1,542 research outputs found
Analysis and Design of Non-Orthogonal Multiple Access (NOMA) Techniques for Next Generation Wireless Communication Systems
The current surge in wireless connectivity, anticipated to amplify significantly in future wireless technologies, brings a new wave of users. Given the impracticality of an endlessly expanding bandwidth, there’s a pressing need for communication techniques that efficiently serve this burgeoning user base with limited resources. Multiple Access (MA) techniques, notably Orthogonal Multiple Access (OMA), have long addressed bandwidth constraints. However, with escalating user numbers, OMA’s orthogonality becomes limiting for emerging wireless technologies. Non-Orthogonal Multiple Access (NOMA), employing superposition coding, serves more users within the same bandwidth as OMA by allocating different power levels to users whose signals can then be detected using the gap between them, thus offering superior spectral efficiency and massive connectivity. This thesis examines the integration of NOMA techniques with cooperative relaying, EXtrinsic Information Transfer (EXIT) chart analysis, and deep learning for enhancing 6G and beyond communication systems. The adopted methodology aims to optimize the systems’ performance, spanning from bit-error rate (BER) versus signal to noise ratio (SNR) to overall system efficiency and data rates. The primary focus of this thesis is the investigation of the integration of NOMA with cooperative relaying, EXIT chart analysis, and deep learning techniques. In the cooperative relaying context, NOMA notably improved diversity gains, thereby proving the superiority of combining NOMA with cooperative relaying over just NOMA. With EXIT chart analysis, NOMA achieved low BER at mid-range SNR as well as achieved optimal user fairness in the power allocation stage. Additionally, employing a trained neural network enhanced signal detection for NOMA in the deep learning scenario, thereby producing a simpler signal detection for NOMA which addresses NOMAs’ complex receiver problem
Optical Wireless Communications Using Intelligent Walls
This chapter is devoted to discussing the integration of intelligent
reflecting surfaces (IRSs), or intelligent walls, in optical wireless
communication (OWC) systems. IRS technology is a revolutionary concept that
enables communication systems to harness the surrounding environment to control
the propagation of light signals. Based on this, specific key performance
indicators could be achieved by altering the electromagnetic response of the
IRSs. In the following, we discuss the background theory and applications of
IRSs and present a case study for an IRS-assisted indoor light-fidelity (LiFi)
system. We then highlight some of the challenges related to this emerging
concept and elaborate on future research directions
SUTMS - Unified Threat Management Framework for Home Networks
Home networks were initially designed for web browsing and non-business critical applications. As infrastructure improved, internet broadband costs decreased, and home internet usage transferred to e-commerce and business-critical applications. Today’s home computers host personnel identifiable information and financial data and act as a bridge to corporate networks via remote access technologies like VPN. The expansion of remote work and the transition to cloud computing have broadened the attack surface for potential threats. Home networks have become the extension of critical networks and services, hackers can get access to corporate data by compromising devices attacked to broad- band routers. All these challenges depict the importance of home-based Unified Threat Management (UTM) systems. There is a need of unified threat management framework that is developed specifically for home and small networks to address emerging security challenges. In this research, the proposed Smart Unified Threat Management (SUTMS) framework serves as a comprehensive solution for implementing home network security, incorporating firewall, anti-bot, intrusion detection, and anomaly detection engines into a unified system. SUTMS is able to provide 99.99% accuracy with 56.83% memory improvements. IPS stands out as the most resource-intensive UTM service, SUTMS successfully reduces the performance overhead of IDS by integrating it with the flow detection mod- ule. The artifact employs flow analysis to identify network anomalies and categorizes encrypted traffic according to its abnormalities. SUTMS can be scaled by introducing optional functions, i.e., routing and smart logging (utilizing Apriori algorithms). The research also tackles one of the limitations identified by SUTMS through the introduction of a second artifact called Secure Centralized Management System (SCMS). SCMS is a lightweight asset management platform with built-in security intelligence that can seamlessly integrate with a cloud for real-time updates
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
Design of Reconfigurable Intelligent Surfaces for Wireless Communication: A Review
Existing literature reviews predominantly focus on the theoretical aspects of
reconfigurable intelligent surfaces (RISs), such as algorithms and models,
while neglecting a thorough examination of the associated hardware components.
