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In this paper, a study oriented to Free Space Optics (FSO) is carried out, identifying its main benefits and limitations. A practical case study is also considered in the city of Loja (Ecuador) for designing FSO technology, assessing suitable sites for deployment, climatic conditions and line of sight between the selected nodes, and technical characteristics of the equipment considered. Path loss and channel geometry analyses are also performed, where the results obtained allow understanding under which atmospheric conditions an optimal link is available. The study is validated through the execution of simulations using Optisystem software by considering several study scenarios. One of the actual results identified is the transmission rate supported by FSO technology in different atmospheric conditions, exceeding 3 km, and the high bandwidth offered compared to other technologies, such as RF, that are limited by similar factors., En el presente artículo, se realiza un estudio orientado a las comunicaciones ópticas en el espacio libre (Free Space Optics - FSO), al identificar sus principales beneficios y limitaciones. Se considera también un caso de estudio práctico en la ciudad de Loja (Ecuador) para el diseño de la tecnología FSO donde se toma en cuenta sitios idóneos para el despliegue, condiciones climáticas y línea de vista entre los nodos seleccionados y características técnicas de los equipos considerados. Se realiza además un análisis de pérdidas de trayecto y geométricas de canal, en donde los resultados obtenidos permiten comprender bajo qué condiciones atmosféricas se dispone de un enlace óptimo. El estudio se valida por medio de la ejecución de simulaciones a través del software Optisystem al considerar varios escenarios de estudio. Uno de los resultados más importantes que se logra identificar, es la tasa de transmisión que soporta la tecnología FSO en diferentes condiciones atmosféricas, que supera los 3 km, además del gran ancho de banda que ofrece en comparación a otras tecnologías como RF que se ven limitadas por factores similares.

et al.;IEEE Antennas and Propagation Society (APS);IEEE Circuits and Systems Society (CAS);IEEE Communications Society (ComSoc);IEEE Electronics Packaging Society (EPS);IEEE Intelligent Transportation Systems Society (ITSS), 6th IEEE Future Networks World Forum, FNWF 2023 -- 13 November 2023 through 15 November 2023 -- 199497, The use of a large number of antenna elements, known as Massive MIMO, is seen as a key enabling technology in the 5G and Beyond wireless ecosystem. The intelligent use of a multitude of antenna elements unleashes unprecedented flexibility and control on the physical channel of the wireless medium. Through Massive MIMO and other techniques, it is envisioned that the 5G and beyond wireless system will be able to support high throughput, high reliability (low bit-error-rate (BER)), high energy efficiency, low latency, and an internet-scale number of connected devices. Massive MIMO and related technologies will be deployed in the mid-band (sub 6 GHz) for coverage, all the way to mmWave bands to support large channel bandwidths. It is envisioned that Massive MIMO will be deployed in different environments: Frequency Division Duplex (FDD), (Time Division Duplex (TDD), indoor / outdoor, small cell, macro cell, and other heterogeneous networks (HetNet) configurations. Accurate and useful channel estimation remains a challenge in the efficient adoption of Massive MIMO techniques, and different performance-complexity tradeoffs may be supported by different Massive MIMO architectures such as digital, analog, and/or digital/analog hybrid. Carrier frequency offset (CFO), which arises due to the relative motion between the transmitter and receiver, is another important topic. Recently, maximum likelihood (ML) methods of CFO estimation have been proposed, that achieve very low root mean square (RMS) estimation errors, with a large scope for parallel processing and well suited for application with turbo codes. Massive MIMO opens up a whole new dimension of parameters where the wireless applications or other network layers may control or influence the operation and performance of the physical wireless channel. To fully reap the benefits of such flexibility, the latest advances in artificial intelligence (AI) and machine learning (ML) techniques will be leveraged to monitor and optim

In this paper, a novel index modulation-based non-orthogonal multiple access (IM-NOMA) system is proposed and investigated for both perfect and imperfect channel state information (CSI) uncertainty over Nakagami-m fading channel. The proposed system has added advantages of NOMA and IM systems. NOMA supports more users by allowing all users to utilize the same resources simultaneously whereas IM boosts spectral efficiency by conveying information to the users through both constellation domain and index domain symbols. Maximum likelihood (ML) and successive interference cancellation (SIC) detectors are used at the receiver side to detect index and data symbols. The proposed system is analyzed for different values of Nakagami-m channel parameters as well as for three different CSI conditions - perfect, fixed, and MMSE-based variable CSI uncertainty. The simulation results for the bit error rate and spectral efficiency parameters show that the proposed system outperforms the existing NOMA and OMA schemes.

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wirele

Producción Científica, Adaptive equalization is crucial in mitigating distortions and compensating for frequency response variations in communication systems. It aims to enhance signal quality by adjusting the characteristics of the received signal. Particle swarm optimization (PSO) algorithms have shown promise in optimizing the tap weights of the equalizer. However, there is a need to enhance the optimization capabilities of PSO further to improve the equalization performance. This paper provides a comprehensive study of the issues and challenges of adaptive filtering by comparing different variants of PSO and analyzing the performance by combining PSO with other optimization algorithms to achieve better convergence, accuracy, and adaptability. Traditional PSO algorithms often suffer from high computational complexity and slow convergence rates, limiting their effectiveness in solving complex optimization problems. To address these limitations, this paper proposes a set of techniques aimed at reducing the complexity and accelerating the convergence of PSO.

