A sensor placement approach using multi-objective hypergraph particle swarm optimization to improve effectiveness of structural health monitoring systems

In this paper, a novel Multi-Objective Hypergraph Particle Swarm Optimization (MOHGPSO) algorithm for structural health monitoring (SHM) systems is considered. This algorithm autonomously identifies the most relevant sensor placements in a combined fitness function without artificial intervention. The approach utilizes six established Optimal Sensor Placement (OSP) methods to generate a Pareto front, which is systematically analyzed and archived through Grey Relational Analysis (GRA) and Fuzzy Decision Making (FDM). This comprehensive analysis demonstrates the proposed approach’s superior performance in determining sensor placements, showcasing its adaptability to structural changes, enhancement of durability, and effective management of the life cycle of structures. Overall, this paper makes a significant contribution to engineering by leveraging advancements in sensor and information technologies to ensure essential infrastructure safety through SHM systems

A distance vector hop-based secure and robust localization algorithm for wireless sensor networks

Location information of sensor nodes in a wireless sensor network is important. The sensor nodes are usually required to ascertain their positions so that the data collected by these nodes can be labeled with this information. On the other hand, certain attacks on wireless sensor networks lead to the incorrect estimation of sensor node positions. In such situations, when the location information is not correct, the data may be labeled with wrong location information that may subvert the desired operation of the wireless sensor network. In this work, we formulate and propose a distance vector hop-based algorithm to provide secure and robust localization in the presence of malicious sensor nodes that result in incorrect position estimation and jeopardize the wireless sensor network operation. The algorithm uses cryptography to ensure secure and robust operation in the presence of adversaries in the sensor network. As a result of the countermeasures, the attacks are neutralized and the sensor nodes are able to estimate their positions as desired. Our secure localization algorithm provides a defense against various types of security attacks, such as selective forwarding, wormhole, Sybil, tampering, and traffic replay, compared with other algorithms which provide security against only one or two types. Simulation experiments are performed to evaluate the performance of the proposed method, and the results indicate that our secure localization algorithm achieves the design objectives successfully. Performance of the proposed method is also compared with the performance of basic distance vector hop algorithm and two secure algorithms based on distance vector hop localization. The results reveal that our proposed secure localization algorithm outperforms the compared algorithms in the presence of multiple attacks by malicious nodes

Optimal learning paradigm and clustering for effective radio resource management in 5G HetNets

Ultra-dense heterogeneous networks (UDHN) based on small cells are a requisite part of the future cellular networks as they are proposed as one of the enabling technologies to handle coverage and capacity problems. But co-tier and cross-tier interferences in UDHN severely degrade the quality of service due to K-tiered architecture. Machine learning based radio resource management either through independent learning or cooperative learning is a proven efficient scheme for interference mitigation and quality of service provision in UDHN in a both distributive and cooperative manner. However, an optimal learning paradigm selection, i.e., either independent or cooperative learning and optimal cooperative cluster size in cooperative learning for efficient radio resource management in UDHN is still an open research problem. In this article, a Q-learning based radio resource management scheme is proposed and evaluated for both distributive and cooperative schemes using independent and cooperative learning. The proposed Q-learning solution follows the $\epsilon -$ greedy policy for optimal convergence. The simulation results for the UDHN in an urban setup show that in comparison to the independent learning paradigm, cooperative learning has no significant impact on macro cell user capacity. However, there is a significant improvement in small cell user capacity and the sum capacity of the cooperating small cells in the cluster. A significant increase of 48.57% and 37.9% is observed in the small cell user capacity, and sum capacity of the cooperating small cells, respectively, using cooperative learning as compared to independent learning which sets cooperative learning as an optimal learning strategy in UDHN. The improvement in small cell user capacity is at cost of increased computational time which is directly proportional to the number of cooperating small cells. To solve the issue of computational time in cooperative learning, an optimal clustering algorithm is proposed. The proposed optimal clustering reduced the computational time by four times in cooperative Q-learning

Simulated Annealing-Based Multilink Selection Algorithm in SDN-Enabled Avionic Networks

