MIMO with properties of NOMA, underlay spectrum-sharing, and wireless relay networks via efficient signal processing.

Thanks to its improved capabilities, the Multiple Input Multiple Output (MIMO) radar is attracting the attention of researchers and practitioners alike. Because it transmits orthogonal or partially correlated waveforms, this emerging technology outperformed the phased array radar by providing better parametric identifiability, achieving higher spatial resolution, and designing complex beampatterns. To avoid jamming and enhance the signal to noise ratio, it is often interesting to maximize the transmitted power in a given region of interest and minimize it elsewhere. This problem is known as the transmit beampattern design and is usually tackled as a two-step process: a transmit covariance matrix is firstly designed by minimizing a convex optimization problem, which is then used to generate practical waveforms. In this work, we propose simple novel methods to generate correlated waveforms using finite alphabet constant and non-constant-envelope symbols. To generate finite alphabet waveforms, the proposed method maps easily generated Gaussian random variables onto the phase-shift-keying, pulse-amplitude, and quadrature-amplitude modulation schemes. For such mapping, the probability density function of Gaussian random variables is divided into M regions, where M is the number of alphabets in the corresponding modulation scheme. By exploiting the mapping function, the relationship between the cross-correlation of Gaussian and finite alphabet symbols is derived. The second part of this thesis covers the topic of target parameter estimation. To determine the reflection coefficient, spatial location, and Doppler shift of a target, maximum likelihood estimation yields the best performance. However, it requires a two dimensional search problem. Therefore, its computational complexity is prohibitively high. So, we proposed a reduced complexity and optimum performance algorithm which allows the two dimensional fast Fourier transform to jointly estimate the spatial location and Doppler shift. To assess the performance of the proposed estimators, the Cramér-Rao Lower Bound (CRLB) is derived. Simulation results show that the mean square estimation error of the proposed estimators achieve the CRLB. Keywords: Collocate antennas, multiple-input multiple-output (MIMO) radar, Finite alphabet waveforms, Hermite polynomials, Reflection coefficient, Doppler, Spatial location, Cramér-Rao Lower Bound.

With the advancement of wireless communication systems, the demand for higher data rates is increasing exponentially. Non Orthogonal Multiple Access (NOMA) is expected to play an important role in 5G new radio networks. In contrast to conventional multiple access schemes, NOMA allows different users to efficiently share the same resources (i.e., time, frequency and code) at different power levels so that the user with lower channel gain is served with a higher power and vice versa. Multiple Input Multiple Output (MIMO) technology to support multiple users, employ tens or even hundreds of antennas at the base station which increases throughput and spectrum efficiency. The combination of NOMA and MIMO techniques can achieve significant performance gains and provide better wireless services to cope with the demands of massive connectivity. In this thesis, we analyze the performance of NOMA-MIMO system. We derive analytical expressions for the performance metrics like Outage Probability (OP) and Symbol Error Rate (SER) in power domain of NOMA-MIMO communication system. The numerical results are validated with the simulation results in MATLAB and the influencing factors for better performance of the system are analysed.

Yes / This paper presented a planar printed multiple-input-multiple-output (MIMO) antenna with a dimension of 100 x 45 mm2. It composed of two crescent shaped radiators placed symmetrically with respect to the ground plane. Neutralization line applied to suppress mutual coupling. The proposed antenna examined both theoretically and experimentally, which achieves an impedance bandwidth of 18.67% (over 2.04-2.46 GHz) with a reflection coefficient < -10 dB and mutual coupling minimization of < -20 dB. An evaluation of MIMO antennas is presented, with analysis of correlation coefficient, total active reflection coefficient (TARC), capacity loss and channel capacity. These characteristics indicate that the proposed antenna suitable for some wireless applications.

<p> A multiple-input multiple-output (MIMO) communication system has the potential to provide reliable transmissions at high data rates. However, the computational cost of achieving this promising performance can be quite substantial. With an emphasis on practical implementations, the MIMO systems employing the low cost linear receivers are studied in this thesis. The optimum space-time block codes (STBC) that enable a linear receiver to achieve its best possible performance are proposed for various MIMO systems. These codes satisfy an intra and inter orthogonality property, and are called unitary trace-orthogonal codes. In addition, several novel transmission schemes are specially designed for linear receivers with the use of the proposed code structure. The applications of the unitary trace-orthogonal code are not restricted to systems employing linear receivers. The proposed code structure can be also applied to the systems employing other types of receivers where several originally intractable code design problems are successfully solved.</p> <p>The communication schemes presented in this thesis are outlined as follows: •For a MIMO system with N ≥ M, where M and N are the number of transmitter and receiver antennas, respectively, the optimal full rate linear STBC for linear receivers is proposed and named unitary trace-orthogonal code. The proposed code structure is proved to be necessary and sufficient to achieve the minimum detection error probability for the system. • When applied to a multiple input single output (MISO) communication system, a special linear unitary trace-orthogonal code, named the Toeplitz STBC, is proposed. The code enables a linear receiver to provide full diversity and to achieve the optimal tradeoff between the detection error and the data transmission rate. This is, thus far, the first code that possesses such properties for an arbitrary MISO system that employs a linear receiver. • In MIMO systems in which N ≥ M and the signals are transmitted at full symbol rate, the highest diversity gain achievable by linear receivers is analyzed and shown to be N - M + 1. To improve the performance of a linear receiver, a multi-block transmission scheme is proposed, in which signals are coded so that they span multiple independent channel realizations. An optimal full rate linear STBC for this system that minimizes the detection error probability is presented. The code is named multi-block unitary trace-orthogonal code. The resulting system has an improved diversity gain. Furthermore, by relaxing the code from the full symbol rate constraint, a special multi-block transmission scheme is proposed. This scheme achieves a much improved diversity gain than those with full symbol rate. • The unitary trace-orthogonal code can also be applied to a system that employs a maximum-likelihood (ML) receiver rather than the simple linear receiver. For such a system, a systematic design of full diversity unitary trace-orthogonal code is presented for an arbitrary data transmission rate. </p> <p>In summary, when a simple linear receiver is employed, unitary trace-orthogonal codes and their optimality properties are exploited for various multiple antenna communication systems. Some members from this code family can also enable an optimal performance of ML detection. </P> / Thesis / Doctor of Philosophy (PhD)

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