published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Recent survey campaigns have shown a tremendous under utilization of the bandwidth allocated to various wireless services. Motivated by this and the ever increasing demand for wireless applications, the concept of cognitive radio (CR) systems has rendered hope to end the so called spectrum scarcity. This thesis presents various different facets related to the design and analysis of CR systems in a unified way. We begin the thesis by presenting an information theoretic study of cognitive systems working in the so called low interference regime of the overlay mode. We show that as long as the coverage area of a CR is less than that of a primary user (PU) device, the probability of the cognitive terminal inflicting small interference at the PU is overwhelmingly high. We have also analyzed the effect of a key parameter governing the amount of power allocated to relaying the PU message in the overlay mode of operation in realistic environments by presenting a simple and accurate approximation. Then, we explore the possibilities of statistical modeling of the cumulative interference due to multiple interfering CRs. We show that although it is possible to obtain a closed form expression for such an interference due a single CR, the problem is particularly difficult when it comes to the total CR interference in lognormally faded environments. In particular, we have demonstrated that fitting a two or three parameter lognormal is not a feasible option for all scenarios. We also explore the second-order characteristics of the cumulative interference by evaluating its level crossing rate (LCR) and average exceedance duration (AED) in Rayleigh and Rician channel conditions. We show that the LCRs in both these cases can be evaluated by modeling the interference process with gamma and noncentral χ2 processes, respectively. By exploiting radio environment map (REM) information, we have presented two CR scheduling schemes and compared their performance with the naive primary exclusion zone (PEZ) technique. The results demonstrate the significance of using an intelligent allocation method to reap the benefits of the tremendous information available to exploit in the REM based methods. At this juncture, we divert our attention to multiple-input multiple-output (MIMO) CR systems operating in the underlay mode. Using an antenna selection philosophy, we solve a convex optimization problem accomplishing the task and show via analysis and simulations that antenna selection can be a viable option for CRs operating in relatively sparse PU environments. Finally, we study the impact of imperfect channel state information (CSI) on the downlink of an underlay multiple antenna CR network designed to achieve signal-to-interference-plus-noise ratio (SINR) fairness among the CR terminals. By employing a newly developed convex iteration technique, we solve the relevant optimization problem exactly without performing any relaxation on the variables involved.

This thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel estimation process was 1.83 % and 6.1810 %, respectively for simulated and experimental data. Using experimental data, the RMSE before MIMO deconvolution process was 141.3 % and dropped down to 60.224 % and to 4.4545 %, respectively after LE and ICLE. At raw reception, the RMSE was 101.83 % and dropped down to 9.36 % and to 1.86 % using respectively LE and ICLE with simulated data. / by Gaultier Real. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

L'Internet des objets est l'un des concepts clefs stimulant l'évolution des réseaux mobiles dans le but de leur donner de nouvelles fonctionnalités de communication et de gestion d'objets dits connectés. Comparativement aux terminaux mobiles standards, les usages associés à ces objets connectés sont en général caractérisés par des débits modestes et de faibles ressources en capacité de calcul et en énergie. Les techniques de modulation spatiale (SM) sont proposées comme une solution prometteuse pour assurer les débits des objets connectés tout en maîtrisant le critère de la consommation énergétique. L'objectif de cette thèse est d'étudier les performances de différents schémas de transmission basés sur le concept SM mis en oeuvre en transmission ou en réception. Nous avons notamment proposé un système global de communication en liaisons montante (SM en transmission) et descendante (SM en réception) entre une station de base et un objet, dans lequel l'essentiel de la complexité de calcul est concentré à la station de base. Par ce système, une liaison avec un objet peut être établie en limitant les traitements au sein de l'objet à di simples fonctions d'activation/désactivation d'antenne et de détection à seuil. Par ailleurs, nous avons proposé des schémas SM étendus grâce auxquels l'efficacité spectrale atteignable devient égale au nombre d'antennes au sein de l'objet. Les expressions