In this paper, a novel multilink selection framework is developed for different applications with various quality of service (QoS) requirements in avionic systems, based on the multi-attribute decision-making model. Two metaheuristic algorithms are proposed to solve this model while optimizing the multilink selection performances. Multilink configuration and multi-homing capabilities are generally required for aircrafts operating in a heterogeneous wireless network environment. The first algorithm, called Analytic Hierarchy Process and Simulated Annealing (AHP-SA), utilizes a two-phase process. In Phase one, an analytic hierarchy process (AHP) is used to choose the decision weight factors. Then, in Phase two, a simulated annealing process is applied to select suitable networks, for various service requests, based on the weights obtained from first phase. Further, to improve customer satisfaction, Simulated Annealing algorithm for Simultaneous Weights and Network Selection Optimisation (SA-SWNO) is developed, in which a simulated annealing algorithm is applied to dynamically optimize weight factors of objective functions and the request-to-network assignment matrix. Simulation results demonstrate that both proposed algorithms outperform the commonly used price-based or QoS-based network selection scheme with much higher averaged satisfaction degree and lower computational complexity

Simulated Annealing-based Multilink Selection Algorithm in SDN-enabled Avionic Networks

YesIn this paper, a novel multilink selection framework is developed for different applications with various quality of service (QoS) requirements in avionic systems, based on the multi-attribute decisionmaking model. Two metaheuristic algorithms are proposed to solve this model while optimizing the multilink selection performances. Multilink configuration and multi-homing capabilities are generally required for aircrafts operating in a heterogeneous wireless network environment. The first algorithm, called Analytic Hierarchy Process and Simulated Annealing (AHP-SA), utilises a two-phase process. In Phase one, an analytic hierarchy process (AHP) is used to choose the decision weight factors. Then, in Phase two, a simulated annealing process is applied to select suitable networks, for various service requests, based on the weights obtained from first phase. Further, to improve customer satisfaction, Simulated Annealing algorithm for Simultaneous Weights and Network Selection Optimisation (SA-SWNO) is developed, in which a simulated annealing algorithm is applied to dynamically optimise weight factors of objective functions and the request-to-network assignment matrix. Simulation results demonstrates that both proposed algorithms outperform the commonly used price-based or QoS-based network selection scheme with much higher averaged satisfaction degree and lower computational complexity.Cockpit NetwOrk CoMmunications Environment Testing (COMET) Project under the European Commission’s Program Clean Sky2 in partnership with the European Aeronautical Industr

Analysis and Application of Digital Backward Propagation in High Bit-Rate Optical Transmission Systems

