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.

As diverse and data-heavy underwater applications emerge, demanding requirements are further imposed on underwater wireless communication systems. Future underwater wireless communication networks might consist of both mobile and stationary nodes which exchange data such as control, telemetry, speech, and video signals among themselves as well as a central node located at a ship or onshore. The submerged nodes, which can, for example, take the form of an autonomous underwater vehicle/robot or diver, can be equipped with various sensors, sonars, video cameras, or other types of data acquisition instruments. Innovative physical layer solutions are therefore required to develop efficient, reliable, and high-speed transmission solutions tailored for challenging and diverse requirements of underwater applications. Building on the promising combination of multi-carrier and cooperative communication techniques, this dissertation investigates the fundamental performance bounds of cooperative underwater acoustic (UWA) communication systems taking into account the inherent unique characteristics of the UWA channel. We derive outage probability and capacity expressions for cooperative multi-carrier UWA systems with amplify-and-forward and decode-and-forward relaying. Through the derived expressions, we demonstrate the effect of several system and channel parameters on the performance. Furthermore, we investigate the performance of cooperative UWA systems in the presence of non-uniform Doppler distortion and propose receiver designs to mitigate the degrading Doppler effects.

In this paper, the heuristic rules are proposed to derive the rephasing strategy of laterals and distribution transformers to improve the three phase unbalance of distribution systems. The distribution feeder network has been obtained by retrieving the attribute data of distribution components from the database of outage management system (OMS) in Taipower. The topology process and node reduction have also been executed to identify the network configuration and to prepare the input data for load flow analysis. With the monthly energy consumption of customers served by each transformer, which has been retrieved from the Customer Information System (CIS), the hourly loading of each distribution transformer can be derived. By performing the three phase load flow analysis, the three phase currents and neutral current of each primary trunk line section and each lateral can be calculated. The heuristic rule is employed to determine the phase adjustment strategy laterals and distribution transformers for rephasing to achieve three phase balancing. In order to demonstrate the effectiveness of the proposed methodology for three phase balancing, two practical distribution feeders in Taipower Fengshan District are selected for simulation. After rephasing the distribution transformers and laterals proposed by this paper, the three phase currents and netural of the test feeders have been collected. By companing to the neutral current before rephasing, it is found that the neutral current of test feeders have been reduced significantly and there phase balancing has been obtained by executing the proposed strategy derived using the heuristic rule.

Unbalanced operation of distribution feeders not only affects equipment utilization, voltage level and system protection, but it also increases extra energy losses. This leads to a deterioration of service quality, reliability and operation efficiency of a distribution system. This dissertation analyzes the problems of unbalanced three-phase distribution feeders, and offers potential solutions. Due to the voluminous data involved in a distribution system, analyzing the system by retrieving system data from paper maps is tedious and difficult. Thus, this dissertation uses data from the already constructed Outage Management System (OMS) of Taiwan Power Company (Taipower) to support distribution feeder three-phase unbalance analysis. The distribution feeder network was obtained by retrieving the connectivity table and attribute data of distribution components from the database of OMS. The topology process and node reduction were executed to identify the network configuration and to prepare the input data for load flow analysis. The hourly loading of each distribution transformer was derived using data of monthly energy consumption of customers served by each transformer, as retrieved from the Customer Information System (CIS), and the typical daily load patterns of customer classes. By performing three-phase load flow analysis, phase currents and neutral current of each primary trunk line section and each lateral could be calculated. Finally, an expert system is proposed to establish the rephasing strategy of laterals and distribution transformers to improve the imbalance of the three phases of the unbalanced distribution feeders. The heuristic rules adopted by distribution engineers are incorporated in the knowledge base of the expert system in the problem-solving process. The neutral current reduction algorithm is developed to support the inference engine to derive the rephasing strategy to reduce the neutral current of distribution feeder. In doing so, customer service interruption due to unexpected tripping of low energy over current relay (LCO) can be prevented, and furthermore the customer service interruption costs and labor costs to implement the rephasing strategy can be justified by the reduced power loss. To demonstrate the effectiveness of this proposed methodology in improving the three-phase unbalance of the distribution feeders, two actual distribution feeders in the Taipower Fengshan District were selected for computer simulation. After Taipower engineers implement the proposed rephasing strategies, the data of phase currents and neutral current of test feeders were collected from the SCADA system of Distribution Dispatch Control Center (DDCC). By comparing to the neutral current of test feeders before rephasing, it is concluded that the proposed rephasing strategy is effective in achieving three-phase balance of the distribution feeders after executing the rephasing of laterals and distribution transformers.

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At the present time, wireless sensor networks are becoming more and more  common and energy consumption is a key factor in the deployment and  maintenance of these networks. This thesis compares non-SFN multi-hop and  a single frequency network (SFN) or cooperative diversity algorithms with  respect to the energy consumed by the nodes. Since the nodes have limited  power capacity it is extremely important to have an efficient algorithm. In  addition, the behaviour of the network when SFN is employed must be  studied and advice offered with regards to improvements in order to achieve  preferential results. The effect on the network regarding macro diversity is  positive but, the battery energy consumption is still higher and has a drainage  effect on the network for simple multi-hop. The report will include  background information regarding mobile ad-hoc networks and the  relationship with cooperative diversity. It will also deal with how different  algorithms affect the energy consumption in multi-hop networks. Simulations  will also be presented in Matlab plots for two single frequency network  scenarios against a simple multi-hop regarding node energy during the  network discovery and decline. Results will include comparative figures which  are followed by a discussion concerning the simulation results and its effects.  The applications for wireless sensor networks include area monitoring,  environmental monitoring, data logging, industrial monitoring, agriculture  and the idea can additionally be used for wireless radio and TV distribution.  The simulations have been conducted for cooperative diversity algorithms  (SFN-A and SFN-D) against an algorithm which does not use cooperative  diversity in Matlab. The node energy consumption is compared for both  scenarios with regards to both  network reachability and decline. The node  power is analysed during the reachability of the network from the start to  attaining 100% of the discovered network. During network decline, the  behaviour of the node energy is studied for algorithms with SFN-A, SFN-D  and non SFN.  Also, the number of times node transmission occurs with  regards to  node discovery is also analysed.

