Applied Sciences

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27 pages, 26738 KiB

Open AccessArticle

Pseudo-Coloring as an Effective Tool to Improve the Readability of Images Obtained in an Electromagnetic Infiltration Process

by Ireneusz Kubiak and Artur Przybysz

Appl. Sci. 2023, 13(17), 9496; https://doi.org/10.3390/app13179496 - 22 Aug 2023

Cited by 2 | Viewed by 1167

Abstract

The article presents a method of improving the readability of images obtained in the process of electromagnetic infiltration for sources processing information in a visual form (texts, images). The method uses the so-called technique of pseudo-coloring. The proposed method is based on LUT [...] Read more.

The article presents a method of improving the readability of images obtained in the process of electromagnetic infiltration for sources processing information in a visual form (texts, images). The method uses the so-called technique of pseudo-coloring. The proposed method is based on LUT tables using the exponential function mapping the signal level of the compromising emanations into a point of the RGB color space. The conducted analyses showed that the proposed function determining the coefficients of the LUT table is an effective tool in the process of improving the level of visual perception, i.e., it increases the perception of shapes and the ability to extract elements from the background. In image processing, LUT can be identified as a color map, i.e., a structure that reflects the gray shade of an image pixel into its color representation in the RGB color space. The proposed method assumes the use of exponential functions for this reflection. As an assessment of the effectiveness of the proposed methods of pseudo-coloring images, both a subjective assessment based on the visual perception of a group of observers and an analytical assessment, which was carried out by analyzing the contrast of the assessed images, were adopted. This allowed for the same assessment and usefulness of the proposed function in determining the RGB value in the process of pseudo-coloring of images obtained during electromagnetic infiltration. The obtained results confirmed that the proposed method significantly improves contrast parameter of images, which is also confirmed by the visual assessment of these images. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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21 pages, 4359 KiB

Open AccessArticle

Joint Deployment Optimization of Parallelized SFCs and BVNFs in Multi-Access Edge Computing

by Ying Han, Junbin Liang and Yun Lin

Appl. Sci. 2023, 13(12), 7261; https://doi.org/10.3390/app13127261 - 18 Jun 2023

Cited by 2 | Viewed by 1230

Abstract

In multi-access edge computing (MEC) networks, parallelized service function chains (P-SFCs) can provide low-delay network services for mobile users by deploying virtualized network functions (VNFs) to process user requests in parallel. These VNFs are unreliable due to software faults and server failures. A [...] Read more.

In multi-access edge computing (MEC) networks, parallelized service function chains (P-SFCs) can provide low-delay network services for mobile users by deploying virtualized network functions (VNFs) to process user requests in parallel. These VNFs are unreliable due to software faults and server failures. A practical way to address this is to deploy idle backup VNFs (BVNFs) near these active VNFs and activate them when active VNFs fail. However, deploying BVNFs preempts server resources and decreases the number of accepted user requests. Thus, this paper proposes a reliability enhancement approach that uses BVNFs satisfying the delay requirement as active VNFs to form P-SFCs, which contributes to the delay reduction and reliability enhancement. Since the resource capacities of edge servers can only deploy a certain number of P-SFCs and BVNFs, establishing how to deploy the minimum number of P-SFCs and BVNFs to satisfy the delay and reliability requirements of mobile users and maximize the number of accepted user requests is a challenging problem. In this paper, we first model the dynamics of delay and reliability caused by VNF parallelization and BVNFs deployment, then formulate the joint deployment problem of P-SFCs and BVNFs. Next, we design an approximation algorithm to deploy critical VNFs and BVNFs on a target edge server and schedule the data traffic of user requests processed by P-SFCs. Experimental results based on real-world datasets show that our proposed algorithm outperforms two benchmark algorithms in terms of throughput, delay, reliability, and resource utilization. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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19 pages, 607 KiB

Open AccessArticle

Topology Duration Optimization for UAV Swarm Network under the System Performance Constraint

by Rui Zhou, Xiangyin Zhang, Deyu Song, Kaiyu Qin and Limei Xu

Appl. Sci. 2023, 13(9), 5602; https://doi.org/10.3390/app13095602 - 1 May 2023

Cited by 3 | Viewed by 1804

Abstract

Network topology construction plays an important role in the application of large-scale unmanned aerial vehicle (UAV) swarm. Current researches usually perform the topology construction in terms of criteria of nodes energy consumption, transmission delay and network throughput, etc. However, another important criterion, the [...] Read more.