In neuesten numerischen und experimentellen Untersuchungen haben sich die Modulationsformate kohärentes optisches QPSK mit Polarisationsmultiplex (DP-CO-QPSK) und QAM als äußerst vielversprechend für die Realisierung von 100 Gbit/s Ethernet der nächsten Generation (100 GbE) und noch höheren Datenraten von z.B. 224 Gbit/s und 400 Gbit/s erwiesen. Kohärente Detektion in Verbindung mit digitaler Signalverarbeitung (DSP) stellt eine effiziente Methode zur Kompensation diverser linearer Effekte, wie z.B. chromatische Dispersion (CD) und Polarisationsmodendispersion (PMD) bei der Übertragung über Glasfasern dar und weist weiterhin geringe Anforderungen an das optische Signal-zu-Rausch-Verhältnis (OSNR) auf. Trotz Faserdispersion und Nichtlinearitäten, welche die bedeutendsten limitierenden Faktoren darstellen, werden in optischen Übertragungssystemen höherwertige Modulationsformate eingesetzt, um die spektrale Effizienz zu erhöhen und somit die stetig wachsende Nachfrage nach größeren Übertragungskapazitäten zu erfüllen. Daraus resultierend ist die Thematik der Kompensation linearer Effekte wie z.B. chromatischer Dispersion und von Nichtlinearitäten wie z.B. Selbstphasenmodulation (SPM), Kreuzphasenmodulation (XPM) und Vierwellenmischung (FWM) derzeit von hohem Interesse. Im Rahmen dieser Arbeit wurde der ‚Digital Backward Propagation‘ (DBP) Algorithmus zur gleichzeitigen Kompensation linearer und nichtlinearer Verzerrungen bei der Übertragung über Glasfasern in Systemen mit höheren Datenraten und fortgeschrittenen Modulationsformaten eingehend untersucht. DBP basiert auf der numerischen Umsetzung der inversen nichtlinearen Schrödinger Gleichung (NLSE) unter Verwendung von ‚Split-Step Fourier Methoden‘ (SSFM). Die Einflüsse: (a) der Datenrate, z.B. 10 Gbit/s, 40 Gbit/s und 100 Gbit/s; (b) der Länge der faseroptischen Übertragungsstrecke und (c) von Einkanal- im Vergleich zu Mehrkanal-Übertragung auf die Leistungsfähigkeit des DBP Algorithmus werden ausgewertet. Für diese Untersuchungen kommen gängige SSFM Methoden zum Einsatz, wie z.B. die Asymmetrische Split-Step Fourier Methode (A-SSFM) und die Symmetrische Split-Step Fourier Methode (S-SSFM). Basierend auf der Analyse dieser Resultate wurde eine neue Methode vorgeschlagen, die als Modifizierte DBP (M-DBP) bezeichnet wird und SSFM verwendet, welche durch eine Optimierung des Berechnungspunktes des nichtlinearen Operators (r) umgesetzt wird. Normalerweise beträgt r = 0 für A-SSFM und r = 0.5 für S-SSFM, wohingegen für M_DBP 0 ≤ r ≤ 0.5 beträgt. Der Einfluss der Auswahlmethode zur Bestimmung der Schrittweite auf die Leistungsfähigkeit des DBP wurde ebenfalls untersucht. Bisherige Algorithmen und mathematische Modelle des DBP werden mit SSFM Methoden mit konstanter Schrittweite umgesetzt. Die numerischen Ergebnisse machen ersichtlich, dass die nichtlineare Toleranz durch Verwendung des DBP Algorithmus basierend auf einer logarithmischen Schrittweite (L-DBP) verbessert wird. Ich habe diesen Algorithmus in 56 Gbit/s, 112 Gbit/s, 224 Gbit/s DP-QPSK Systemen mit WDM Übertragung von 20, 10 und 5 Kanälen untersucht. Weiterhin wurde das Konzept der gefilterten nichtlinearen Schritte beim L-DBP angewendet und mittels des auf einer logarithmischen Schrittweite basierende DBP Algorithmus mit interner Filterung (FL-DBP) konnte der Rechenaufwand um bis zu 75% reduziert werden, d.h. Multi-Span DBP, was bedeutet, dass ein Berechnungsschritt über mehrere Faserspans durchgeführt wird. Ein weiterer Ansatz der angewendet wurde um die Systemeigenschaften des DBP zu verbessern ist die Berücksichtigung der Optimierung der Pulsformen. Verschiedene Pulsformen wurden untersucht, darunter: Non-return to zero (NRZ), Return to zero (RZ) und Root Raised Cosine (RRC) Pulse in einem 112 Gbit/s DP-QPSK Übertragungssystem. Die Ergebnisse zeigen anschaulich, dass die RRC Pulsformung toleranter bezüglich Intra-Kanal Nichtlinearitäten ist, d.h. SPM, und folglich die Nichtlineare Schwelle des Übertragungssystems erhöht. Die Toleranzen des DBP Algorithmus gegenüber Schwankungen, die die Informationen über den Aufbau der Übertragungsstrecke betreffen, wurde ebenfalls eingehend geprüft. Zum Abschluss der Dissertation fokussiere ich mich auf ein 224 Gbit/s DP-16QAM Übertragungssystem, um die Leistungsfähigkeit der M-DBP und L-DBP Algorithmen für verschiedene Fasertypen in homogenen wie auch inhomogenen Faserstrecken zu vergleichen. Diese Untersuchung wird weiterhin ausgeweitet auf den Vergleich von DP-16QAM mit einem Modulationsformat mit gleicher spektraler Effizienz, d.h. Duobinär mit Quadraturphase und Polarisationsmultiplex (DP-QDB), wobei die Komplexität des DBP Algorithmus für beide Formate analysiert wird. Die Hauptmotivation für die Serie von numerischen Untersuchungen hinsichtlich der Übertragung mittels Polarisationsmultiplex liegt in der Untersuchung der Leistungsfähigkeit des DBP Algorithmus bei erhöhter Übertragungskapazität im Vergleich zur Übertragung mittels einer einzelnen Polarisation. Ungeachtet der Tatsache, dass die Leistungsfähigkeit von Übertragungssystemen mit Polarisationsmultiplex von der Polarisationsmodendispersion (PMD) abhängt, wird diese im Rahmen dieser Arbeit als vernachlässigbar angesehen. Auch dass PMD einen stochastischen Prozess darstellt und der DBP Algorithmus lediglich deterministische Beeinflussungen