117 research outputs found
Active SLAM: A Review On Last Decade
This article presents a comprehensive review of the Active Simultaneous
Localization and Mapping (A-SLAM) research conducted over the past decade. It
explores the formulation, applications, and methodologies employed in A-SLAM,
particularly in trajectory generation and control-action selection, drawing on
concepts from Information Theory (IT) and the Theory of Optimal Experimental
Design (TOED). This review includes both qualitative and quantitative analyses
of various approaches, deployment scenarios, configurations, path-planning
methods, and utility functions within A-SLAM research. Furthermore, this
article introduces a novel analysis of Active Collaborative SLAM (AC-SLAM),
focusing on collaborative aspects within SLAM systems. It includes a thorough
examination of collaborative parameters and approaches, supported by both
qualitative and statistical assessments. This study also identifies limitations
in the existing literature and suggests potential avenues for future research.
This survey serves as a valuable resource for researchers seeking insights into
A-SLAM methods and techniques, offering a current overview of A-SLAM
formulation.Comment: 34 pages, 8 figures, 6 table
Characteristic Mode Analysis for Multiport Antennas
This thesis focuses on the research to overcome challenges in using the theory of characteristic mode (TCM) for multiport antennas. TCM is particularly useful for exploiting multiple radia tions on the same structure, making it well-suited for dealing with multiport antennas. However, when multiple characteristic modal radiation are activated, many of the previous designs lack a satisfactory frequency band coverage, and the number of antenna ports is often limited. Further more, when applying TCM to analyse the coupling in multiport antennas, the previous methods is not sufficiently clear and does not accommodate a higher number of ports. On the other hand, for a typical dual-polarized Base station (BS) antenna whose radiation pattern is more worthy of concern than coupling and the number of ports, its ground size is typically much larger than the operating wavelength, resulting in a considerable number of irrelevant characteristic modes (CMs) that can disrupt the analysis. In this thesis, several novel research approaches are proposed to overcome the aforementioned challenges and further exploit the application of TCM in multiport antennas. Firstly, a novel planar hexagonal antenna design, developed solely based on the principles of TCM, is proposed. The study centers around the degenerate characteristic mode (CM) pairs of symmetrical shape and their excitation during the design process. By harnessing a higher number of degenerate CM pairs, the proposed design achieves a satisfactory bandwidth among four ports and a satisfying port-to-port isolation. The second proposal introduces a method to evaluate the radiation energy and mutual coupling. This new perspective enables the enhancement of the operating band and isolation in arbitrary multiport antennas. As a result, the design and analysis of multiport antennas become easier. In line with this method, a four-port hexagonal antenna is later proposed. This four-port hexag onal antenna consists of a planar hexagonal plate, vertical tapered baluns, and a feeding network at the ground plane. The antenna exhibits a broadband impedance bandwidth while minimizing mutual coupling among its ports. The last contribution focuses on a dual-port antenna from a BS array. It examines the improvement of radiation performance of the antenna. Instead of the conventional TCM, the sub-structure TCM is employed to isolate the antenna unit from its ground and study the variations of its CMs as the frequency increases. The irreverent CMs are thus eliminated. Modifications have been implemented to enhance the beamwidth stability across the entire band
Využití softwarově definovaného rádia v oblasti SMART technologii
Modern telecommunication systems are rapidly evolving. This rapid development requires constant research and fast prototyping. This dissertation thesis focusses on deployment of software defined radio (SDR) in multiple application areas, including SMART technologies. SDR itself is a tool behind many breakthroughs in modern telecommunications, due to its major adaptability. It offers a comprehensive way of fast prototyping, which rely on suitable software platform. The field of telecommunications is ever-changing, due to the constant pressure on innovation. For this reason, it is desirable to test some of the alternative communication technologies. Visible light communication (VLC) system based on combination of virtual instrumentation and software defined radios was chosen for experimentation. This dissertation focusses on multiple versions of VLC system that were developed over the years. Each version is further