Sub-band full duplex is a new communication scheme technology, where a single frequency band is partitioned into sub-bands for downlink (DL) and up-link(UL) transmissions, and both can take place simultaneously. The idea behind the sub-band full duplex development is to improve the throughput, and coverage and reduce the latency of the UL communication by allowing the UL reception during the DL transmission. Several integrated ways enable sub-band frequency isolation, such as antenna’s spatial isolation and signal processing techniques to mitigate interferences. The main challenge for a gNodeB, capable of a full duplex, is self-interference mitigation. A self-interference mitigation technique enables a radio transceiver to transmit and receive simultaneously on a single channel. During the design process, the Digital Front End (DFE) of the Radio Near algorithm (RNA) is considered the main part of the study (with certain limitations) as it involves the algorithms with the use of MATLAB, which are used to mitigate the distortion caused by radio hardware imperfections. Signal processing algorithms are performed on the transmitter side and receiver side of DFE. The transmitter side includes the Crest Factor Reduction (CFR) block followed by Digital Pre-Distortion (DPD) block before the Power amplifier (PA) to linearize PA output. The transmit path also includes the feedback path for DPD which is used to linearize PA. The algorithms for CFR block namely Turbo Clipping and Peak Cancelation Crest Factor Reduction (PC-CFR) were developed and compared for the performance in terms of Adjacent Channel Leakage Ratio (ACLR) and Error Vector Magnitude (EVM). The algorithm for DPD namely 2-stage frequency selective DPD is implemented along with the legacy DPD technique, and the performance was evaluated in terms of ACLR and EVM. Finally, the Self-interference cancelation (SIC) algorithm is implemented at the receiver chain side. Signal to Interference Noise Ratio (SINR) is measure, Popular Science Summary Wireless communication is a way to transfer information from a sender to a receiver, without any wire or fiber, in the form of electromagnetic waves. The information can be sound, text data, images, etc. The radio spectrum is part of the electromagnetic spectrum with frequencies from 1 Hz to 3,000 GHz and is used in modern telecommunication. Cellular communication is one of these wireless radio technologies that has changed modern society. Users are no longer limited to text messages or voice calls. The use of social media, live video streaming, online gaming, shopping, etc are now in trend which results in the consumption of more and more data. According to the Ericsson Mobility Report Nov. 2022, the average data consumption per smartphone is expected to exceed 19 GB per month in 2023, while only new generation mobile subscriptions will hit 5 billion alone in 2028. To fulfil this demand, new technologies are required, along with the improvement of existing ones. The evolution of wireless communication is based on providing a better-quality experience and more reliable transmission with the fastest possible speed. With every 10 years passing there is a new generation of communications known as generation G-terminology. This journey of evolution started in 1981 as 1G, and now since 2020, we are in the era of 5G. The next generation is now in the research phase and is expected to be launched in the 2030s. Growing from 5G to 6G with the aim of learning from live 5G networks will play a key role in the standardization and development of 6G. Modern communication systems send and receive simultaneously to exchange information, this concept of two-way transmission is called full duplex. Frequency division duplex (FDD) and time division duplex (TDD) are two fundamental concepts for full-duplex communication. In FDD, separate frequency bands are used for uplink (phone to the network) and downlink (network to the phone) while in TDD, the same frequency

Visible light communication (VLC) system is a promising wireless communication that does not interfere with radio waves. However, it performs different performances in daytime and nighttime due to light as its resource. This research investigates a VLC system using the NRZ-OOK technique by considering external light based on BER measurement. At 10 cm and 100 bps, the bright and low light BER values system are 0.3302 and 0.2504, respectively. Meanwhile, at data rates of 1 kbps and 100 kbps, the BER values are 0.2429 and 0.4387, respectively. This result can become a basis for performance optimization in the future.

We study scintillation and bit error rate performance of mirrored Bessel beams through turbulent atmosphere in this article. We beneft from numerical method to model the atmosphere. Since scintillation plays a vital role in optical wireless applications, reduction in this term provides better performance in these systems. Related with this, our results indicate that it is possible to decrease scintillation by increasing beam order to three when strong turbulent conditions are satisfed. In addition, we observe that argument of Bessel beam has more dominant role than beam order in moderate turbulence. Lastly, mirroring brings us a slight advantage in case of bit error rate. Results of this study can be benefcial for optical link designers

We study scintillation and bit error rate performance of mirrored Bessel beams through turbulent atmosphere in this article. We beneft from numerical method to model the atmosphere. Since scintillation plays a vital role in optical wireless applications, reduction in this term provides better performance in these systems. Related with this, our results indicate that it is possible to decrease scintillation by increasing beam order to three when strong turbulent conditions are satisfed. In addition, we observe that argument of Bessel beam has more dominant role than beam order in moderate turbulence. Lastly, mirroring brings us a slight advantage in case of bit error rate. Results of this study can be benefcial for optical link designers