Network topology construction plays an important role in the application of large-scale unmanned aerial vehicle (UAV) swarm. Current researches usually perform the topology construction in terms of criteria of nodes energy consumption, transmission delay and network throughput, etc. However, another important criterion, the stability of swarm network topology, which is much critical for dynamic scenarios, has not been fully considered. In this paper, a novel topology construction method for UAV swarm network based on the criterion of topology duration is proposed. Specially, the topology construction of swarm network is formulated as an optimization problem of maximizing the topology duration while satisfying the constraints of certain network throughput, end-to-end delay, and nodes energy consumption. Then, a novel Group Trend Similarity based double-head Clustering method(GTSC) is employed to solve this problem, in which group similarity of movement, intra- and inter-cluster distance, node forwarding delay, and energy strategy are comprehensively taken into account. The proposed method is effective when used to perform the network topology construction for UAV swarm, which is verified by the simulation results. Furthermore, in comparison with representative algorithms, the proposed GTSC method exhibits better performance on topology duration, network throughput, end-to-end delay and energy consumption balance especially in a large-scale swarm scenarios. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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25 pages, 3653 KiB

Open AccessArticle

Teletraffic Analysis of DoS and Malware Cyber Attacks on P2P Networks under Exponential Assumptions

by Natalia Sánchez-Patiño, Gina Gallegos-Garcia and Mario E. Rivero-Angeles

Appl. Sci. 2023, 13(7), 4625; https://doi.org/10.3390/app13074625 - 6 Apr 2023

Cited by 2 | Viewed by 1894

Abstract

Peer-to-peer (P2P) networks are distributed systems with a communication model in which no central authority governs the behavior of individual peers. These networks currently account for a considerable percentage of all bandwidth worldwide. However, this communication model also has a clear disadvantage: it [...] Read more.

Peer-to-peer (P2P) networks are distributed systems with a communication model in which no central authority governs the behavior of individual peers. These networks currently account for a considerable percentage of all bandwidth worldwide. However, this communication model also has a clear disadvantage: it has a multitude of vulnerabilities and security threats. The nature of the P2P philosophy itself means that there is no centralized server responsible for uploading, storing, and verifying the authenticity of the shared files and packets. A direct consequence of this is that P2P networks are a good choice for hackers for the spread of malicious software or malware in general since there is no mechanism to control what content is shared. In this paper, we present a mathematical model for P2P networks to study the effect of two different attacks on these systems, namely, malware and denial of service. To analyze the behavior of the cyber attacks and identify important weaknesses, we develop different Markov chains that reflect the main dynamics of the system and the attacks. Specifically, our model considers the case in which a certain number of nodes are infected with a cyber worm that is spread throughout the network as the file is shared among peers. This allows observation of the final number of infected peers when an initial number (we evaluate the system for from 1 to 14 initial nodes) of malicious nodes infect the system. For the DoS attack, our model considers the portion of peers that are unable to communicate and the average attack duration to study the performance degradation of such an attack. A two-pronged approach was used to study the impact of the attacks on P2P networks; the first focused only on the P2P network, and the second focused on the attacks and the network. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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25 pages, 7279 KiB

Open AccessArticle

Performance and Scalability Analysis of SDN-Based Large-Scale Wi-Fi Networks

by Mohsin Ali, Ali Imran Jehangiri, Omar Imhemed Alramli, Zulfiqar Ahmad, Rania M. Ghoniem, Mohammed Alaa Ala’anzy and Romana Saleem

Appl. Sci. 2023, 13(7), 4170; https://doi.org/10.3390/app13074170 - 24 Mar 2023

Cited by 8 | Viewed by 2735

Abstract

The Software-Defined Networking (SDN) paradigm is one that is utilized frequently in data centers. Software-Defined Wireless Networking, often known as SDWN, refers to an environment in which concepts from SDN are implemented in wireless networks. The SDWN is struggling with challenges of scalability [...] Read more.