discussed, and their advantages and disadvantages are presented. A draft of fourth and newest version is mentioned along with possible directions of the research. Results from multiple application areas are presented, which show the adaptability of the whole platform to different use cases including but not limited to: SMART technologies, automotive, nuclear waste disposal sites, or industry. It is demonstrated that the newest version of the system, which is based on OFDM modulation, can communicate up to 50 meters in closed environments and up to 35 meters in outdoor scenarios. This opens further research directions such as truck platooning or underwater communications.Moderní komunikační systémy jsou jednou z nejrychleji se rozvíjejících oblastí. Takového markantního posunu lze dosáhnout pouze skrze nový vývoj a aplikaci metodiky fast prototypingu. Tato disertace se zaměřuje na nasazení technologie softwarově definovaného rádia (SDR) v různých aplikačních oblastech. Samotné SDR je díky své adaptabilitě nástrojem, který stál na pozadí rozvoje mnoha moderních telekomunikačních systémů. Jedná se o ucelenou platformu pro fast prototyping, která se opírá o robustní softwarovou základnu. Právě telekomunikace jsou oblastí, kde je takové zařízení nedocenitelné, právě kvůli neustálému tlaku na inovace. Právě to je důvodem, proč je vhodné také testovat různé alternativní technologie pro přenos dat. Jednou z takových je komunikace viditelným spektrem světla (VLC), která je náplní této práce. Součástí praktické části je vývoj a popis několika verzí VLC systému založených na virtuální instrumentaci a SDR, které vznikly během autorova studia. Každá verze je samostatně popsána včetně výhod a nevýhod, které poskytují. Součástí je též první náčrt čtvrté verze, která bude součástí budoucího výzkumu. Prezentované výsledky z různých aplikačních oblastí jasně ukazují, že je celou platformu možné použít v různých aplikačních oblastech, včetně SMART technologií, automotive, úložišti jaderného odpadu anebo Průmyslu 4.0. Součástí jsou též výsledky z poslední verze, které dokazují, že je systém ve vnitřních prostorech komunikovat až na vzdálenost 50 metrů, zatímco ve venkovních podmínkách je to 35 metrů. Díky tomu je možné vytyčit nové oblasti výzkumu jako je například platooning (tandemová jízda) anebo podvodní komunikace.450 - Katedra kybernetiky a biomedicínského inženýrstvívyhově
On the Road to 6G: Visions, Requirements, Key Technologies and Testbeds
Fifth generation (5G) mobile communication systems have entered the stage of commercial development, providing users with new services and improved user experiences as well as offering a host of novel opportunities to various industries. However, 5G still faces many challenges. To address these challenges, international industrial, academic, and standards organizations have commenced research on sixth generation (6G) wireless communication systems. A series of white papers and survey papers have been published, which aim to define 6G in terms of requirements, application scenarios, key technologies, etc. Although ITU-R has been working on the 6G vision and it is expected to reach a consensus on what 6G will be by mid-2023, the related global discussions are still wide open and the existing literature has identified numerous open issues. This paper first provides a comprehensive portrayal of the 6G vision, technical requirements, and application scenarios, covering the current common understanding of 6G. Then, a critical appraisal of the 6G network architecture and key technologies is presented. Furthermore, existing testbeds and advanced 6G verification platforms are detailed for the first time. In addition, future research directions and open challenges are identified for stimulating the on-going global debate. Finally, lessons learned to date concerning 6G networks are discussed
Antenna System Design for 5G and Beyond – A Modal Approach
Antennas are one of the key components that empower a new generation of wireless technologies, such as 5G and new radar systems. It has been shown that antenna design strategies based on modal theories represent a powerful systematic approach to design practical antenna systems with high performance. In this thesis, several innovative multi-antenna systems are proposed for wireless applications in different frequency bands: from sub-6 GHz to millimeter-wave (mm-wave) bands. The thesis consists of an overview (Part I) and six scientific papers published in peer-reviewed international journals (Part II). Part I provides the overall framework of the thesis work: It presents the background and motivation for the problems at hand, the fundamental modal theories utilized to address these problems, as well as subject-specific research challenges. Brief conclusions and future outlook are also provided. The included papers of Part II can be divided into two tracks with different 5G and beyond