To bridge this gap, this research paper presents a comprehensive overview of
the hardware structure of RISs. The paper provides a classification of RIS cell
designs and prototype systems, offering insights into the diverse
configurations and functionalities. Moreover, the study explores potential
future directions for RIS development. Notably, a novel RIS prototype design is
introduced, which integrates seamlessly with a communication system for
performance evaluation through signal gain and image formation experiments. The
results demonstrate the significant potential of RISs in enhancing
communication quality within signal blind zones and facilitating effective
radio wave imaging
Cooperative transport communication in AGV groups using Omni-Curve Parameters
El concepto de los parámetros Omni-Curva se utiliza en el contexto de los robots AGV. Permite que un grupo de vehÃculos pueda moverse como si fuera uno y, por ejemplo, transportar una carga juntos (transporte cooperativo). Su objetivo es ser universal, es decir, que sirva para cualquier AGV sin importar su configuración de chasis o número de ruedas. Para lograrlo, este concepto calcula la dirección y velocidad de cada rueda conociendo su posición relativa constante dentro del grupo y la trayectoria planeada. Para cada instante en la trayectoria, los parámetros Omni-Curva pueden tomar valores diferentes.
Este trabajo se centra en discernir cuál es la mejor forma de asegurar que los AGV poseen los valores actualizados de estos parámetros. Primero se estudian y comparan diferentes tipos de tecnologÃas de comunicación. Las caracterÃsticas más deseadas son robustez y baja latencia. Después, las más interesantes se utilizan para construir un sistema de comunicaciones capaz de enviar y recibir estos parámetros. También se desarrollan métodos para optimizar el flujo de información dentro del grupo de AGV. Finalmente, se comparan y prueban las tecnologÃas utilizadas y se exponen las conclusiones.The concept of Omni-Curve Parameters (OCPs) is used in the context of Automated Guided Vehicles (AGVs). It allows a group of vehicles to move as if they were one and, for example, carry a load together (cooperative transport). Its aim is to be universal, which means that any vehicle could use it regardless of their chassis configuration or number of wheels. To achieve this, the concept calculates the direction and speed of each wheel knowing their constant relative position in the group and the planned trajectory. For each instant of the trajectory, there can be different values for the OCPs, which are three: floating angle, nominal velocity and nominal curvature.
This work focuses on discerning how best to ensure that the AGVs update the values of the OCPs. First, some communication technologies are studied and compared. Robustness and low latency are some of the most desired features. Then, the most appealing ones are used to build a communication system capable of sending and receiving this parameters, as well as some concepts are developed to optimize the information flow of the OCPs through the group. Finally, technologies are compared
and tested and conclusions are drawn.Departamento de IngenierÃa de Sistemas y AutomáticaMáster en IngenierÃa Industria
Highly Linear Filtering TIA for 5G wireless standard and beyond
The demand for high data rates in emerging wireless standards is a result
of the growing number of wireless device subscribers. This demand is met
by increasing the channel bandwidth in accordance with historical trends. As
MIMO technology advances, more bands and antennas are expected to be used.
The most recent 5G standard makes use of mm-wave bands above 24GHz to
expand the channel bandwidth. Channel bandwidth can exceed 2GHz when
carrier aggregation is used. From the receiver’s point of view, this makes the
baseband filter’s design, which is often a TIA, more difficult. This is due to
the fact that as the bandwidth approaches the GHz range, the TIA’s UGBW
should be more than 5GHz and it should have a high loop gain up to high
frequencies. A closed-loop TIA with configurable bandwidth up to 1.5GHz
is described in this scenario. Operational Transconductance Amplifier (OTA)
closed in shunt-feedback is the foundation of the TIA. The proposed OTA is
based on FeedForward topology (FF) together with inductive peaking technique
to ensure stability rather than using the traditional Miller compensation
technique. The TIA is able to produce GLoop unity gain bandwidth of
7.5GHz and high loop gain (i.e. 27dB @ 1GHz) using this method. The mixer
and LNA’s linearity will benefit from this. Utilizing TSMC 28nm CMOS technology,
a prototype has been created using this methodology. The output
integrated noise from 20MHz to 1.5GHz is lower than 300μVrms with a power
consumption of 17mW, and the TIA achieves In-band OIP3 of 33dBm.