The Software-Defined Networking (SDN) paradigm is one that is utilized frequently in data centers. Software-Defined Wireless Networking, often known as SDWN, refers to an environment in which concepts from SDN are implemented in wireless networks. The SDWN is struggling with challenges of scalability and performance as a result of the growing number of wireless networks in its coverage area. It is thought that SDN techniques, such as Mininet-Wi-Fi and Ryu Controller for wireless networks, can overcome the problems with scalability and performance. Existing Wi-Fi systems do not provide SDN execution to end clients, which is one reason why the capability of Wi-Fi is restricted on SDN architecture. Within the scope of this study, we analyzed Wi-Fi networks operating on SDN using the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). By utilizing a testbed consisting of Ryu Controller and Mininet-Wi-Fi, we were able to test Wi-Fi over SDN and evaluate its performance in addition to its scalability. When evaluating the performance of a network, we take into account a number of different metrics, such as bandwidth, round-trip time, and jitter. In order to assess the level of performance, the SDN-based Wi-Fi controller Ryu is linked to an increasing number of access points (1, 2, 3, and 4) as well as stations (10, 30, 50, and 100). The experimental findings obtained using Mininet-Wi-Fi indicate the scalability and dependability of the network performance provided by the SDN Wi-Fi network controller Ryu in an SDN environment. In addition, the round-trip time for TCP packets grows proportionally with the number of hops involved. A single access point is capable of simultaneously supporting up to fifty people at once. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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15 pages, 3727 KiB

Open AccessArticle

MAC-Based Compression Ratio Improvement for CAN Security

by Jinhui Piao, Shiyi Jin, Dong-Hyun Seo, Samuel Woo and Jin-Gyun Chung

Appl. Sci. 2023, 13(4), 2654; https://doi.org/10.3390/app13042654 - 18 Feb 2023

Cited by 2 | Viewed by 1571

Abstract

Information security in a controller area network (CAN) is becoming more important as the connections between a vehicle’s internal and external networks increase. Encryption and authentication techniques can be applied to CAN data frames to enhance security. To authenticate a data frame, a [...] Read more.

Information security in a controller area network (CAN) is becoming more important as the connections between a vehicle’s internal and external networks increase. Encryption and authentication techniques can be applied to CAN data frames to enhance security. To authenticate a data frame, a message authentication code (MAC) needs to be transmitted with the CAN data frame. Therefore, space for transmitting the MAC is required within the CAN frame. Recently, the Triple ID algorithm has been proposed to create additional space in the data field of the CAN frame. The Triple ID algorithm ensures every CAN frame is authenticated by at least 4 bytes of MAC without changing the original CAN protocol. However, since the Triple ID algorithm uses six header bits, there is a problem associated with low data compression efficiency. In this paper, we propose an algorithm that can remove up to 15 bits from frames compressed with the Triple ID algorithm. Through simulation using CAN signals of a Kia Sorento vehicle and an LS Mtron tractor, we show that the generation of frames containing compressed messages of 4 bytes or more is reduced by up to 99.57% compared to the Triple ID method. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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28 pages, 27159 KiB

Open AccessArticle

Number of Lines of Image Reconstructed from a Revealing Emission Signal as an Important Parameter of Rasterization and Coherent Summation Processes

by Ireneusz Kubiak, Artur Przybysz and Krystian Grzesiak

Appl. Sci. 2023, 13(1), 447; https://doi.org/10.3390/app13010447 - 29 Dec 2022

Cited by 1 | Viewed by 1157

Abstract

An important issue in the protection of information against electromagnetic penetration is the possibility of its non-invasive acquisition. In many cases, getting hold of protected information involves recreating and presenting it in a readable and understandable form. In particular, this applies to data [...] Read more.