wireless applications, both aiming for higher data rates.In the first track, Papers [I] to [IV] investigate different aspects of antenna system design for smart-phone application. Since Long Term Evolution (LTE) (so-called 3.5G) was deployed in 2009, mobile communication systems have utilized multiple-input multiple-output antenna technology (MIMO) technology to increase the spectral efficiency of the transmission channel and provide higher data rates in existing and new sub-6 GHz bands. However, MIMO requires multi-antennas at both the base stations and the user equipment (mainly smartphones) and it is very challenging to implement sub-6 GHz multi-antennas within the limited space of smartphones. This points to the need for innovative design strategies. The theory of characteristic modes (TCM) is one type of modal theory in the antenna community, which has been shown to be a versatile tool to analyze the inherent resonance properties of an arbitrarily shaped radiating structure. Characteristic modes (CMs) have the useful property of their fields being orthogonal over both the source region and the sphere at infinity. This property makes TCM uniquely suited for electrically compact MIMO antenna design.In the second track, Papers [V]-[VI] investigate new integrated antenna arrays and subarrays for the two wireless applications, which are both implemented in a higher part of the mm-wave frequency range (i.e. E-band). Furthermore, a newly developed high resolution multi-layer “Any-Layer” PCB technology is investigated to realize antenna-in-package solutions for these mmwave antenna system designs. High gain and high efficiency antennas are essential for high-speed wireless point-to-point communication systems. To meet these requirements, Paper [V] proposes directive multilayer substrate integrated waveguide (SIW) cavity-backed slot antenna array and subarray. As a background, the microwave community has already shown the benefits of modal theory in the design and analysis of closed structures like waveguides and cavities. Higher-order cavity modes are used in the antenna array design process to facilitate lower loss, simpler feeding network, and lower sensitivity to fabrication errors, which are favorable for E-band communication systems. However, waveguide/cavity modes are confined to fields within the guided media and can only help to design special types of antennas that contain those structures. As an example of the versatility of TCM, Paper [VI] shows that apart from smartphone antenna designs proposed in Papers [I]-[IV], TCM can alsobe used to find the desirable modes of the linear antenna arrays. Furthermore, apart from E-band communications, the proposed series-fed patch array topology in Paper [VI] is a good candidate for application in 79 GHz MIMO automotive radar due to its low cost, compact size, ability to suppress surface waves, as well as relatively wide impedance and flat-gain bandwidths
Direct communication radio Iinterface for new radio multicasting and cooperative positioning
Cotutela: Universidad de defensa UNIVERSITA’ MEDITERRANEA DI REGGIO CALABRIARecently, the popularity of Millimeter Wave (mmWave) wireless networks has increased due to their capability to cope with the escalation of mobile data demands caused by the unprecedented proliferation of smart devices in the fifth-generation (5G). Extremely high frequency or mmWave band is a fundamental pillar in the provision of the expected gigabit data rates. Hence, according to both academic and industrial communities, mmWave technology, e.g., 5G New Radio (NR) and WiGig (60 GHz), is considered as one of the main components of 5G and beyond networks. Particularly, the 3rd Generation Partnership Project (3GPP) provides for the use of licensed mmWave sub-bands for the 5G mmWave cellular networks, whereas IEEE actively explores the unlicensed band at 60 GHz for the next-generation wireless local area networks. In this regard, mmWave has been envisaged as a new technology
layout for real-time heavy-traffic and wearable applications.
This very work is devoted to solving the problem of mmWave band communication system while enhancing its advantages through utilizing the direct communication radio interface for NR multicasting, cooperative positioning, and mission-critical applications. The main contributions presented in this work include: (i) a set of mathematical frameworks and simulation tools to characterize multicast traffic delivery in mmWave directional systems; (ii) sidelink
relaying concept exploitation to deal with the channel condition deterioration of dynamic multicast systems and to ensure mission-critical and ultra-reliable low-latency communications; (iii) cooperative positioning techniques analysis for enhancing cellular positioning accuracy for 5G+ emerging applications that require not only improved communication characteristics but also precise localization.