analytiques de la probabilité d'erreur binaire ont été développées pour l'ensemble des systèmes étudiés en utilisant différentes méthodes de détection. L'impact de la connaissance imparfaite de l'état des canaux de propagation ainsi que l'effet des corrélations entre antennes ont également été incorporés dans l'étude des performances des schémas SM de réception. Dans une dernière partie, nous avons proposé d'adapter les schémas SM de réception dans un environnement de propagation en ondes millimétriques en utilisant une formation de faisceau hybride analogique/numérique au niveau de l'émetteur. / Internet of Things is one of the keyword that represents the evolution in 5G that is able to connect the so-called Connected Devices (CD) to the network. These CDs are expected to require modest data rates and will be characterized by low resources in terms of both computation and energy consumption compared to other mobile multi-media devices. Spatial Modulation (SM) is proposed to be a promising solution to boost the data rate of the CD with a small ( or no) increase in energy consumption. Inspired by the advantages of SM, the objective of this thesis is to study the performance of different transmission scheme based on the SM concept at the transmitter and at tht receiver, for respectively an uplink and a downlink transmission between a BS and a CD. We proposed a global system where the higher computational complexity remains at the BS: The transmit SM is used for uplink, and the receive SM for downlink. It is shown that with SM, an ON­OFF keying for uplink and Single Tap detector for downlink could be sufficient for the transmission a the CD. Also, with Extended SM schemes, we increased the spectral efficiency of SM to be equal t< the number of antennas of CD in both uplink and downlink transmission. A framework for the derivation of the Bit Error Probability (BEP) is developed for all schemes with different detection methods. Impact of imperfect CSIT transmission has been studied when linear precoding is implemented for the receive spatial modulation, as well as the effect of antenna correlations. Finally we proposed to adapte the spatial modulation at the receiver with the mmWave environment, using hybrid beamformina at the transmitter.

A multiple-input-multiple-output, or MIMO, receiver receives multiple data streams in the same frequency band at the same time, significantly improving spectral efficiency. It has to preserve all the antenna aperture information and use it to deliver as many data streams as the antenna count. As the number of antennas increases, implementing a MIMO receiver system in the analog domain becomes difficult. A digital MIMO receiver architecture that digitizes all the antenna inputs on the element level offers multiple advantages. Digital MIMO signal processing is flexing and powerful. Complex space-time array processing is supported and so is digital array calibration. Therefore, the digital MIMO receiver architecture has become the most promising architecture for future massive MIMO systems. However, the digital MIMO receiver architecture has a disadvantage, namely that the spatial selectivity feature is missing in the RF/analog domain. At the target frequency band, multiple spatial signals can arrive at the antenna array at different power levels. Conventional spectral filtering is ineffective at in-band frequency so all the spatial signals have to co-exist in all the receiver elements and the following analog-to-digital converters (A/Ds). The instantaneous dynamic range required for these RF/analog and mixed-signal circuits will be limited by the strongest spatial signal on the upper bound, and the weakest spatial signal on the lower bound. A high instantaneous dynamic range requirement directly translates to high power consumption and high cost. Therefore, the recovery of spatial selectivity in the RF/analog domain is necessary. The first thrust toward recovering RF/analog spatial selectivity in a digital MIMO receiver is the scalable spatial notch suppression technique. Knowing the direction of a strong spatial blocker, a spatial notch, instead of beams, can be synthesized to the blocker direction to filter it out. This means that all the analog baseband outputs will show high conversion gains to signals from all directions but one, namely the blocker direction. In this way, high sensitivity is preserved in most directions to receiver multiple weak spatial signals simultaneously, which will be digitized, and separated in the digital domain. In the blocker direction, a low conversion gain filters the blocker out, preventing it from demanding high dynamic range for all of the RF/analog circuits and the A/Ds. In order to synthesize the scalable spatial notch, a spatial notch filter (SNF) is designed to provide lower input impedance in the blocker direction and high impedance in other directions. Using this spatially modulated impedance to load a current