The enormous traffic growth sets a stringent requirement to upgrade short-reach optical links to 1.6 TbE capacity in an economically viable way. The power consumption and latency in these links should be as low as possible, especially for high-speed computing. This is possible to achieve using high baudrate on-off keying links thanks to a better noise tolerance and a relaxed requirement on linearity for electronics and photonics. In this regard, we demonstrate a 200 Gbaud on-off keying link without any optical amplification using an externally modulated laser with 3.3 dBm of modulated output power operating at 1541.25 nm wavelength. We achieve transmission over 200 meters of single-mode fiber with performance below 6.25% overhead hard-decision forward error correction threshold for each baudrate and all selection of modulation formats. We also show 108 Gbaud on-off keying link with superior performance without decision feedback equalizer up to 400 meters of single-mode fiber. In addition, we benchmark the short-reach optical link with 112 Gbaud four-level pulse amplitude modulation and 100 Gbaud six-level pulse amplitude modulation. For 108 Gbaud on-off keying and 112 Gbaud four-level pulse amplitude modulation, we can achieve an even lower bit error rate., QC 20230613

The current focus on the Internet of Things (IoT) has led to the emergence of many network scenarios with unlimited use cases, including smart homes, smart cities, smart agriculture, and more. Unmanned aerial vehicles (UAVs), also known as drones, have become increasingly popular due to their versatility and ability to collect and transmit data through various sensors and cameras. With real-time data transmission, autonomy, and cost-effectiveness, UAVs have become valuable tools for different applications, including disaster management, agriculture monitoring, and remote area control. Low-power wide-area network (LPWAN) technology plays a crucial role in enabling IoT, and LoRaWAN is one of the specific LPWAN communication technologies that can provide low power consumption and coverage over a wide range. During a catastrophe, wireless communication is critical for analyzing damaged regions, coordinating rescue and relief team actions, saving lives, and reducing economic losses. UAVs can partially replace damaged or overloaded wireless networks as an alternative wireless network provider. This thesis aimed to simulate a LoRa network and investigate the relationship between the UAV coverage radius and elevation angle, as well as the effect of multipath distortion and signal attenuation on UAV and user distance. By calculating signal-to-noise ratio (SNR) and bit error rate (BER) for LoRa in a line-of-sight (LoS) and non-line-of-sight (NLoS) environment, we provided a comprehensive analysis of LoRaWAN performance in real-life environments for long distances. The results indicate that LoRaWAN communication is reliable in various environments, making it a promising technology for emergency and medical communications., Det nuvarande fokuset på Internet of Things (IoT) har lett till uppkomsten av många nätverksscenarier med obegränsade användningsfall, inklusive smarta hem, smarta städer, smart jordbruk och mer. Obemannade flygfarkoster (UAV), även kända som drönare, har blivit allt populärare på grund av deras mångsidighet och förmåga att samla in och överföra data genom olika sensorer och kameror. Med realtidsdataöverföring, autonomi och kostnadseffektivitet har UAVs blivit värdefulla verktyg för olika applikationer, inklusive katastrofhantering, jordbruksövervakning och fjärrkontroll av områden. Low-power wide-area network (LPWAN)-teknik spelar en avgörande roll för att möjliggöra IoT, och LoRaWAN är en av de specifika LPWAN-kommunikationsteknikerna som kan ge låg strömförbrukning och täckning över ett brett spektrum. Under en katastrof är trådlös kommunikation avgörande för att analysera skadade regioner, koordinera räddnings- och hjälpteams åtgärder, rädda liv och minska ekonomiska förluster. UAV:er kan delvis ersätta skadade eller överbelastade trådlösa nätverk som en alternativ leverantör av trådlöst nätverk. Detta examensarbete syftade till att simulera ett LoRa-nätverk och undersöka sambandet mellan UAV-täckningsradien och höjdvinkeln, såväl som effekten av flervägsdistorsion och signaldämpning på UAV och användaravstånd. Genom att beräkna signal-brusförhållande (SNR) och bitfelsfrekvens (BER) för LoRa i en siktlinje (LoS) och icke-siktlinje (NLoS) miljö, gav vi en omfattande analys av LoRaWAN prestanda i verkliga miljöer för långa avstånd. Resultaten indikerar att LoRaWAN-kommunikation är tillförlitlig i olika miljöer, vilket gör den till en lovande teknik för akut- och medicinsk kommunikation.

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wirele

One of the most important units of Low-Density Parity-Check (LDPC) decoders is the Check-Node Unit. Its main task is to find the first two minimum values among incoming variable-to-check messages and return check-to-variable messages. This block significantly affects the decoding performance, as well as the hardware implementation complexity. In this paper, we first propose a modification to the check-node update rule by introducing two optimal offset factors applied to the check-to-variable messages. Then, we present the Check-Node Unit hardware architecture which performs the proposed algorithm. The main objective of this work aims to improve further the decoding performance for 5th Generation (5G) LDPC codes. The simulation results show that the proposed algorithm achieves essential improvements in terms of error correction performance. More precisely, the error-floor does not appear within Bit-Error-Rate (BER) of 10^(-8), while the decoding gain increases up to 0.21 dB compared to the baseline Normalized Min-Sum, as well as several state-of-the-art LDPC-based Min-Sum decoders.

