In centralized radio access network (C-RAN) architecture, the base-band unit (BBU) is connected to one or more remote radio units (RRUs) via a fronthaul (FH) interface. Upgrading base station antennas in C-RAN to support massive multiple-input multiple-output (MIMO) technology can improve network spectral efficiency and largely boost the capacity of the 5G system. Those great benefits also introduce new challenges to the FH interface since the required FH capacity increases proportionally to the number of transceiver units (TXRUs) for traditional receiver processing at the BBU. To reduce the FH link load, different base-band splitting options between RRUs and BBU are considered in practical C-RAN networks. In this project, we investigate three beamforming algorithms (MRC, DFT and Enhanced) which are expected to reduce the number of streams on FH link, and evaluate their performance for single-user MIMO in different mobility scenarios via system-level simulations. The results show that we successfully reach the goal of reducing the number of streams to one-fourth the number of TXRUs meanwhile maintaining relatively good performance. Additionally, we observe that the Enhanced algorithm performs the best in majority of scenarios. / I en centraliserad nätverksarkitektur för radioåtkomst är basbandsenheten ansluten till en eller flera fjärrradionheter via ett fronthaul-gränssnitt. Genom att uppgradera basstationsantennerna i C-RAN för att stödja massiv multipel input-multipel output-teknik kan man förbättra nätverkets spektraleffektivitet och till stor del öka kapaciteten i 5G-systemet. Dessa stora fördelar medför också nya utmaningar för FH-gränssnittet eftersom den nödvändiga FH-kapaciteten ökar proportionellt mot antalet sändare för traditionell mottagarbearbetning vid BBU. För att minska belastningen på FH-länken övervägs olika alternativ för uppdelning av basbandet mellan RRUs och BBU i praktiska C-RAN-nät. I det här projektet undersöker vi tre strålformningsalgoritmer (MRC, DFT och Enhanced) som förväntas minska antalet strömmar på FH-länken och utvärderar deras prestanda för single-user MIMO i olika mobilitetsscenarier med hjälp av simuleringar på systemnivå. Resultaten visar att vi lyckas uppnå målet att minska antalet strömmar till en fjärdedel av antalet TXRU:s samtidigt som vi behåller en relativt god prestanda. Dessutom kan vi konstatera att den förbättrade algoritmen presterar bäst i de flesta scenarier.

Multi-User Multi-Input Multi-Output (MU-MIMO) systems are considered to be the sustainable technologies of the current and future of the upcoming wireless and mobile networks generations. The perspectives of these technologies under several scenarios is the focus of the present thesis. The initial system model covers the MU-MIMO, especially in the massive form that is considered to be the promising ideas and pillars of the 5G network. It is observed that the optimal number of users should be served in the time-frequency resource even though the maximum limitation of the MU-MIMO is governed by the total receiving antennas (K) is less than or equal to the base station antennas (M). The system capacity of the massive MIMO (mMIMO) under perfect channel state information (CSI) of uncorrelated channel is investigated and studied. Two types of precoders were applied, one is directly based on channel inversion, and the other uses the Eigen decomposition that is derived subject to the signal to a leakage maximization problem. The two precoders show a degree of equivalency under certain assumptions for the number of antennas at the user end. The convex optimization of multi-antenna networks to achieve the design model of optimum beamformer (BF) based on the uniform linear array (ULA) is studied. The ULA is selected for its simplicity to analyse many scenarios and its importance to match the future network applied millimetre wave (mmWave) spectrum. The maximum beams generated by the ULA are explored in terms of several physical system parameters. The duality between the MU-MIMO and ULA and how they are related based on beamformer operation are detailed and discussed. Finally, two approaches for overloaded systems are presented when the availability of massive array that is not guaranteed due to physical restrictions since the existence of a large number of devices will result in breaking the dimension rule (i.e., K ≤ M). As a solution, a low complexity users selection algorithm is proposed. The channel considered is uncorrelated with full and perfect knowledge at the BS. In particular, these two channel conditions may not be available in all scenarios. The CSI may be imperfect, and even the instantaneous form does not exist. A hybrid precoder between the mixed CSI (includes imperfect and statistical) and rate splitting approach is proposed to deal with an overloaded system under a low number of BS antennas. / Ministry of Higher Education and Scientific Research of Iraq