Additionally, a direct-conversion receiver for 5G applications is described. The
7GHz RF signal is down-converted to baseband by the receiver. Two cascaded
LNTAs based on a common-gate transformer-based design make up the frontend.
With an RF gain of 80mS and a gain variability of 31dB, it provides
wideband matching from 6GHz to 8GHz. A double-balanced passive mixer is
driven by the LNTA. The channel bandwidth from 50MHz to 2GHz is covered by two baseband paths. The first path, called as the low frequency path (LF),
covers the channel bandwidth ranging from 50MHz to 400 MHz. In contrast,
the second path, called as the high frequency path (HF), covers the channel
bandwidth between 800MHz and 2GHz. Two baseband provide gain variability
of 14dB, making the overall receiver able to have a gain configurability
from 45dB to 0dB. Out-of-band (OOB) selectivity at 4 times the band-edge
is greater than 33dB for each configurability. When the gain is at its maximum,
the noise figure is less than 5.8dB, and the slope of the noise rise as
the gain falls is less than 0.7dB/dB. The receiver guarantee an IB-OIP3 larger
than 21dBm for any gain configuration. The receiver has been implemented
in TSMC 28nm CMOS technology, consuming 51mW for LF path and 68mW
for HF path. The measurement results are in perfect accordance with the
requirements of the design
On the Effect of Channel Knowledge in Underwater Acoustic Communications: Estimation, Prediction and Protocol
Underwater acoustic communications are limited by the following channel impairments: time variability, narrow bandwidth, multipath, frequency selective fading and the Doppler effect. Orthogonal Frequency Division Modulation (OFDM) is recognized as an effective solution to such impairments, especially when optimally designed according to the propagation conditions. On the other hand, OFDM implementation requires accurate channel knowledge atboth transmitter and receiver sides. Long propagation delay may lead to outdated channel information. In this work, we present an adaptive OFDM scheme where channel state information is predicted through a Kalman-like filter so as to optimize communication parameters, including the cyclic prefix length. This mechanism aims to mitigate the variability of channel delay spread. This is cast in a protocol where channel estimation/prediction are jointly considered, so as to allow efficiency. The performance obtained through extensive simulations using real channels and interference show the effectiveness of the proposed scheme, both in terms of rate and reliability, at the expense of an increasing complexity. However, this solution is significantly preferable to the conventional mechanism, where channel estimation is performed only at the receiver, with channel coefficients sent back to the transmit node by means of frequent overhead signaling
Flexible Coherent Optical Access: Architectures, Algorithms, and Demonstrations
To cope with the explosive bandwidth demand, significant progress has been
made in the ITU-T standardization sector to define a higher-speed passive
optical network (PON) with a 50Gb/s line rate. Recently, 50G PON becomes mature
gradually, which means it is time to discuss beyond 50G PON. For ensuring an
acceptable optical power budget, beyond 50G PON will potentially use coherent
technologies, which can simultaneously promote the applications of flexible
multiple access such as time/frequency-domain multiple access (TFDMA). In this
paper, we will introduce the architectures, algorithms, and demonstrations for
TFDMA-based coherent PON. The system architectures based on an ultra-simple
coherent transceiver and specific signal spectra are designed to greatly reduce
the cost of ONUs. Meanwhile, fast and low-complexity digital signal processing
(DSP) algorithms are proposed for dealing with upstream and downstream signals.
Based on the architectures and algorithms, we experimentally demonstrate the
first real-time TFDMA-based coherent PON, which can support at most 256 end
users, and peak line rates of 100Gb/s and 200Gb/s in the upstream and
downstream scenarios, respectively. In conclusion, the proposed technologies
for the coherent PON make it more possible to be applied in the future beyond
50G PON.Comment: The paper has been submitted to the Journal of Lightwave Technolog
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