In this paper, a novel index modulation-based non-orthogonal multiple access (IM-NOMA) system is proposed and investigated for both perfect and imperfect channel state information (CSI) uncertainty over Nakagami-m fading channel. The proposed system has added advantages of NOMA and IM systems. NOMA supports more users by allowing all users to utilize the same resources simultaneously whereas IM boosts spectral efficiency by conveying information to the users through both constellation domain and index domain symbols. Maximum likelihood (ML) and successive interference cancellation (SIC) detectors are used at the receiver side to detect index and data symbols. The proposed system is analyzed for different values of Nakagami-m channel parameters as well as for three different CSI conditions - perfect, fixed, and MMSE-based variable CSI uncertainty. The simulation results for the bit error rate and spectral efficiency parameters show that the proposed system outperforms the existing NOMA and OMA schemes.

One of the most important units of Low-Density Parity-Check (LDPC) decoders is the Check-Node Unit. Its main task is to find the first two minimum values among incoming variable-to-check messages and return check-to-variable messages. This block significantly affects the decoding performance, as well as the hardware implementation complexity. In this paper, we first propose a modification to the check-node update rule by introducing two optimal offset factors applied to the check-to-variable messages. Then, we present the Check-Node Unit hardware architecture which performs the proposed algorithm. The main objective of this work aims to improve further the decoding performance for 5th Generation (5G) LDPC codes. The simulation results show that the proposed algorithm achieves essential improvements in terms of error correction performance. More precisely, the error-floor does not appear within Bit-Error-Rate (BER) of 10^(-8), while the decoding gain increases up to 0.21 dB compared to the baseline Normalized Min-Sum, as well as several state-of-the-art LDPC-based Min-Sum decoders.

In this paper, a novel index modulation-based non-orthogonal multiple access (IM-NOMA) system is proposed and investigated for both perfect and imperfect channel state information (CSI) uncertainty over Nakagami-m fading channel. The proposed system has added advantages of NOMA and IM systems. NOMA supports more users by allowing all users to utilize the same resources simultaneously whereas IM boosts spectral efficiency by conveying information to the users through both constellation domain and index domain symbols. Maximum likelihood (ML) and successive interference cancellation (SIC) detectors are used at the receiver side to detect index and data symbols. The proposed system is analyzed for different values of Nakagami-m channel parameters as well as for three different CSI conditions - perfect, fixed, and MMSE-based variable CSI uncertainty. The simulation results for the bit error rate and spectral efficiency parameters show that the proposed system outperforms the existing NOMA and OMA schemes.

Visible light communication (VLC) system is a promising wireless communication that does not interfere with radio waves. However, it performs different performances in daytime and nighttime due to light as its resource. This research investigates a VLC system using the NRZ-OOK technique by considering external light based on BER measurement. At 10 cm and 100 bps, the bright and low light BER values system are 0.3302 and 0.2504, respectively. Meanwhile, at data rates of 1 kbps and 100 kbps, the BER values are 0.2429 and 0.4387, respectively. This result can become a basis for performance optimization in the future.

In this paper, a novel index modulation-based non-orthogonal multiple access (IM-NOMA) system is proposed and investigated for both perfect and imperfect channel state information (CSI) uncertainty over Nakagami-m fading channel. The proposed system has added advantages of NOMA and IM systems. NOMA supports more users by allowing all users to utilize the same resources simultaneously whereas IM boosts spectral efficiency by conveying information to the users through both constellation domain and index domain symbols. Maximum likelihood (ML) and successive interference cancellation (SIC) detectors are used at the receiver side to detect index and data symbols. The proposed system is analyzed for different values of Nakagami-m channel parameters as well as for three different CSI conditions - perfect, fixed, and MMSE-based variable CSI uncertainty. The simulation results for the bit error rate and spectral efficiency parameters show that the proposed system outperforms the existing NOMA and OMA schemes.

One of the most important units of Low-Density Parity-Check (LDPC) decoders is the Check-Node Unit. Its main task is to find the first two minimum values among incoming variable-to-check messages and return check-to-variable messages. This block significantly affects the decoding performance, as well as the hardware implementation complexity. In this paper, we first propose a modification to the check-node update rule by introducing two optimal offset factors applied to the check-to-variable messages. Then, we present the Check-Node Unit hardware architecture which performs the proposed algorithm. The main objective of this work aims to improve further the decoding performance for 5th Generation (5G) LDPC codes. The simulation results show that the proposed algorithm achieves essential improvements in terms of error correction performance. More precisely, the error-floor does not appear within Bit-Error-Rate (BER) of 10^(-8), while the decoding gain increases up to 0.21 dB compared to the baseline Normalized Min-Sum, as well as several state-of-the-art LDPC-based Min-Sum decoders.

