Machine Learning Meets Communication Networks: Current Trends and Future Challenges

The growing network density and unprecedented increase in network traffic, caused by the massively expanding number of connected devices and online services, require intelligent network operations. Machine Learning (ML) has been applied in this regard in different types of networks and networking technologies to meet the requirements of future communicating devices and services. In this article, we provide a detailed account of current research on the application of ML in communication networks and shed light on future research challenges. Research on the application of ML in communication networks is described in: i) the three layers, i.e., physical, access, and network layers; and ii) novel computing and networking concepts such as Multi-access Edge Computing (MEC), Software Defined Networking (SDN), Network Functions Virtualization (NFV), and a brief overview of ML-based network security. Important future research challenges are identified and presented to help stir further research in key areas in this direction

Dynamic nonlinear behavioral modeling and adaptive predistortion for RF transmitters

Motivation -- Nonlinear dynamic behaviour, two-and three-box models -- Objectives and outline of the thesis -- Two-Box models, de-embedding nonlinearities and dynamic memory effects -- Transmitter prototype -- Hammerstein and Wiener model construction -- Three-box oriented nonlinear model -- Three-box model's two-stage identification procedure -- Adaptive predistortion construction using single tone signal -- Hypothetical model and adaptive predistortion -- Construction of the complete predistorted system with a two-box model -- Complete predistorted system and linearization validation with CDMA signal

Journal of Telecommunications and Information Technology

kwartalni

2 GHz +14 dBm CMOS power amplifier for Low Power Wide Area Networks

Abstract. The design of a radiofrequency power amplifier (RF PA) for narrowband low-power wide area networks is presented in this thesis. Particularly, this RF PA is compliant with the 3GPP TS 36.101 standard for a NB1 device within the Power Class 6. To minimize silicon area consumption, this CMOS RF PA employs a single-ended single-stage topology, avoiding inter-stage matching network inductors and output baluns. This RF PA produces +14 dBm of output power with a PAE of 25% and an EVM better than 4% (−28 dB). Also, its out-of-band and spurious emissions satisfy the standard specifications with a large margin. Furthermore, it provides high ruggedness, tolerating an antenna mismatch with a VSWR of 8:1

Caracterização não-linear de agregados de antenas para aplicações 5G

The present mobile scenario demands are stretching the existing telecom infrastructure to the limit. New technologies centred around antenna arrays and spatial multiplexing have been proposed to overcome the challenges imposed by these demands. This work overviews the mobile scenario, scrutinizing demands, presented solutions, challenges and the industry’s perspective of the Fifth Generation of mobile communications. From a careful analysis, the 5G’s most critical radio frequency hardware issues are detailed, and a long-term approach to address them is presented. On the short-term the work focuses on antenna characterization, because antennas are a central part of future wireless communications. Initially, basic antenna concepts are presented, then emphasis is given to microstrip antennas, going through all the steps of designing, optimizing and measuring a rectangular microstrip antenna and an eight element linear antenna array for 5.67GHz. Array features such as scanning and source synthesis are also explored. Finally, the impact of signal nonlinear distortion on the antenna array pattern is studied, aiming to expand state-of-the-art knowledge on how signal nonlinear distortion can limit spatial multiplexing. A theoretical model of the phenomenon is proposed and validated both by electromagnetic simulation and measurements.As crescentes exigências das redes móveis estão a levar a infraestrutura de telecomunicações ao seu limite. Novas tecnologias centradas em agregados de antenas e multiplexagem espacial têm sido propostas para ultrapassar os desafios impostos por tais exigências. Este trabalho apresenta uma visão abrangente das redes móveis atuais, escrutinando as suas exigências, as soluções apresentadas, os desafios adjacentes, bem como a opinião da indústria. Os problemas mais crı́ticos do hardware de radio frequência para a quinta geração de redes móveis são apurados a partir de uma análise detalhada do cenário das redes sem fios, sendo apresentado um plano a longo prazo para abordar estas problemáticas. A curto prazo o trabalho foca-se em caracterização de antenas, visto que as antenas são um ponto central nas comunicações sem fios do futuro. Inicialmente são apresentados conceitos básicos sobre antenas, dando-se de seguida ênfase às antenas microstrip, sendo apresentado todo o processo de sı́ntese, otimização e caracterização de uma antena microstrip retangular e de um agregado de antenas linear de oito elementos com frequência de operação 5.67GHz. Neste âmbito, algumas propriedades dos agregados, como o varrimento angular do feixe eletromagnético e técnicas de sı́ntese de fonte eletromagnética, são também exploradas. Finalmente, apresenta-se um estudo sobre o impacto que a distorção não linear de sinal pode ter no diagrama de radiação do agregado de antenas. O objetivo é expandir os conhecimentos do estado-da-arte acerca das limitações que a distorção não linear pode impor na multiplexagem espacial. Neste sentido, um modelo teórico descritivo deste fenómeno é proposto e validado por simulação eletromagnética e por medições experimentais.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Broadband Linearity-Enhanced Doherty Power Amplifier Design Techniques for 5G Sub-6 GHz Applications

The recently deployed fifth generation (5G) cellular networks represent a significant technological advancement over fourth generation (4G) networks. Specifically, new 5G frequency bands were allocated at sub-6 GHz and instantaneous signal bandwidths were increased to satisfy the rapidly growing needs for increased data rates. Furthermore, 5G uses more complex modulation schemes to improve spectrum efficiency. Finally, 5G introduced massive multiple input multiple output (MIMO), where multiple transceivers are used to direct the signal towards specific users, increasing channel capacity. Conventional power amplifiers (PAs) are not suitable for 5G applications due to the increased signal and system complexity. For example, the Doherty power amplifier (DPA) technique is popular since DPAs can efficiently amplify signals with complex modulation schemes, but conventional DPAs have narrow bandwidth and poor linearity that preclude their use in 5G systems. This motivated research into DPA bandwidth and linearity improvements for use in 5G networks. This work focuses on bandwidth and linearity enhancement for sub-6 GHz DPAs realized using discrete components on a printed circuit board (PCB). Bandwidth is improved using broadband architectures for the DPA output combiner network (OCN), the absorption of drain parasitics, and broadband input matching network (IMN) design. Linearity is enhanced by proper drain biasing network design, and careful selection of transistor source impedances. A 3.3–5.0 GHz DPA using these techniques is designed and fabricated. Under wideband modulated signal excitation, the DPA offers very good linearity with appropriate digital predistortion (DPD). A 2×2 array of DPAs is evaluated in fully digital MIMO setup using a 2×2 antenna array. The DPA array achieves excellent linearity characteristics under 100 MHz signals and use of dual-input single-output (DISO) DPD. The DPA remains the ideal choice in 5G MIMO systems when compared to the class AB PA since it can maintain a higher average drain efficiency and similar linearity

Faculty of Engineering and Design. Research Review

STUDENTS AND ACADEMICS - This publication introduces you to the department or school and then each faculty member’s research areas, research applications, and their most recent activities. A comprehensive index can be found at the back of this publication to help guide you by specific areas of interest, as well as point out interdisciplinary topics and researchers. INDUSTRY LEADERS - This publication includes information regarding specific facilities, labs, and research areas of departments and schools as well as individual faculty members and researchers. A comprehensive index can be found at the back of this publication to help guide you by specific areas of interest, as well as point out interdisciplinary topics and researchers