An important issue in the protection of information against electromagnetic penetration is the possibility of its non-invasive acquisition. In many cases, getting hold of protected information involves recreating and presenting it in a readable and understandable form. In particular, this applies to data processed in graphic form and in such a form presented on the side of eavesdropping system. The effectiveness of reconstructing data in graphic form requires knowledge of raster parameters, i.e., the line length and the number of lines of the reproduced image. This article presents new measures allowing for the determination of the correct number of lines in an image. The maximum value of the measures has been proposed as a criterion for the correctness of determining the number of image lines. A predetermined number of image lines was assumed as the input data, which was determined on the basis of the analysis of the amplitude variability of the recorded revealing emission signal. The result of the considerations of the effectiveness of the measures adopted in the process of electromagnetic infiltration was the indication of methods that allow for the correct determination of the number of lines of the reproduced image. The correct number of image lines allows the use of the coherent summation algorithm of tens of images. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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21 pages, 920 KiB

Open AccessArticle

Metrics-Based Comparison of OWL and XML for Representing and Querying Cognitive Radio Capabilities

by Yanji Chen, Mieczyslaw M. Kokar, Jakub Moskal and Kaushik R. Chowdhury

Appl. Sci. 2022, 12(23), 11946; https://doi.org/10.3390/app122311946 - 23 Nov 2022

Cited by 1 | Viewed by 1256

Abstract

Collaborative spectrum access requires wireless devices to perform spectrum-related tasks (such as sensing) on request from other nodes. Thus, while joining the network, they need to inform neighboring devices and/or the central coordinator of their capabilities. During the operational phase, nodes may request [...] Read more.

Collaborative spectrum access requires wireless devices to perform spectrum-related tasks (such as sensing) on request from other nodes. Thus, while joining the network, they need to inform neighboring devices and/or the central coordinator of their capabilities. During the operational phase, nodes may request other permissions from the the controller, like the opportunity to transmit according to the current policies and spectrum availability. To achieve such coordinated behavior, all associated devices within the network need a language for describing radio capabilities, requests, scenarios, policies, and spectrum availability. In this paper, we present a thorough comparison of the use of two candidate languages—Web Ontology Language (OWL) and eXtensible Markup Language (XML)—for such purposes. Towards this goal, we propose an evaluation method for automating quantitative comparisons with metrics such as precision, recall, device registration, and the query response time. The requests are expressed in both SPARQL Protocol and RDF Query Language (SPARQL) and XML Query Language (XQuery), whereas the device capabilities are expressed in both OWL and XML. The evaluation results demonstrate the advantages of using OWL semantics to improve the quality of matching results over XML. We also discuss how the evaluation method can be applicable to other scenarios where knowledge, datasets, and queries require richer expressiveness and semantics. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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39 pages, 22754 KiB

Open AccessArticle

Measurements and Correctness Criteria for Determining the Line Length of the Data Image Obtained in the Process of Electromagnetic Infiltration

by Ireneusz Kubiak and Artur Przybysz

Appl. Sci. 2022, 12(20), 10384; https://doi.org/10.3390/app122010384 - 14 Oct 2022

Cited by 4 | Viewed by 1249

Abstract

The protection of information against electromagnetic penetration is one of the most important aspects related to the protection of information against its non-invasive acquisition. Compared to the activities of cybercriminals, the use of electromagnetic emissions in the electromagnetic infiltration process does not leave [...] Read more.