A high-speed modulator on silicon nitride is demonstrated using 2 mm-long micro-transfer printed lithium niobate coupons. This device has a 3-dB bandwidth ANDgt;50GHz, and an insertion loss of 3.3 dB that allowed us to transmit 70 Gb/s., info:eu-repo/semantics/published

Phase-coded frequency modulated continuous wave (PC-FMCW) radars for joint sensing and communication are considered. The sensing and communication performance of the two signal processing methods, phase lag compensated group delay filter and filter bank receivers, are compared. It is demonstrated that the phase lag compensated group delay receiver provides better sensing performance and requires less computational complexity than the filter bank receiver. The application of the former receiver is, however, limited by the bit error rate degradation with the communication signal bandwidth., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Microwave Sensing, Signals & Systems

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wirele

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wirele

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wirele

This thesis presents a comprehensive investigation into improving wireless transmission rates and reliability through the implementation of Space Time Trellis Codes(STTC). The study focuses on enhancing the coding gain, diversity gain, and flexible transmission capabilities, which are crucial for Error-Correcting Codes (ECC)in wireless communications. Spectral efficiency, a primary concern, is achieved byincorporating Multiple-Input Multiple-Output (MIMO) techniques. This thesis discusses the encoding method and decoding algorithm for STTC systems. Then, the performance of MIMO using the Alamouti scheme is determined.Further, the benefits of Cognitive Radio (CR), an intelligent radio technology capable of automatically detecting the best available wireless channel in the spectrumat any given time, are utilized. Energy Detection (ED) is employed for SpectrumSensing (SS) to detect the presence of Primary Users (PUs). The thesis analyzes theperformance of Probability of Detection (PD) and Probability of False Alarm (PFA). Furthermore, the thesis evaluates the Bit Error Rate (BER) performance of STTCover an additive white Gaussian noise (AWGN) channel, considering different modulation schemes generated in MATLAB. Specifically, it investigates the performance ofSTTC-MIMO in terms of BER over Rayleigh channels with Quadrature AmplitudeModulation (QAM) for different combinations of transmitting and receiving antennas. The findings from this research contribute to advancing wireless communicationsystems by addressing the challenges of error correction, spectral efficiency, and reliable data transmission. The integration of STTC with MIMO and CR presents aprogressive approach towards maximizing the potential of wireless communicationtechnologies to cater to the increasing demands for seamless connectivity and superior performance. This research adds to the ongoing efforts of enhancing wirelesscommunication systems’ performance and efficiency, fostering advancements in wirele

The current focus on the Internet of Things (IoT) has led to the emergence of many network scenarios with unlimited use cases, including smart homes, smart cities, smart agriculture, and more. Unmanned aerial vehicles (UAVs), also known as drones, have become increasingly popular due to their versatility and ability to collect and transmit data through various sensors and cameras. With real-time data transmission, autonomy, and cost-effectiveness, UAVs have become valuable tools for different applications, including disaster management, agriculture monitoring, and remote area control. Low-power wide-area network (LPWAN) technology plays a crucial role in enabling IoT, and LoRaWAN is one of the specific LPWAN communication technologies that can provide low power consumption and coverage over a wide range. During a catastrophe, wireless communication is critical for analyzing damaged regions, coordinating rescue and relief team actions, saving lives, and reducing economic losses. UAVs can partially replace damaged or overloaded wireless networks as an alternative wireless network provider. This thesis aimed to simulate a LoRa network and investigate the relationship between the UAV coverage radius and elevation angle, as well as the effect of multipath distortion and signal attenuation on UAV and user distance. By calculating signal-to-noise ratio (SNR) and bit error rate (BER) for LoRa in a line-of-sight (LoS) and non-line-of-sight (NLoS) environment, we provided a comprehensive analysis of LoRaWAN performance in real-life environments for long distances. The results indicate that LoRaWAN communication is reliable in various environments, making it a promising technology for emergency and medical communications., Det nuvarande fokuset på Internet of Things (IoT) har lett till uppkomsten av många nätverksscenarier med obegränsade användningsfall, inklusive smarta hem, smarta städer, smart jordbruk och mer. Obemannade flygfarkoster (UAV), även kända som drönare, har blivit allt populärare på grund av deras mångsidighet och förmåga att samla in och överföra data genom olika sensorer och kameror. Med realtidsdataöverföring, autonomi och kostnadseffektivitet har UAVs blivit värdefulla verktyg för olika applikationer, inklusive katastrofhantering, jordbruksövervakning och fjärrkontroll av områden. Low-power wide-area network (LPWAN)-teknik spelar en avgörande roll för att möjliggöra IoT, och LoRaWAN är en av de specifika LPWAN-kommunikationsteknikerna som kan ge låg strömförbrukning och täckning över ett brett spektrum. Under en katastrof är trådlös kommunikation avgörande för att analysera skadade regioner, koordinera räddnings- och hjälpteams åtgärder, rädda liv och minska ekonomiska förluster. UAV:er kan delvis ersätta skadade eller överbelastade trådlösa nätverk som en alternativ leverantör av trådlöst nätverk. Detta examensarbete syftade till att simulera ett LoRa-nätverk och undersöka sambandet mellan UAV-täckningsradien och höjdvinkeln, såväl som effekten av flervägsdistorsion och signaldämpning på UAV och användaravstånd. Genom att beräkna signal-brusförhållande (SNR) och bitfelsfrekvens (BER) för LoRa i en siktlinje (LoS) och icke-siktlinje (NLoS) miljö, gav vi en omfattande analys av LoRaWAN prestanda i verkliga miljöer för långa avstånd. Resultaten indikerar att LoRaWAN-kommunikation är tillförlitlig i olika miljöer, vilket gör den till en lovande teknik för akut- och medicinsk kommunikation.