mode receiver leads to spatially modulated conversion gain. A transparent RF front-end translates this impedance to the antenna interface to achieve spatial notch suppression right at the antennas. A feedforward spatial notch canceler (FF SNC) uses the available isolated blocker information to improve spatial suppression ratio. The spatial notch suppression is scalable through a baseband node, allowing the tiling of multiple ICs on the same PCB for larger scale MIMO systems. A prototype receiver array was implemented with a 65nm CMOS process. Experimental results showed 32dB steerable spatial notch suppression, more than 19db of suppression inside the notch direction across all frequencies. In-band output-referred IP3 was improved from -10dBV to +24dBV, from outside to inside the notch direction, and IIP3 was also improved from +11dBm to +18dBm. Single-element equivalent double-sideband noise figure (NFDSB,eq) was 2.2 to 4.6dB across the 0.1 to 1.7GHz operating frequency range, also showing an improvement compared to other multi-antenna receivers at similar frequency ranges. A second thrust is an RF/analog arbitrary spatial filtering receiver. Instead of filtering out strong spatial blockers, a more general and robust way to recover spatial selectivity is to impose an arbitrary spatial response that adaptively equalizes the power levels of all the spatial signals. In this way, all the spatial signals should have the same power level when reaching the A/Ds, allowing the use of low-power A/Ds with low dynamic ranges, which are essential for the realization of the digital massive MIMO solution. Such an arbitrary spatial filtering response requires the ability to synthesize multiple spatial notches that can be independently steered, the depth of the notches free adjusted. In addition, a few performance metrics need to be improved based on the first work. Spatial suppression ratio was limited by the lack of magnitude control in the first work. In-band in-notch linearity performance was limited by the use of voltage mode gyrators that requires a band-limiting high-impedance node, which also limits spatial suppression bandwidth. Also, the antenna array dimensions scale inversely with operating frequency. So pushing the receiver array to work at higher frequency is also desired. Toward these goals, a 65nm CMOS prototype receiver array was implemented. Wideband current-mode receiver front-ends that consist of inverter-based LNTAs and passive mixers can work up to 3.1GHz. A baseband current-mode beamformer can synthesize virtual grounds at the output nodes in the target notch directions, providing not only an arbitrary spatial response but also an baseband input impedance that is also spatially modulated, allowing spatial filtering at the LNTA output nodes. Current mode operation avoids the use of band-limiting high impedance nodes for strong spatial signals, leading to superior linearity and wideband spatial suppression. This 4-element prototype measured more than 50dB of spatial suppression ratios with single-notch settings across all measured directions. Up to three notches can be synthesized, each of which can be independently steered and its depth freely adjusted. An in-band OIP3 of +34dBV was measured, 10dB higher than the first work, due to the current mode operation. A 20dB suppression bandwidth of 320MHz, or equivalently 64% was measured, more than 20× improvement than the first work, also due to the current mode operation. On a separate note, an ultra-wideband LNTA was also designed for an RF channelizing receiver work. This two-stage LNTA makes use of a gm-boosted current mirror structure to harness the linearity advantage of a current mirror, the low-noise input matching of the feedback structure, the high transconductance gain of a two-stage structure and an ultra-wideband input matching advantage of a gyrator. The implemented 65nm CMOS prototype is fully integrated, and provides 242mS peak transconductance gain over 0.6-9.6GHz operating frequency range. It achieves 4.5dB of NF and +6.5dBm of IIP3. In summary, RF/analog spatial selectivity can be recovered in innovative methods to relax the dynamic range requirement for all the RF/analog circuits together with the following A/Ds in a digital MIMO receiver. The scalable spatial notch suppression technique and the arbitrary spatial filtering technique allow the use of low-power A/Ds, which are essential for truly massive MIMO systems with manageable power consumption.

