231 research outputs found

    Energy-Sustainable IoT Connectivity: Vision, Technological Enablers, Challenges, and Future Directions

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    Technology solutions must effectively balance economic growth, social equity, and environmental integrity to achieve a sustainable society. Notably, although the Internet of Things (IoT) paradigm constitutes a key sustainability enabler, critical issues such as the increasing maintenance operations, energy consumption, and manufacturing/disposal of IoT devices have long-term negative economic, societal, and environmental impacts and must be efficiently addressed. This calls for self-sustainable IoT ecosystems requiring minimal external resources and intervention, effectively utilizing renewable energy sources, and recycling materials whenever possible, thus encompassing energy sustainability. In this work, we focus on energy-sustainable IoT during the operation phase, although our discussions sometimes extend to other sustainability aspects and IoT lifecycle phases. Specifically, we provide a fresh look at energy-sustainable IoT and identify energy provision, transfer, and energy efficiency as the three main energy-related processes whose harmonious coexistence pushes toward realizing self-sustainable IoT systems. Their main related technologies, recent advances, challenges, and research directions are also discussed. Moreover, we overview relevant performance metrics to assess the energy-sustainability potential of a certain technique, technology, device, or network and list some target values for the next generation of wireless systems. Overall, this paper offers insights that are valuable for advancing sustainability goals for present and future generations.Comment: 25 figures, 12 tables, submitted to IEEE Open Journal of the Communications Societ

    LiDAR aided simulation pipeline for wireless communication in vehicular traffic scenarios

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    Abstract. Integrated Sensing and Communication (ISAC) is a modern technology under development for Sixth Generation (6G) systems. This thesis focuses on creating a simulation pipeline for dynamic vehicular traffic scenarios and a novel approach to reducing wireless communication overhead with a Light Detection and Ranging (LiDAR) based system. The simulation pipeline can be used to generate data sets for numerous problems. Additionally, the developed error model for vehicle detection algorithms can be used to identify LiDAR performance with respect to different parameters like LiDAR height, range, and laser point density. LiDAR behavior on traffic environment is provided as part of the results in this study. A periodic beam index map is developed by capturing antenna azimuth and elevation angles, which denote maximum Reference Signal Receive Power (RSRP) for a simulated receiver grid on the road and classifying areas using Support Vector Machine (SVM) algorithm to reduce the number of Synchronization Signal Blocks (SSBs) that are needed to be sent in Vehicle to Infrastructure (V2I) communication. This approach effectively reduces the wireless communication overhead in V2I communication

    Intelligent Sensing and Learning for Advanced MIMO Communication Systems

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    Seventy Years of Radar and Communications: The road from separation to integration

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    Radar and communications (R&C) as key utilities of electromagnetic (EM) waves have fundamentally shaped human society and triggered the modern information age. Although R&C had been historically progressing separately, in recent decades, they have been converging toward integration, forming integrated sensing and communication (ISAC) systems, giving rise to new highly desirable capabilities in next-generation wireless networks and future radars. To better understand the essence of ISAC, this article provides a systematic overview of the historical development of R&C from a signal processing (SP) perspective. We first interpret the duality between R&C as signals and systems, followed by an introduction of their fundamental principles. We then elaborate on the two main trends in their technological evolution, namely, the increase of frequencies and bandwidths and the expansion of antenna arrays. We then show how the intertwined narratives of R&C evolved into ISAC and discuss the resultant SP framework. Finally, we overview future research directions in this field

    Dual-Function Radar Communications via Frequency-Hopping Code Selection

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    Dual-function radar communications (DFRC) systems serve an indispensable role within emerging paradigm shifts combining sensing modalities with information exchange. Utilising an integrated waveform, the spectral and spatial degrees of freedom (DoF) of the host radar platform are exploited to embed information symbols into the radar waveform. Furthermore, DFRC systems are beginning to embed the information in the fast-time, i.e. within the radar pulse. One method involves the use of orthogonal frequency-hopping (FH) waveforms in conjunction with multiple-input multiple-output (MIMO) radar arrays. While the secondary communications function is achieved, modulating the radar fast-time comes at the expense of the primary sensing operation. In this dissertation, we study the implementation of a novel information embedding scheme for frequency-hopped MIMO (FH-MIMO) DFRC applications. We first develop a generalised framework which unifies existing FH-MIMO DFRC schemes. We then expose new methods of fast-time information embedding, such as the frequency-hopping code selection (FHCS) scheme. We also design hybrid information embedding strategies which enable significantly higher bit rates at no further expense of the radar. Then, we characterise the communications performance of the FHCS scheme exposed by this generalised framework. We identify significant aspects of FHCS signalling which relate to index modulation schemes as a whole, such as the truncation of the symbol dictionary. We formulate an optimisation relating the maximum transform-limit with the achievable communications symbol rate and bit rate. Following this, we address the issue of symbol detection as it pertains to index modulation schemes utilising truncated codebooks. We design a low-complexity communications receiver for the FHCS scheme which ensures valid membership of the estimated symbol to the allowed communications constellation. Furthermore, we derive expressions which show that the probability of symbol error reduces in those cases where truncated dictionaries are employed. Finally, we analyse the performance of the integrated FHCS waveform from the perspective of the primary radar operation. We establish a measure which enables the analysis of the average ambiguity function across all realisations of the permuted symbol dictionary. We also derive the performance of the radar receiver operating characteristics (ROC), including the false-alarm and detection probabilities