In this paper, we present a class of integer codes capable of correcting burst asymmetric errors. The presented codes are constructed with the help of a computer and have the potential to be used in various practical systems, such as optical networks and VLSI memories. In order to evaluate the performance of the proposed codes, the paper analyzes the probability of erroneous decoding for different bit error rates. The presented codes are also analyzed from a rate-efficiency point of view. The obtained results show that for many data lengths they require less check-bits than optimal burst error correcting codes.

Depression detection from social media texts such as Tweets or Facebook comments could be very beneficial as early detection of depression may even avoid extreme consequences of long-term depression i.e. suicide. In this study, depression intensity classification is performed using a labeled Twitter dataset. Further, this study makes a detailed performance evaluation of four transformer-based pre-trained small language models, particularly those having less than 15 million tunable parameters i.e. Electra Small Generator (ESG), Electra Small Discriminator (ESD), XtremeDistil-L6 (XDL) and Albert Base V2 (ABV) for classification of depression intensity using Tweets. The models are fine-tuned to get the best performance by applying different hyperparameters. The models are tested by classification of depression intensity of labeled tweets for three label classes i.e. ‘severe’, ‘moderate’, and ‘mild’ by downstream fine-tuning the parameters. Evaluation metrics such as accuracy, F1, precision, recall, and specificity are calculated to evaluate the performance of the models. Comparative analysis of these models is also done with a moderately larger model i.e. DistilBert which has 67 million tunable parameters for the same task with the same experimental settings. Results indicate that ESG outperforms all other models including DistilBert due to its better deep contextualized text representation as it gets the best F1 score of 89% with comparatively less training time. Further optimization of ESG is also proposed to make it suitable for low-powered devices. This study helps to achieve better classification performance of depression detection as well as to choose the best language model in terms of performance and less training time for Twitter-related downstream NLP tasks., This work was supported in part by the Department of Informatics, University of Valladolid, Spain; in part by the Spanish Ministry of Economy and Competitiveness through Feder Funds under Grant TEC2017-84321-C4-2-R; in part by MINECO/AEI/ERDF (EU) under Grant PID2019-105660RB-C21 / AEI / 10.13039/501100011033; in part by the Aragón Government under Grant T58_20R research group; and in part by the Construyendo Europa desde Aragón under Grant ERDF 2014-2020

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low, open access, Riktad luftdatalänk

For NAND flash memory, designing a good low-density parity-check (LDPC) decoding algorithm could ensure data reliability. When the decoding algorithm is implemented in hardware, it is necessary to achieve attractive trade off between implementation complexity and decoding performance. In this paper, a novel low bit-width decoding scheme is introduced. In this scheme, the Quasi-Cyclic LDPC (QC-LDPC) is used, and the row-layered normalized min-sum algorithm is improved by restricting the amplitude of minimum and second-minimum values in each check node (CN) updating. The simulation shows that our approach achieves a lower UBER (Uncorrectable Bit Error Rate) with a negligible increase in computational complexity, especially with low precision input log-likelihood ratio (LLR)., QC 20220613

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low, open access, Riktad luftdatalänk

application/pdf, ICC 2022 - IEEE International Conference on Communications. 2022, ICC 2022 - IEEE International Conference on Communications, Seoul, Korea, Republic of, 16-20 May 2022, IEEE

application/pdf, ICC 2022 - IEEE International Conference on Communications. 2022, ICC 2022 - IEEE International Conference on Communications, Seoul, Korea, Republic of, 16-20 May 2022, IEEE

2022 International Balkan Conference on Communications and Networking, BalkanCom 2022 -- 22 August 2022 through 24 August 2022 -- 183326, This paper evaluates the effect of end-to-end delay on lifetime and the average bit error rate for wireless sensor networks where each sensor node sends its data to sink via directional antennas. Using Mixed Integer Programming, lifetime is optimized for circular network topologies with different numbers of nodes. Using both directional and omnidirectional antennas, different end-to-end delay restrictions are applied to the same sensor network to examine the effect on lifetime and average bit error rate. When delay restriction is relaxed, an increase in lifetime and a decrease in average bit error rate are observed for both antennas. In this case, the directional antenna benefits more from relaxing the delay restriction. In the end, an optimal end-to-end delay was determined which provides sufficient lifetime and bit error rate while taking into account data freshness. © 2022 IEEE.

2022 International Balkan Conference on Communications and Networking, BalkanCom 2022 -- 22 August 2022 through 24 August 2022 -- 183326, This paper evaluates the effect of end-to-end delay on lifetime and the average bit error rate for wireless sensor networks where each sensor node sends its data to sink via directional antennas. Using Mixed Integer Programming, lifetime is optimized for circular network topologies with different numbers of nodes. Using both directional and omnidirectional antennas, different end-to-end delay restrictions are applied to the same sensor network to examine the effect on lifetime and average bit error rate. When delay restriction is relaxed, an increase in lifetime and a decrease in average bit error rate are observed for both antennas. In this case, the directional antenna benefits more from relaxing the delay restriction. In the end, an optimal end-to-end delay was determined which provides sufficient lifetime and bit error rate while taking into account data freshness. © 2022 IEEE.