由於在盲語音分離的應用，線性準平穩源訊號混合的盲識別獲得了巨大的研究興趣。在這個問題上，我們利用準穩態源訊號的時變特性來識別未知的混合系統系數。傳統的方法有二：i)基於張量分解的平行因子分析(PARAFAC);ii)基於對多個矩陣的聯合對角化的聯合對角化算法(JD)。一般來說，PARAFAC和JD 都採用了源聯合的提取方法；即是說，對應所有訊號源的系統係數在升法上是用時進行識別的。 / 在這篇論文中，我利用Khati-Rao(KR)子空間來設計一種新的盲識別算法。在我設計的算法中提出一種與傳統的方法不同的提法。在我設計的算法中，盲識別問題被分解成數個結構上相對簡單的子問題，分別對應不同的源。在超定混合模型，我們提出了一個專門的交替投影算法(AP)。由此產生的算法，不但能從經驗發現是非常有競爭力的，而且更有理論上的利落收斂保證。另外，作為一個有趣的延伸，該算法可循一個簡單的方式應用於欠混合模型。對於欠定混合模型，我們提出啟發式的秩最小化算法從而提高算法的速度。 / Blind identification of linear instantaneous mixtures of quasi-stationary sources (BI-QSS) has received great research interest over the past few decades, motivated by its application in blind speech separation. In this problem, we identify the unknown mixing system coefcients by exploiting the time-varying characteristics of quasi-stationary sources. Traditional BI-QSS methods fall into two main categories: i) Parallel Factor Analysis (PARAFAC), which is based on tensor decomposition; ii) Joint Diagonalization (JD), which is based on approximate joint diagonalization of multiple matrices. In both PARAFAC and JD, the joint-source formulation is used in general; i.e., the algorithms are designed to identify the whole mixing system simultaneously. / In this thesis, I devise a novel blind identification framework using a Khatri-Rao (KR) subspace formulation. The proposed formulation is different from the traditional formulations in that it decomposes the blind identication problem into a number of per-source, structurally less complex subproblems. For the over determined mixing models, a specialized alternating projections algorithm is proposed for the KR subspace for¬mulation. The resulting algorithm is not only empirically found to be very competitive, but also has a theoretically neat convergence guarantee. Even better, the proposed algorithm can be applied to the underdetermined mixing models in a straightforward manner. Rank minimization heuristics are proposed to speed up the algorithm for the underdetermined mixing model. The advantages on employing the rank minimization heuristics are demonstrated by simulations. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Lee, Ka Kit. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 72-76). / Abstracts also in Chinese. / Abstract --- p.i / Acknowledgement --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Settings of Quasi-Stationary Signals based Blind Identification --- p.4 / Chapter 2.1 --- Signal Model --- p.4 / Chapter 2.2 --- Assumptions --- p.5 / Chapter 2.3 --- Local Covariance Model --- p.7 / Chapter 2.4 --- Noise Covariance Removal --- p.8 / Chapter 2.5 --- Prewhitening --- p.9 / Chapter 2.6 --- Summary --- p.10 / Chapter 3 --- Review on Some Existing BI-QSS Algorithms --- p.11 / Chapter 3.1 --- Joint Diagonalization --- p.11 / Chapter 3.1.1 --- Fast Frobenius Diagonalization [4] --- p.12 / Chapter 3.1.2 --- Pham’s JD [5, 6] --- p.14 / Chapter 3.2 --- Parallel Factor Analysis --- p.16 / Chapter 3.2.1 --- Tensor Decomposition [37] --- p.17 / Chapter 3.2.2 --- Alternating-Columns Diagonal-Centers [12] --- p.21 / Chapter 3.2.3 --- Trilinear Alternating Least-Squares [10, 11] --- p.23 / Chapter 3.3 --- Summary --- p.25 / Chapter 4 --- Proposed Algorithms --- p.26 / Chapter 4.1 --- KR Subspace Criterion --- p.27 / Chapter 4.2 --- Blind Identification using Alternating Projections --- p.29 / Chapter 4.2.1 --- All-Columns Identification --- p.31 / Chapter 4.3 --- Overdetermined Mixing Models (N > K): Prewhitened Alternating Projection Algorithm (PAPA) --- p.32 / Chapter 4.4 --- Underdetermined Mixing Models (N <K) --- p.34 / Chapter 4.4.1 --- Rank Minimization Heuristic --- p.34 / Chapter 4.4.2 --- Alternating Projections Algorithm with Huber Function Regularization --- p.37 / Chapter 4.5 --- Robust KR Subspace Extraction --- p.40 / Chapter 4.6 --- Summary --- p.44 / Chapter 5 --- Simulation Results --- p.47 / Chapter 5.1 --- General Settings --- p.47 / Chapter 5.2 --- Overdetermined Mixing Models --- p.49 / Chapter 5.2.1 --- Simulation 1 - Performance w.r.t. SNR --- p.49 / Chapter 5.2.2 --- Simulation 2 - Performance w.r.t. the Number of Available Frames M --- p.49 / Chapter 5.2.3 --- Simulation 3 - Performance w.r.t. the Number of Sources K --- p.50 / Chapter 5.3 --- Underdetermined Mixing Models --- p.52 / Chapter 5.3.1 --- Simulation 1 - Success Rate of KR Huber --- p.53 / Chapter 5.3.2 --- Simulation 2 - Performance w.r.t. SNR --- p.54 / Chapter 5.3.3 --- Simulation 3 - Performance w.r.t. M --- p.54 / Chapter 5.3.4 --- Simulation 4 - Performance w.r.t. N --- p.56 / Chapter 5.4 --- Summary --- p.56 / Chapter 6 --- Conclusion and Future Works --- p.58 / Chapter A --- Convolutive Mixing Model --- p.60 / Chapter B --- Proofs --- p.63 / Chapter B.1 --- Proof of Theorem 4.1 --- p.63 / Chapter B.2 --- Proof of Theorem 4.2 --- p.65 / Chapter B.3 --- Proof of Observation 4.1 --- p.65 / Chapter B.4 --- Proof of Proposition 4.1 --- p.66 / Chapter C --- Singular Value Thresholding --- p.67 / Chapter D --- Categories of Speech Sounds and Their Impact on SOSs-based BI-QSS Algorithms --- p.69 / Chapter D.1 --- Vowels --- p.69 / Chapter D.2 --- Consonants --- p.69 / Chapter D.1 --- Silent Pauses --- p.70 / Bibliography --- p.72