Radar technology is widely used in today´s society, whether it is the localisation and identification of aircraft in air traffic control systems, ships in harbour management systems, or the weather forecast presented on the news. In military applications, such as in fighter jets or missile lock-on systems, the speed at which the radar processes incoming data is essential to ensure a successful outcome. These applications need more powerful execution platforms, such as Application-Specific Integrated Circuits (ASICs) or Field-Programmable Gate Array (FPGAs) to run at the required speed. Radar technology manufacturers face both high development costs and long development cycles when designing, redesigning and developing these powerful execution platforms. A solution to these problems could be to design and develop the system in software before implementing it on the specialised ASIC and FPGA ships. As a step toward creating a software-based processing chain for radar systems, this thesis amide to investigate whether General-Purpose Graphical Processing Units (GPUs) could be used to develop and run beamforming applications in real-time at a sample rate of 100 MHz. To achieve this goal, the Bartlett and MVDR Beamforming algorithms were analysed and implemented in the Computer Unified Device Architecture (CUDA) programming framework on an NVIDIA GeForce RTX 2080 super GPU. The algorithms´ parallelisable elements were considered before implementation, and then implemented to fit with the CUDA programming model. In the end, both beamformers´ primary acceleration methods is using the cuBLAS library for linear algebra operations. The results of this study show that beamforming in real-time is not possible on a GPU when processing a signal sampled at 100 MHz. However, the GPU used just passed its third anniversary since release, and NVIDIA has released subsequent generations of GPUs with significant (>100%) performance increases. Future work on this area could include trying the implementations on more recent GPUs or implementing other beamforming algorithms on GPUs. / Radarteknik används inom flera områden idag. Bland annat för lokalisering och identifiering av flygplan och fartyg i flyglednings- och hamnledningssystem, eller för att skapa väderprognosen som presenteras på nyheterna. För militära tillämpningar, till exempel i stridsflygplan eller missillåsningssystem, är behandlingshastigheten av inkommande data avgörande för att korrekt information ska visas. Dessa användningsområden kräver kraftfulla chip, såsom ASICs eller FPGAer, för att uppnå den exekveringshastighet, kompakthet och energieffektivitet som krävs. Såväl höga utvecklingskostnader som långa utvecklingscykler uppstår för radartillverkare när de designar och utvecklar dessa kraftfulla chip. En lösning på de långa cyklerna och höga kostnaderna kan vara att designa och utveckla systemet i mjukvara på en högre abstraktionsnivå innan det implementeras på de specialiserade ASIC- och FPGA-chipen. I ett steg mot att skapa en mjukvarubaserad signalbehandligsskedja gör radarsystem, syftar detta examensarbete till att undersöka om GPUer skulle kunna användas för att utveckla och exekvera beamformingapplikationer i realtid med en samplingsfrekvens på 100 MHz. För att uppnå detta mål analyserades och  implementerades beamformingalgoritmerna Bartlett och MVDR i CUDA på en NVIDIA GeForce RTX 2080 Super GPU. De element av algoritmerna som går att parallellisera undersöktes, följt av implementation i CUDAs programmeringsmodell. Den primära accelerationsmetoden för båda beamformingalgoritmerna är att använda cuBLAS-biblioteket för linjär algebraoperationer. Resultaten av denna studie visa att beamforming i realtid inte är möjligt på en GPU vid behandling av en signal samplad i 100 MHz. Den GPU som användes har nyligen passerat sin tredje årsdag sedan lansering, och NVIDA har släppt efterföljande GPU-generationer med avsevärda (>100%) prestandaökningar- I framtida arbeten på området föreslås att testa implementationerna på nyare GPUer, implementera beamformers i t.ex. OpenGL, implementera andra beamformingalgoritmer i CUDA.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / A Synthetic Beamforming antenna was built for Airborne Telemetry. Low-Noise Block-converters translated RF to IF suitable for direct analog-to-digital conversion. Then all telemetry functions were performed digitally via parallel FPGAs for 10 independent sources. Monopulse tracking and optimal diversity combination was performed using 4 antenna quadrants at two orthogonal polarizations. Novel estimation approaches drove digital demodulation, symbol- and bit- synchronization. Final telemetry outputs include: digital, analog (video), and analog IF (e.g., for downlink relay). This program has incubated several concepts that we believe have the combined potential to significantly improve the future of telemetry.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Robust adaptive beamforming using worst-case performance optimization is developed in recent years. It had good performance against array response errors, but it cannot reject strong interferences. In this paper, we propose a scheme for robust adaptive beamforming with broad nulls to reject strong interferences. We add a quadratic constraint to suppress the power of the array response over a spatial region of the interferences. The optimal weighting vector is then obtained by minimizing the power of the array output subject to quadratic constrains on the desired signal and interferences, respectively. We derive the formulations for the optimization problem and solve it efficiently using Newton recursive algorithm. Numerical examples are presented to compare the performances of the robust adaptive beamforming with no null constrains, sharp nulls and broad nulls. The results show its powerful ability to reject strong interferences.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / The next generation Digital Beamforming Array (DBFA) requires techniques beyond the existing adaptive processing and optimization approaches. By utilizing neural network processing and genetic algorithms that mimic complicated natural processes, such as the brain and natural selection, new and superior Antenna Arrays can be designed. The use of Neural Networks and Genetic Algorithms combined with the existing techniques for DBFAs can yield the ultimate in “real-time,” “smart” antenna performance. Cost is significantly reduced by; allowing large manufacturing tolerances, the use of inexpensive components, and correcting by neural network techniques. This paper describes the technology and proposes a practical application of the technique to design a DBFA to track and transmit/receive telemetry from a shipboard vertically launched medium range missile.