kompensieren kann. Die wichtigste Zielsetzung dieser Arbeit liegt in der Bereitstellung eines Leitfadens zum Verständnis des DBP Algorithmus im Falle unterschiedlicher Methoden der Implementierung, unterschiedlicher Übertragungssysteme und Auslegung der Übertragungsstrecke. Die vorliegenden numerischen Untersuchungen werden weiterhin beim zukünftigen Einsatz der DBP Algorithmen in Modulen mit Echtzeit-Signalverarbeitung zur digitalen nichtlinearen Entzerrung hilfreich sein.Recent numerical and experimental studies have shown that dual polarization coherent optical QPSK (DP-CO-QPSK) and QAM modulation formats are the strong candidates for implementing next-generation 100Gbit/s Ethernet (100 GbE) and also for higher bit-rates, i.e. 224Gbit/s and 400Gbit/s. Coherent detection is considered efficient along with digital signal processing (DSP) to compensate many linear effects in fiber propagation i.e. chromatic dispersion (CD) and polarization-mode dispersion (PMD) and also offers low required optical signal-to-noise ratio (OSNR). Despite of fiber dispersion and non-linearities which are the major limiting factors, optical transmission systems are employing higher order modulation formats in order to increase the spectral efficiency and thus fulfill the ever increasing demand of capacity requirements. As a result of which compensation of linear effects i.e chromatic dispersion (CD) and non-linearities (NL), i.e. self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM), is a point of high interest these days. In this thesis, the detailed study on the Digital Backward Propagation (DBP) algorithm for the joint compensation of linear and non-linear fiber transmission impairments in the systems with higher bit-rates and advanced modulation formats has been performed. DBP is based on the numerical implementation of inverse non-linear Schrodinger equation (NLSE) by using split-step Fourier (SSFM) methods. The impact of: (a) bit-rate, i.e. 10Gbit/s, 40Gbit/s and 100Gbit/s; (b) fiber transmission length and (c) single channel vs. multi-channel transmission, on the performance of DBP algorithm are evaluated. In these investigations, the conventional SSFM methods, i.e. Asymmetric split-step Fourier method (A-SSFM) and Symmetric split-step Fourier method (S-SSFM) are used. Based on the analysis of these results, a new method has been proposed, called as Modified DBP (M-DBP), using SSFM which is implemented by optimizing the non-linear operator calculation point (r). Usually r=0 in A-SSFM and r=0.5 in S-SSFM, whereas 0<r<0.5 for M-DBP. The impact of step-size selection method on the performance of DBP has also been investigated. Previous algorithms and mathematical models of DBP are implemented with constant step-size SSFM methods. From the numerical results it is evident that the non-linear tolerance of the system is improved by using the logarithmic step-size based DBP algorithm (L-DBP). I have investigated this algorithm in 56Gbit/s, 112Gbit/s, 224Gbit/s dual-polarization (DP-) QPSK systems with 20,10 and 5 channels WDM transmission. Furthermore, the concept of filtered non-linear step is implemented with L-DBP and filtered-logarithmic step-size based DBP (FL-DBP) algorithm efficiently reduced the computational efforts of the algorithm up to 75%, i.e. multi-span DBP, which means that one calculation step is processed over several spans of fiber. Another approach which has been adopted to improve the system performance of DBP is by taking into account the optimization of pulse shapes. Diverse pulse shapes has been investigated, such as: non-return to zero (NRZ), return to zero (RZ) and root raised cosine (RRC) pulses, with 112Gbit/s DP-QPSK transmission system. The results depict that RRC pulse shaping is more tolerant to intra-channel non-linearities, i.e. SPM, hence enhancing the non-linear threshold point of the transmission system. The tolerance of DBP algorithm with variations in link design information is scrutinized as well. For the conclusion of the dissertation, I focus on 224Gbit/s DP-16QAM transmission system to compare the performance of M-DBP with L-DBP algorithms over different kinds of fiber in homogeneous fiber links as well as in-homogeneous fiber links. This study is further extended to compare DP-16QAM with same spectrally efficient modulation format, i.e. dual-polarization quadrature duo-binary modulation (DP-QDB), and the complexity of the DBP algorithm for both the formats is analysed. The main motivation for the series of numerical analysis on dual polarization transmission is to actually investigate the performance of DBP algorithm with increased transmission capacity as compared to single polarization transmission. Despite of the fact that, the performance of dual polarization transmission systems are dependent on polarization mode dispersion (PMD), it is considered negligible in this thesis. Also that PMD is a stochastic process and the DBP algorithm only compensates the deterministic impairments. The main objective of this work is to provide a guide to apprehend the knowledge on the DBP algorithm with different implementation methods, transmission systems and link designs. These numerical investigations will also be helpful in future deployment of DBP algorithm with real-time signal processing modules for digital non-linear compensation