Different from multiple-input multiple-output (MIMO) systems, a major challenge for cooperative communications is the problem of synchronization because multiple transmissions undertaken by cooperative systems may not be synchronized in time and/or frequency. With synchronization errors, conventional space-time (ST) codes may not be directly applicable any longer. To tackle the problem of timing synchronization, space-frequency (SF) coded orthogonal frequency division multiplexing (OFDM) cooperative systems have recently been proposed to achieve asynchronous diversity due to their insensitivity to timing errors. However, these systems still need to face the problem of multiple carrier frequency offsets (CFOs). Since each node in a cooperative system is equipped with its own oscillator, the received signals from different relay nodes may have multiple CFOs which cannot be compensated simultaneously at the destination node. For SF coded OFDM cooperative systems, this problem becomes more complicated because CFOs can lead to inter-carrier interference (ICI). To address this challenge, in this thesis we consider the signal detection problem in cooperative systems having multiple CFOs. / First, we investigate the effect of multiple CFOs on two classic ST codes. They are delay diversity and the Alamouti code. For delay diversity, we find that both its achieved diversity order and diversity product are not decreased by multiple CFOs arising from maximum-likelihood (ML) detection. For the Alamouti code, the diversity product may be decreased by multiple CFOs. In the worst case situation, full diversity order 2 cannot be achieved. / For deeper insights into the SF coded communication system with multiple CFOs, we then carry out diversity analysis. By treating the CFOs as part of the SF codeword matrix, we show that if all the absolute values of normalized CFOs are less than 0.5, then the full diversity order for the SF codes are not affected by the multiple CFOs in the SF coded OFDM cooperative system. We further prove that this full diversity property can still be preserved if the zero forcing (ZF) method is used to equalize the multiple CFOs. This method, by some reasonable approximations, is actually equivalent to the MMSE-F detection method. To improve the robustness of the SF codes to multiple CFOs, we propose a novel permutation method. With this method, the achieved diversity order of SF codes remains the same even when the absolute values of normalized CFOs are equal to or greater than 0.5. To reduce computational complexity, we further propose two full diversity achievable detection methods, namely the ZF-ML-Zn and ZF-ML-PIC detection methods, which are suitable for the case when the ICI matrix is singular. / In summary, in this study, we demonstrate that with proper design, the SF coded OFDM approach can be made robust to both timing errors and CFOs in a cooperative communication system. / Since OFDM systems are robust to timing errors, we turn to an SF coded cooperative communication system with multiple CFOs, where the SF codes are rotational based and can achieve both full cooperative and full multipath diversity orders. We begin with the traditional way of ICI mitigation. To preserve the performance of the SF code, we suggest increasing the SINR of each subcarrier but not equalizing the SF precoding matrix. By exploiting the structure of the SF codes, we propose three signal detection methods to deal with the multiple CFOs problem in SF coded OFDM systems. They are the minimum mean-squared filtering (MMSE-F) method, the two-stage simple frequency shift Q taps (FS-Q-T) method, and the multiple fast Fourier transform (M-FFT) method, all of which offer different tradeoffs between performance and computational complexity. Our simulation results indicate that the proposed detection methods perform well as long as the CFOs between nodes are small. / Tian, Feng. / Adviser: Ching Pak-Chung. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0559. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 146-160). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Multiple-input multiple-output (MIMO) systems are a mature technology that has been incorporated into current wireless broadband standards to improve the channel capacity and link reliability. Nevertheless, due to the continuous increasing demand for wireless data traffic new strategies are to be adopted. Very large MIMO antenna arrays represents a paradigm shift in terms of theory and implementation, where the use of tens or hundreds of antennas provides significant improvements in throughput and radiated energy efficiency compared to single antennas setups. Since design constraints limit the number of usable antennas, virtual systems can be seen as a promising technique due to their ability to mimic and exploit the gains of multi-antenna systems by means of wireless cooperation. Considering these arguments, in this work, energy efficient coding and network design for large virtual MIMO systems are presented. Firstly, a cooperative virtual MIMO (V-MIMO) system that uses a large multi-antenna transmitter and implements compress-and-forward (CF) relay cooperation