The massive amount of misinformation spreading on the internet on a daily basis has enormous negative impacts on societies. Therefore, we need systems to help fact-checkers to combat misinformation and to raise public awareness of this important problem. In this article, we propose a hybrid model which combines bidirectional encoder representations from transformer (BERT) model with various features to prioritize claims based on their check-worthiness. Features we use include domain-specific controversial topics (CT), word embeddings (WE), part-of-speech (POS) tags, and others. In addition, we explore various ways of increasing labeled data size to effectively train the models, such as increasing positive (IncPos) samples, active learning (AL), and utilizing labeled data in other languages. In our extensive experiments, we show that our model outperforms all state-of-the-art models in test collections of Conference and Labs of Evaluation Forum (CLEF) CheckThat! Lab (CTL) 2018 and 2019. In addition, when positive samples are increased in the training set, our model achieves the best mean average precision (MAP) score reported so far for the test collection of CTL 2020. Furthermore, we show that cross-lingual training is effective for prioritizing Arabic and Turkish claims, but not for English.

In this paper, we consider airborne communication networks with directed air data links between high-mobility airborne platforms. Orthogonal time frequency space (OTFS) modulation is used to overcome the effects of the high Doppler shifts induced by the high relative speeds among airborne platforms which can be in excess of 1200 m/s. The performance of the considered system is assessed using the Rician channel to model the directed air data links accounting for the ratio of the signal power in the line-of-sight path to the signal power in the scattered paths. The numerical results reveal significant bit error rate (BER) improvements with increased Rician K-factor, illustrate the trade-offs between BER and bits per symbol offered by different modulation schemes, and show the independence of the BER from the relative speeds among airborne platforms. Further, it is shown that the BER of a single path directed air data link approaches that of a two-ray channel for a sufficiently large Rician K-factor. © 2022 IEEE., Riktad luftdatalänk

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., Advances in emerging resistive random-access memory (ReRAM) technology show promise for its use in future computing systems, enabling neuromorphic and memory-centric computing architectures. However, one aspect that holds back the widespread practical use of ReRAM is the behavioral variability of resistive switching devices. In this context, a radically new path towards ReRAM-based electronics concerns the exploitation of noise and the Stochastic Resonance (SR) phenomenon as a mechanism to mitigate the impact of variability. While SR has been already demonstrated in ReRAM devices and its potential impact has been analyzed for memory applications, related works have only focused on voltage input signals. In this work we present preliminary results concerning the exploration of SR in current-driven ReRAM devices, commercially available by Knowm Inc. Our results indicate that additive noise of amplitude s = 0.125uA can stabilize the cycling performance of the devices, whereas higher noise amplitude improves the HRS-LRS resistance window, thus could affect positively the Bit Error Rate (BER) metric in ReRAM memory applications., Supported by the Chilean research grants FONDECYT INICIACION 11180706 and ANID-Basal FB0008, and by the Spanish MCIN grants PID2019-105658RB-I00, and MCIN/AEI/10.13039/501100011033 grant PID2019-103869RB-C33., Peer Reviewed, Postprint (author's final draft)

The energy efficiency of an Internet-of-Things (IoT) receiver can be improved by introducing an adjustable trade-off between signal-quality and energy consumption. In good channel conditions, the receiver can be set to consume less energy per bit, without compromising signal quality in bad channel conditions. We propose a system-level receiver design that enables adequate configuration and combination of signal-quality and energy trade-offs in multiple receiver components. Co-design of all components is essential. We identify the most energy-efficient configurations in our system-level design under different channel conditions. With those configurations, the proposed receiver outperforms a state-of-the-art adjustable receiver with only an adjustable analog front end by several tens of percent in energy per successfully received bit and by 2x in energy-sensitivity configuration range. To show the efficacy of the proposed approach, we integrate a model of the proposed design into the OMNeT++ simulator and show the benefits on an environmental monitoring scenario. In this scenario, we report up to 6x energy savings for the entire transceiver compared to the conventional transceiver design without adjustable receiver.

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low, open access, Riktad luftdatalänk

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low, open access, Riktad luftdatalänk

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low, open access, Riktad luftdatalänk

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low, open access, Riktad luftdatalänk

This paper investigates a symbiotic unmanned aerial vehicle (UAV)-assisted intelligent reflecting surface (IRS) radio system, where the UAV is leveraged to help the IRS reflect its own signals to the base station, and meanwhile enhance the UAV transmission by passive beamforming at the IRS. First, we consider the weighted sum bit error rate (BER) minimization problem among all IRSs by jointly optimizing the UAV trajectory, IRS phase shift matrix, and IRS scheduling, subject to the minimum primary rate requirements. To tackle this complicated problem, a relaxation-based algorithm is proposed. We prove that the converged relaxation scheduling variables are binary, which means that no reconstruct strategy is needed, and thus the UAV rate constraints are automatically satisfied. Second, we consider the fairness BER optimization problem. We find that the relaxation-based method cannot solve this fairness BER problem since the minimum primary rate requirements may not be satisfied by the binary reconstruction operation. To address this issue, we first transform the binary constraints into a series of equivalent equality constraints. Then, a penalty-based algorithm is proposed to obtain a suboptimal solution. Numerical results are provided to evaluate the performance of the proposed designs under different setups, as compared with benchmarks.