Effective negative Kerr non-linear coefficient using highly non-linear fibers:A scalable backward propagation approach

We have numerically evaluated optical backward propagation (OBP) by the conjunction of dispersion compensating fiber (DCF) and a non-linear compensator (NLC) devised by effective negative Kerr non-linear coefficient using two highly non-linear fibers (HNLF) to compensate fiber transmission impairments, i.e. chromatic dispersion (CD) and non-linearities (NL). The OBP module is evaluated for dual-polarization (DP) mary (m=4,16,32,64,256) quadrature amplitude modulation (QAM) in 112 Gbit/s coherent transmission over standard single mode fiber (SMF). We have also proposed a intensity limited optical backward propagation module (IL-OBP) by using a self-phase modulation-based optical limiter with an appropriate pre-chirping to compensate for the intensity fluctuations in the transmission link. Our results depict that in highly non-linear sensitive 256QAM transmission, we have observed a 40% increase in the transmission distance by implementing IL-OBP as compared to conventional OBP

All-optical signal processing of fiber impairments in dual-polarization 112 Gbit/s m-ary QAM coherent transmission

We have numerically implemented a receiver side all-optical signal processing method, i.e. optical backward propagation (OBP), by dispersion compensating fiber (DCF) and non-linear compensator (NLC) devised by effective negative Kerr non-linear coefficient using two highly non-linear fibers (HNLFs). The method is implemented for the post-processing of fiber transmission impairments, i.e. chromatic dispersion (CD) and non-linearities (NL). The OBP module is evaluated for dual-polarization (DP) m-ary (m=4, 16, 32, 64, 256) quadrature amplitude modulation (QAM) in 112 Gbit/s coherent transmission over 1200 km standard single mode fiber (SMF). We have also investigated an intensity limited optical backward propagation module (IL-OBP) by using a self-phase modulation-based optical limiter with an appropriate pre-chirping to compensate for the intensity fluctuations in the transmission link. Our results show that in highly non-linear sensitive 256QAM transmission, we have observed a 66% increase in the transmission distance by implementing IL-OBP as compared to conventional OBP

Performance analysis of BER optimization in WDM systems using EDFA

Wavelength division multiplexing (WDM) systems, which are widely used in telecommunication, have the advantages of huge bandwidth support and reliability. A performance analysis is presented of a WDM system using an erbium-doped fiber amplifier (EDFA), with specific emphasis on bit error rate (BER) optimization. EDFA parameters, including doped fiber length and pump power, are optimized and performance evaluating parameters for different modulation schemes are observed. Simulation results provide optimized BER, noise figure, and gain flatness values. The WDM system is modeled from 1546 nm to 1558 nm bandwidth to obtain maximum gain uniformity, low noise figure, and low BER. This wavelength range is selected to investigate the 1550 nm wavelength commonly used in the telecommunication industry. Also, that we are using a WDM grid, so multiple channels can be accommodated in this range