is investigated. Since constructing a reliable codebook is the most computationally complex task performed by the relay nodes in CF cooperation, reduced complexity quantisation techniques are introduced. The analysis is focused on the block error probability (BLER) and the computational complexity for the uniform scalar quantiser (U-SQ) and the Lloyd-Max algorithm (LM-SQ). Numerical results show that the LM-SQ is simpler to design and can achieve a BLER performance comparable to the optimal vector quantiser. Furthermore, due to its low complexity, U-SQ could be consider particularly suitable for very large wireless systems. Even though very large MIMO systems enhance the spectral efficiency of wireless networks, this comes at the expense of linearly increasing the power consumption due to the use of multiple radio frequency chains to support the antennas. Thus, the energy efficiency and throughput of the cooperative V-MIMO system are analysed and the impact of the imperfect channel state information (CSI) on the system's performance is studied. Finally, a power allocation algorithm is implemented to reduce the total power consumption. Simulation results show that wireless cooperation between users is more energy efficient than using a high modulation order transmission and that the larger the number of transmit antennas the lower the impact of the imperfect CSI on the system's performance. Finally, the application of cooperative systems is extended to wireless self-backhauling heterogeneous networks, where the decode-and-forward (DF) protocol is employed to provide a cost-effective and reliable backhaul. The associated trade-offs for a heterogeneous network with inhomogeneous user distributions are investigated through the use of sleeping strategies. Three different policies for switching-off base stations are considered: random, load-based and greedy algorithms. The probability of coverage for the random and load-based sleeping policies is derived. Moreover, an energy efficient base station deployment and operation approach is presented. Numerical results show that the average number of base stations required to support the traffic load at peak-time can be reduced by using the greedy algorithm for base station deployment and that highly clustered networks exhibit a smaller average serving distance and thus, a better probability of coverage.

This thesis addresses and identifies outstanding challenges associated with the Multi user massive Multiple-Input Multiple-Output (MU massive MIMO) transmission, whereby various system scenarios have been considered to tackle these challenges. First, for a single cell scenario, the uplink effective capacity under statistical exponent constraints, the asymptotic error and outage probabilities in a multi user massive MIMO system are provided. The proposed approach establishes closed form expressions for the aforementioned metrics under both perfect and imperfect channel state information (CSI) scenarios. In addition, expressions for the asymptotically high signal-to-interference ratio (SIR) regimes are established. Second, the statistical queueing constraints, pilot contamination phenomenon and fractional power control in random or irregular cellular massive MIMO system are investigated, where base station locations are modelled based on the Poisson point process. Specifically, tractable analytical expressions are developed for the asymptotic SIR coverage, rate coverage and the effective capacity under the quality of service statistical exponent constraint. Laplace transform of interference is derived with the aid of mathematical tools from stochastic geometry. Simulation outcomes demonstrate that pilot reuse impairments can be alleviated by employing a cellular frequency reuse scheme. For example, with unity frequency reuse factor, we see that 40% of the total users have SIR above −10.5dB, whereas, with a reuse factor of 7, the same fraction of users have SIR above 20.5dB. In addition, for a certain parameters setting, the coverage probability in the lower 50th percentile can be maximized by adjusting power compensation fraction between 0.2 and 0.5. Also, for SIR threshold of 0dB, allocating 0.25 fraction of uplink transmit power can achieve approximately 6% improvement in coverage probability in the cell edge area compared to constant power policy and about 14% improvement compared to the full channel-inversion policy. Third and last, motivated by the powerful gains of incorporating small cells with macro cells, a massive MIMO aided heterogeneous cloud radio access network (H-CRAN) is investigated. More specific, based on Toeplitz matrix tool, tractable formulas for the link reliability and rate coverage of a typical user in H-CRAN are derived. Numerical outcomes confirm the powerful gain of the massive MIMO for enhancing the throughput of the H-CRAN while small remote radio heads (RRH cells) are capable of achieving higher energy efficiency.