    Terahertz Communications and Sensing for 6G and Beyond: A Comprehensive View

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    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

    Future Trends in Advanced Materials and Processes

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    The Special Issue “Future Trends in Advanced Materials and Processes” contains original high-quality research papers and comprehensive reviews addressing the relevant state-of-the-art topics in the area of materials focusing on relevant or innovative applications such as radiological hazard evaluations of non-metallic materials, composite materials' characterization, geopolymers, metallic biomaterials, etc

    Waveform Design and Processing for Joint Wireless Communications and Sensing

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    Since the advent of radar/sensing systems, they have always had fixed frequencies for operation. Due to the exponential growth of communications systems, the need for dedicated spectrum for them also increased, causing spectrum scarcity for both communications and sensing. It was obvious that some form of flexible spectrum sharing was necessary between these two functionalities. Soon enough, this led the researchers to focus on joint communications and sensing (JCAS) systems that share spectral resources efficiently. The hardware convergence due to the similar functioning of the two systems complemented the frequency convergence of JCAS systems. In fact, JCAS is one of the prominent requirements in future sixth-generation (6G) communications systems. This thesis focuses on integrating the sensing functionality on top of wireless mobile communications systems, such as in fifth-generation (5G). To facilitate effective JCAS, the thesis provides signal processing techniques for designing waveforms that optimally share the spectral resources, for single-input single-output (SISO) as well as multiple-input multiple-output (MIMO) systems. In addition, novel radar processing techniques are investigated for MIMO systems to better detect the targets in the environment. The standard waveform in 5G, that is, orthogonal frequency-division multiplexing (OFDM), is also considered for joint waveform design. In such a communications system, the resources are usually not fully utilized and there exist unused subcarriers within the OFDM waveform. These subcarriers are filled with optimized samples to minimize the lower bounds of delay and velocity estimates’ error variances of sensing, for SISO JCAS systems. The simulations with standard-compliant 5G waveforms illustrate the improvements possible in sensing, while also helping to maximize the efficiency in the transmit power amplification process, along the same optimization scheme. The simulation results are complemented through practical radio-frequency measurements of an outdoor environment depicting the significant gains that can be obtained in the range–angle map of sensing, due to the waveform optimization. For MIMO JCAS systems, apart from conventional communications streams, separate transmit (TX) streams are used to improve sensing performance through two separate schemes. One scheme involves optimizing the sensing streams to minimize the lower bounds of delay and angle estimates’ error variances of sensing. Simulation results indicate that the errors of sensing can be minimized while striking a good balance with the communications capacity. The other scheme depicts that the target detection can be enhanced using sensing streams on top of a communications stream. Specifically, the number of false targets detected can be significantly reduced in comparison to single-stream communication. The antenna arrays in MIMO communications systems nowadays are a combination of analog and digital architectures, i.e., hybrid, instead of consisting of a fullydigital architecture, for reduced costs and power consumption. Radar processing in such a hybrid architecture with multiple TX streams is not straightforward in comparison to the conventional fully-digital MIMO radar. Hence, this thesis also provides novel radar processing techniques to obtain the range–angle and range–velocity maps of the sensed environment. The simulation results illustrate that the targets can be reliably detected through the proposed MIMO processing, while also providing super-resolution in the angular domain

    Joint Waveform and Clustering Design for Coordinated Multi-point DFRC Systems

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    To improve both sensing and communication performances, this paper proposes a coordinated multi-point (CoMP) transmission design for a dual-functional radar-communication (DFRC) system. In the proposed CoMP-DFRC system, the central processor (CP) coordinates multiple base stations (BSs) to transmit both the communication signal and the dedicated probing signal. The communication performance and the sensing performance are both evaluated by the signal-to-interference-plus-noise ratio (SINR). Given the limited backhaul capacity, we study the waveform and clustering design from both the radar-centric perspective and the communication-centric perspective. Dinkelbach’s transform is adopted to handle the single-ratio fractional objective for the radar-centric problem. For the communication-centric problem, we adopt quadratic transform to convexitify the multi-ratio fractional objective. Then, the rank-one constraint of communication beamforming vector is relaxed by semidefinite relaxation (SDR), and the tightness of SDR is further proved to guarantee the optimal waveform design with fixed clustering. For dynamic clustering, equivalent continuous functions are used to represent the non-continuous clustering variables. Successive convex approximation (SCA) is further utilized to convexitify the equivalent functions. Simulation results are provided to verify the effectiveness of all proposed designs
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