The protection of information against electromagnetic penetration is one of the most important aspects related to the protection of information against its non-invasive acquisition. Compared to the activities of cybercriminals, the use of electromagnetic emissions in the electromagnetic infiltration process does not leave any traces of activity, and the owner of the information is not aware of its loss. The most common activities of electromagnetic eavesdropping are related to the infiltration of emission sources, graphically revealing the processing of information using both analog and digital methods. This allows for the presentation of reconstructed data in the form of images. Correct display of the acquired information requires knowledge of raster parameters such as line length and the number of lines building the reconstructed image. Due to the lack of direct access to the intercepted device, knowledge in this field does not allow for the correct determination of the aforementioned parameters, and thus, for recreating an image that would contain legible and understandable data. Additionally, incorrect values of the parameters result in failure of further processing of the obtained image, e.g., by using a coherent summation of images. Therefore, it is necessary to propose a solution that will allow not so much to roughly define the raster parameters but to estimate them precisely. Moreover, it should enable the automation of the process after the implementation of an appropriate algorithm. The article proposes an algorithm for estimating the line length of the reconstructed image. The raster parameter estimated with the use of the algorithm allows for summarizing images several dozen times with a significant improvement in the image quality and readability of the data contained in it. The image summation algorithm is very often used as one of the main image processing methods in the electromagnetic infiltration process. Incorrect raster parameters often make coherent summation useless. The proposed algorithm for estimating the line length of the reconstructed image uses three methods of determining the line length of the image for a given accuracy. At the same time, criteria were indicated that must be met to determine the correct length of the image line for the assumed accuracy of estimation. Obtained results confirmed that the proposed methods and criteria are effective in the process of electromagnetic infiltration. These methods allow us to determine the line length of reconstructed images with accuracy up to

10^{- 5}

. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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10 pages, 1981 KiB

Open AccessArticle

A Testbed for Investigating the Effect of Salinity and Turbidity in the Red Sea on White-LED-Based Underwater Wireless Communication

by Ayshah S. Alatawi

Appl. Sci. 2022, 12(18), 9266; https://doi.org/10.3390/app12189266 - 15 Sep 2022

Cited by 7 | Viewed by 2306

Abstract

Several industrial and scientific underwater applications require high-speed wireless connectivity. Acoustic communications have low data rates and high latency, whereas attenuation in seawater severely limits radio frequency communications. Optical wireless communication is a promising solution, with high transmission rates (up to Gb/s) and [...] Read more.

Several industrial and scientific underwater applications require high-speed wireless connectivity. Acoustic communications have low data rates and high latency, whereas attenuation in seawater severely limits radio frequency communications. Optical wireless communication is a promising solution, with high transmission rates (up to Gb/s) and little attenuation in water at visible wavelengths. This study explores the feasibility of white-LED-based underwater optical wireless communication (UWOC) by considering Red Sea parameters. High salinity is the most prominent attribute of the Red Sea that can affect underwater communication and requires investigation. Considering this, the received signal intensity fluctuation under increasing water salinity was experimentally investigated. In the same experiment, the impact of growing turbidity was tested, as it is the most influential parameter and tends to block the entire LED-based communication system with little increase. The experimental results show that the signals are affected less by salinity and more by turbidity but are found to be sufficiently strong to be used for communication in the Red Sea. Finally, it was concluded that a white LED is capable of sending data at the maximum possible salinity values of 40 g/L. However, the turbidity can significantly limit the transmission distance to less than 60 cm. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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18 pages, 4787 KiB

Open AccessArticle

Fourier and Chirp-Z Transforms in the Estimation Values Process of Horizontal and Vertical Synchronization Frequencies of Graphic Displays

by Ireneusz Kubiak and Artur Przybysz

Appl. Sci. 2022, 12(10), 5281; https://doi.org/10.3390/app12105281 - 23 May 2022

Cited by 4 | Viewed by 1701

Abstract

The electromagnetic protection of IT devices includes a number of organizational and technical measures aimed at ensuring control over radiated and conducted revealing emissions. This is of particular importance for ensuring information security in wireless communication and the processing of data presented in [...] Read more.