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As diverse and data-heavy underwater applications emerge, demanding requirements are further imposed on underwater wireless communication systems. Future underwater wireless communication networks might consist of both mobile and stationary nodes which exchange data such as control, telemetry, speech, and video signals among themselves as well as a central node located at a ship or onshore. The submerged nodes, which can, for example, take the form of an autonomous underwater vehicle/robot or diver, can be equipped with various sensors, sonars, video cameras, or other types of data acquisition instruments. Innovative physical layer solutions are therefore required to develop efficient, reliable, and high-speed transmission solutions tailored for challenging and diverse requirements of underwater applications. Building on the promising combination of multi-carrier and cooperative communication techniques, this dissertation investigates the fundamental performance bounds of cooperative underwater acoustic (UWA) communication systems taking into account the inherent unique characteristics of the UWA channel. We derive outage probability and capacity expressions for cooperative multi-carrier UWA systems with amplify-and-forward and decode-and-forward relaying. Through the derived expressions, we demonstrate the effect of several system and channel parameters on the performance. Furthermore, we investigate the performance of cooperative UWA systems in the presence of non-uniform Doppler distortion and propose receiver designs to mitigate the degrading Doppler effects.

Multihop routing is an effective method for establishing connectivity between the nodes of a network. End-to-end outage probability and total power consumption are applied as the optimization criteria for routing protocol design in multihop networks based on the local channel state information measurement at the nodes of a network. The analysis shows that employing instantaneous channel state information in routing design results in significant performance improvement of multihop communication, e.g., achieving full diversity order when the optimization criterion is outage performance. The routing metrics derived from the optimization problems cannot be optimized in a distributed manner. Establishing an alternate framework, the metrics obtained are converted into new composite metrics, which satisfy the optimality and convergence requirements for implementation in distributed environments. The analysis shows that the running time of the proposed distributed algorithm is bounded by a polynomial. / Communications

Spectral efficiency is one of the most important measures of the performance of wireless communication systems owing to scarcity and cost of the radio spectrum. The increase in spectral efficiency provides higher data rates to the user, lower network cost to the operator, coverage extension and higher service reliability as well. Intercell interference due to frequency reuse is one of the key impairments in wireless systems. Multiple-input multiple-output (MIMO) technique has been developed to enhance the desired signal power (and hence mitigating the effects of intercell interference) and with employing simple linear signal processing technique, can strongly mitigate the interference resulting from co-channel users. This technique is mainly used to achieve spatial diversity for boosting the communication link reliability by combating fading, and providing spatial multiplexing to increase data rates without extra bandwidth by exploiting multipath. Distributed antenna system (DAS) has recently gained substantial interest due to its ability to reduce transmitted power thereby lowering the out-of-cell interference effects, maximise the coverage and improve the spectral efficiency. The combination of MIMO techniques with DAS, so-called distributed MIMO (D-MIMO) systems, is now being exploited and largely succeeded to fulfil the services of the fourth generation (4G) wireless systems. Very recently, one of crucial significance approach to reducing the radiated power and improving spectral efficiency to cope with fifth generation (5G) wireless systems is the use of large-scale MIMO (also referred to as massive MIMO) technology, which utilizes a large number of antennas, i.e., tens to hundreds, typically at the base station (BS) side. Presently, in the light of the rapid evolution of wireless systems into 5G, the integration of wireless power transfer (WPT) with newly wireless systems has seen a great deal of attention as a potential solution for powering energy-constrained wireless systems, especially with shortening communication links by emerging new technologies, e.g., D-MIMO and massive MIMO. This thesis is devoted to investigating and comparing the performance of three different MIMO systems. More specifically, the thesis focuses on analysing the spectral efficiency of a comprehensive model of self-powered MU-MIMO systems employing linear ZF technique at the BS for both perfect and imperfect channel state information (CSI) cases. The results demonstrate the impact of practical channel impairments, e.g., spatial correlation, shadowing and co-channel interference (CCI), and system parameters, e.g., the number of BS and user antennas, signal to noise ratio (SNR) and channel estimation error, on the spectral efficiency of the system. Besides, from a spectral efficiency perspective, a proposed model of a combination of MIMO and massive MIMO technologies with DAS in the presence of linear receivers at the processing unit (PU) is considered and compared to a centralised MIMO (CMIMO) system. The obtained results provide a wide range of insights into the effects of system parameters on the spectral efficiency and reveal that the proposed distributed MIMO system outperforms the C-MIMO system. In the context of wireless powered MIMO systems, this work investigates the performance of a power beacon (PB)-assisted wireless powered C-MIMO system, including one multi-antenna BS and a number of single-antenna users powered by randomly deployed PBs in the presence of ZF receiver at the BS. Also, two modes for radiation from the PBs are assumed and compared, one is the beamforming radiation mode (BRM), and the other is the isotropic radiation mode (IRM).