Our study indicates the need for additional mechanisms/research that can be utilized: (i) to further improve multicasting performance in 5G/6G systems; (ii) to investigate sideline aspects, including, but not limited to, standardization perspective and the next relay selection strategies; and (iii) to design cooperative positioning systems based on Device-to-Device (D2D) technology
Terahertz Communications and Sensing for 6G and Beyond: A Comprehensive View
The next-generation wireless technologies, commonly referred to as the sixth
generation (6G), are envisioned to support extreme communications capacity and
in particular disruption in the network sensing capabilities. The terahertz
(THz) band is one potential enabler for those due to the enormous unused
frequency bands and the high spatial resolution enabled by both short
wavelengths and bandwidths. Different from earlier surveys, this paper presents
a comprehensive treatment and technology survey on THz communications and
sensing in terms of the advantages, applications, propagation characterization,
channel modeling, measurement campaigns, antennas, transceiver devices,
beamforming, networking, the integration of communications and sensing, and
experimental testbeds. Starting from the motivation and use cases, we survey
the development and historical perspective of THz communications and sensing
with the anticipated 6G requirements. We explore the radio propagation, channel
modeling, and measurements for THz band. The transceiver requirements,
architectures, technological challenges, and approaches together with means to
compensate for the high propagation losses by appropriate antenna and
beamforming solutions. We survey also several system technologies required by
or beneficial for THz systems. The synergistic design of sensing and
communications is explored with depth. Practical trials, demonstrations, and
experiments are also summarized. The paper gives a holistic view of the current
state of the art and highlights the issues and challenges that are open for
further research towards 6G.Comment: 55 pages, 10 figures, 8 tables, submitted to IEEE Communications
Surveys & Tutorial
Decentralized Ultra-Reliable Low-Latency Communications through Concurrent Cooperative Transmission
Emerging cyber-physical systems demand for communication technologies that enable seamless interactions between humans and physical objects in a shared environment. This thesis proposes decentralized URLLC (dURLLC) as a new communication paradigm that allows the nodes in a wireless multi-hop network (WMN) to disseminate data quickly, reliably and without using a centralized infrastructure. To enable the dURLLC paradigm, this thesis explores the practical feasibility of concurrent cooperative transmission (CCT) with orthogonal frequency-division multiplexing (OFDM). CCT allows for an efficient utilization of the medium by leveraging interference instead of trying to avoid collisions. CCT-based network flooding disseminates data in a WMN through a reception-triggered low-level medium access control (MAC). OFDM provides high data rates by using a large bandwidth, resulting in a short transmission duration for a given amount of data.
This thesis explores CCT-based network flooding with the OFDM-based IEEE 802.11 Non-HT and HT physical layers (PHYs) to enable interactions with commercial devices. An analysis of CCT with the IEEE 802.11 Non-HT PHY investigates the combined effects of the phase offset (PO), the carrier frequency offset (CFO) and the time offset (TO) between concurrent transmitters, as well as the elapsed time. The analytical results of the decodability of a CCT are validated in simulations and in testbed experiments with Wireless Open Access Research Platform (WARP) v3 software-defined radios (SDRs). CCT with coherent interference (CI) is the primary approach of this thesis.
Two prototypes for CCT with CI are presented that feature mechanisms for precise synchronization in time and frequency. One prototype is based on the WARP v3 and its IEEE 802.11 reference design, whereas the other prototype is created through firmware modifications of the Asus RT-AC86U wireless router. Both prototypes are employed in testbed experiments in which two groups of nodes generate successive CCTs in a ping-pong fashion to emulate flooding processes with a very large number of hops. The nodes stay synchronized in experiments with 10 000 successive CCTs for various modulation and coding scheme (MCS) indices and MAC service data unit (MSDU) sizes. The URLLC requirement of delivering a 32-byte MSDU with a reliability of 99.999 % and with a latency of 1 ms is assessed in experiments with 1 000 000 CCTs, while the reliability is approximated by means of the frame reception rate (FRR). An FRR of at least 99.999 % is achieved at PHY data rates of up to 48 Mbit/s under line-of-sight (LOS) conditions and at PHY data rates of up to 12 Mbit/s under non-line-of-sight (NLOS) conditions on a 20 MHz wide channel, while the latency per hop is 48.2 µs and 80.2 µs, respectively. With four multiple input multiple output (MIMO) spatial streams on a 40 MHz wide channel, a LOS receiver achieves an FRR of 99.5 % at a PHY data rate of 324 Mbit/s. For CCT with incoherent interference, this thesis proposes equalization with time-variant zero-forcing (TVZF) and presents a TVZF receiver for the IEEE 802.11 Non-HT PHY, achieving an FRR of up to 92 % for CCTs from three unsyntonized commercial devices. As CCT-based network flooding allows for an implicit time synchronization of all nodes, a reception-triggered low-level MAC and a reservation-based high-level MAC may in combination support various applications and scenarios under the dURLLC paradigm
- …