When people debate, they want to familiarize themselves with a whole range of arguments about a given topic in order to deepen their knowledge and inspire new claims. However, the amount of differently phrased arguments is humongous, making the process of processing them time-consuming. In spite of many works on using arguments (e.g. counter-argument generation), there is only a few studies on argument aggregation. To address this problem, we propose a new task in argument mining - Argument Extraction, which gathers similar arguments into key points, usually single sentences describing a set of arguments for a given debate topic. Such a short summary of related arguments has been manually created in previous research, while in our research key point generation becomes fully automatic, saving time and cost. As the first step of key point generation we explore existing similarity calculation methods, i.e. Sentence-BERT and MoverScore to investigate their performance. Next, we propose a combination of argument similarity and Maximal Marginal Relevance (MMR) for extracting key phrases to be utilized in our novel task of Argument Extraction. Experimental results show that MoverScore-based MMR outperforms strong baselines covering 72.5% of arguments when eleven or more arguments are extracted. This percentage is almost identical with the cover rate of human-made key points.

The success of the Internet-of-Things (IoT) paradigm relies on, among other things, developing energy-efficient communication techniques that can enable information exchange among billions of battery-operated IoT devices. With its technological capability of simultaneous information and energy transfer, ambient backscatter is quickly emerging as an appealing solution for this communication paradigm, especially for the links with low data rate requirements. However, many challenges and limitations of ambient backscatter have to be overcome for widespread adoption of the technology in future wireless networks. Motivated by this, we study the design and implementation of ambient backscatter systems, including non-coherent detection and encoding schemes, and investigate techniques such as multiple antenna interference cancellation and frequency-shift backscatter to improve the bit error rate performance of the designed ambient backscatter systems. First, the problem of coherent and semi-coherent ambient backscatter is investigated by evaluating the exact bit error rate (BER) of the system. The test statistic used for the signal detection is based on the averaging of energy of the received signal samples. It is important to highlight that the conditional distributions of this test statistic are derived using the central limit theorem (CLT) approximation in the literature. The characterization of the exact conditional distributions of the test statistic as non-central chi-squared random variable for the binary hypothesis testing problem is first handled in our study, which is a key contribution of this particular work. The evaluation of the maximum likelihood (ML) detection threshold is also explored which is found to be intractable. To overcome this, alternate strategies to approximate the ML threshold are proposed. In addition, several insights for system design and implementation are provided both from analytical and numerical standpoints. Second, the highly appealing

Altres ajuts: Universitat Autònoma de Barcelona, Directional modulation (DM) has been proposed as a technique to enhance physical layer security of wireless transmissions. In DM, the improvement of security is achieved by increasing the transmitted power in such a way that the bit error rate (BER) is degraded in the observation angles out of the desired secure direction. The performance of DM in terms of BER is typically evaluated by transmitting a stream of symbols for every observation angle, but this approach can be time consuming. In this communication, we propose an approach to evaluate, accurately and efficiently, the BER of dynamic DM (DDM) for standard modulation schemes. Several DDM configurations will be tested to illustrate the benefits and limitations of the evaluation method. The proposed approach is also used to present a non-iterative DDM synthesis with restrictions in the BER response.

Offset spatial modulation (OSM) is an attractive multiple-input–multiple-output (MIMO) transmission scheme, which alleviates the switching frequency limitation of the radio frequency chain in the spatial modulation technology. In this article, we investigate the bit error performance of OSM in the presence of imperfect channel estimation toward a practical transmission scenario. More specifically, with the aid of union bound technique, a general performance analysis framework of the OSM system with channel estimation errors is proposed. Based on the above analysis framework, the upper bounds of bit error rate for the static and dynamic modes of OSM are both derived, respectively. Finally, simulation results demonstrate that the analytical bounds are tight for a wide range of signal-to-noise ratio (SNR) and variable system configurations., QC 20220216

The employment of unmanned aerial vehicles is currently a fact in modern warfare. The benefit of using drones as a swarm, working together to accomplish a task, will help save lives; however, the communication among drones within a swarm is a challenge with the available technology due mainly to the power requirements to operate in a small device. Inspired by the massive machine-type communication 5th generation mobile networks, this work offers a novel method of identification and ranging for drones in swarm. The 5G communication channel's preamble with a Zadoff-Chu (ZC) sequence is expected to provide low power and less interference between devices and yet yield good mean-square error results when a matched filter is applied. Simulations considering different numbers of drones within a swarm embedded in noisy and Doppler-affected environments demonstrate promising results even in poor scenarios with small signal-to-noise ratio and high Doppler frequency shift, especially when the batch of ZC sequences' root indexes are selected into a special group., Capitao-Tentente, Brazilian Navy, Approved for public release. Distribution is unlimited.