The complex relationship between array gain patterns and microphone distributions limits the application of traditional optimization algorithms on irregular arrays, which show enhanced beamforming performance for human speech capture in immersive environments. This work analyzes the relationship between irregular microphone geometries and spatial filtering performance with statistical methods. Novel geometry descriptors are developed to capture the properties of irregular microphone distributions showing their impact on array performance. General guidelines and optimization methods for regular and irregular array design are proposed in immersive (near-field) environments to obtain superior beamforming ability for speech applications. Optimization times are greatly reduced through the objective function rules using performance-based geometric descriptions of microphone distributions that circumvent direct array gain computations over the space of interest. In addition, probabilistic descriptions of acoustic scenes are introduced to incorporate various levels of prior knowledge for the source distribution. To verify the effectiveness of the proposed optimization methods, simulated gain patterns and real SNR results of the optimized arrays are compared to corresponding traditional regular arrays and arrays obtained from direct exhaustive searching methods. Results show large SNR enhancements for the optimized arrays over arbitrary randomly generated arrays and regular arrays, especially at low microphone densities. The rapid convergence and acceptable processing times observed during the experiments establish the feasibility of proposed optimization methods for array geometry design in immersive environments where rapid deployment is required with limited knowledge of the acoustic scene, such as in mobile platforms and audio surveillance applications.

Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-N, interferometric arrays. The computational demands of digital correlators required by these arrays present a significant challenge. These demands stem from the treatment of radio telescopes as collections of two-element interferometers, which results in the need to multiply O(N²) pairs of antenna signals in an N-element array. Given the unparalleled flexibility offered by modern digital processing systems, it is apt to consider whether a different way of treating the signals from antennas in an array might be fruitful in current and future radio telescopes. Such methods potentially avoid the unfavourable N² scaling of computation rate with array size. In this thesis I examine the prospect of using direct-imaging methods to map the sky without first generating correlation matrices. These methods potentially provide great computational savings by creating images using efficient, FFT-based algorithms. This thesis details the design and deployment of such a system for the Basic Element of SKA Training II (BEST-2) array in Medicina, Italy. Here the 32-antenna BEST-2 array is used as a test bed for comparison of FX correlation and direct-imaging systems, and to provide a frontend for a real-time transient event detection pipeline. Even in the case of traditional O(N²) correlation methods, signal processing algorithms can be significantly optimized to deliver large performance gains. In this thesis I present a new mechanism for optimizing the cross-correlation operation on Field Programmable Gate Array (FPGA) hardware. This implementation is shown to achieve a 75% reduction in multiplier usage, and has a variety of benefits over existing optimization strategies. Finally, this thesis turns its focus towards The Square Kilometre Array (SKA). When constructed, the SKA will be the world's largest radio telescope and will comprise a variety of arrays targeting different observing frequencies and science goals. The low-frequency component of the SKA (SKA-low) will feature ~250,000 individual antennas, sub-divided into a number of stations. This thesis explores the impact of the station size on the computational requirements of SKA-low, investigating the optimal array configuration and signal processing realizations.

Phased array radar systems employ multiple antennas to create a radar beam that can be steered electronically. By manipulating the relative phase values of feeding signals among different antennas, the effective radiation pattern of the array can be synthesized to enhance the main lobe in a desired direction while suppressing the undesired side lobes in other directions. Hence the radar scanning angles can be electronically controlled without employing the bulky mechanical gimbal structure, which can significantly reduce radar system size, weight and power consumption. In recent years, phased array technologies have received great attentions and are explored in developing many new applications, such as smart communication systems, military radars, vehicular radar, etc. Most of these systems are narrow band systems, where the phase delays are realized with narrow band phase shifter circuits. For the impulse ground penetrating radar however, its operating frequency spans an ultrawide bandwidth. Therefore the traditional phase shifters are not applicable due to their narrow band nature. To resolve the issue, in this study, a true time delay approach is explored which can precisely control time delays for the feeding pulse signals among different antennas in the array. In the design, an on chip programmable delay generator is being developed using Global Foundry 0.18 µm 7 HV high voltage CMOS process. The time delay control is realized by designing a programmable phase locked loop (PLL) circuit which can generate true time delays ranging from 100 ps (picoseconds) to 500 ps with the step size of 25 ps. The PLL oscillator's frequency is programmable from 100MHz to 500MHz through two reconfigurable frequency dividers in the feedback loop. As a result, the antenna beam angle can be synthesized to change from 9.59° to 56.4° with a step of 2.75°, and the 3dB beamwidth is 10°. The power consumption of the time delay circuit is very low, where the supply voltage is 1.8V and the average current is as low as 472uA.

Approved for public release; distribution in unlimited. / a beam towards the UAV. A simulation model was developed and implemented in MATLAB programming language to study the effectiveness of beamforming using sensor clusters for establishing a communication link to the UAV. Results showed that the antenna main lobe remained relatively unchanged in the presence of position errors and sensor node failures or when the density of the sensor nodes changed. Additionally, the maximum average power gain of the main lobe can be increased by increasing the density of the sensor cluster, thereby increasing the transmission range between the sensor clusters and the UAV. / Civilian, Singapore Ministry of Defense