The electromagnetic protection of IT devices includes a number of organizational and technical measures aimed at ensuring control over radiated and conducted revealing emissions. This is of particular importance for ensuring information security in wireless communication and the processing of data presented in graphic form. In each of these cases, the occurring electromagnetic emissions pose the risk of a lack of electromagnetic immunity to the so-called eavesdropping process based on forming revealing emissions. Included in the elements of the security chain preventing electromagnetic eavesdropping on wireless communication and the devices building such systems are activities related to the determination of the Technical Device Security Level (TDSL) or its class. The above is related to the performance of electromagnetic emissions tests and identifying which of them must be treated as revealing emissions, which are only disturbances and do not threaten the security of the processed information. It is intuitively understandable that it is particularly important to ensure the security of interfaces that process video data. The nature of the electromagnetic emission signals generated by these interfaces means that the related information can be intercepted with the use of relatively simple methods, and under favorable circumstances even with the use of a receiving device not very technologically advanced. In the case of the electromagnetic safety assessment of video devices, common practice is therefore activities aimed at reconstructing information related to the video signal. This requires the parameters of the reconstructed image appropriate for the eavesdropped device operation mode and the conditions of recording the revealing emission signals to be determined. The article presents the results of works related to the analysis of the possibility of using spectral analysis methods (Fast Fourier FFT transform and Chirp-Z transform) to automate the process of determining the above-mentioned parameters in the case of reproducing images from emission signals recorded by using the ADC analog-to-digital converter. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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16 pages, 5887 KiB

Open AccessArticle

Implementation of a Noise-Shaped Signaling System through Software-Defined Radio

by Junsung Choi, Dongryul Park, Suil Kim and Seungyoung Ahn

Appl. Sci. 2022, 12(2), 641; https://doi.org/10.3390/app12020641 - 10 Jan 2022

Cited by 5 | Viewed by 1690

Abstract

Along with the development of electromagnetic weapons, Electronic Warfare (EW) has been rising as the future form of war. Especially in the area of wireless communications, high security defense systems such as Low Probability of Detection (LPD), Low Probability of Interception (LPI), and [...] Read more.

Along with the development of electromagnetic weapons, Electronic Warfare (EW) has been rising as the future form of war. Especially in the area of wireless communications, high security defense systems such as Low Probability of Detection (LPD), Low Probability of Interception (LPI), and Low Probability of Exploitation (LPE) communication algorithms are being studied to prevent military force loss. One LPD, LPI, and LPE communication algorithm, physical-layer security, has been discussed and studied. We propose a noise signaling system, a type of physical-layer security, which modifies conventionally modulated I/Q data into a noise-like shape. To suggest the possibility of realistic implementation, we use Software-Defined Radio (SDR). Since there are certain hardware limitations, we present the limitations, requirements, and preferences of practical implementation of the noise signaling system. The proposed system uses ring-shaped signaling, and we present a ring-shaped signaling system algorithm, SDR implementation methodology, and performance evaluations of the system using the metrics of Bit Error Rate (BER) and Probability of Modulation Identification (PMI), which we obtain by using a Convolutional Neural Network (CNN) algorithm. We conclude that the ring-shaped signaling system can perform high LPI/LPE communication functioning because an eavesdropper cannot obtain the correct modulation scheme information. However, the performance can vary with the configurations of the I/Q data-modifying factors. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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13 pages, 864 KiB

Open AccessArticle

Saddle Point Approximation of Mutual Information for Finite-Alphabet Inputs over Doubly Correlated MIMO Rayleigh Fading Channels

by Yuyu Liu, Jinbao Zhang and Dan Zhang

Appl. Sci. 2021, 11(10), 4700; https://doi.org/10.3390/app11104700 - 20 May 2021

Cited by 2 | Viewed by 2004

Abstract

Given the mutual information of finite-alphabet inputs cannot be calculated concisely and accurately over fading channels, this paper proposes a new method to calculate the mutual information. First, the applicability of the saddle point method is studied, and then the mutual information is [...] Read more.

Given the mutual information of finite-alphabet inputs cannot be calculated concisely and accurately over fading channels, this paper proposes a new method to calculate the mutual information. First, the applicability of the saddle point method is studied, and then the mutual information is estimated by the saddle point approximation method with known channel state information. Furthermore, we induce the expectation of mutual information over doubly correlated multiple-input multiple-output (MIMO) Rayleigh fading channels. The validity of the saddle point approximation method is verified by comparing the numerical results of the Monte Carlo method and the saddle point approximation method under different doubly correlated MIMO fading channel scenarios. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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Comparison on MI calculated by Monte Carlo and saddle point approximation under different input types and correction parameters (<math display="inline"><semantics> <mrow> <msub> <mi>ρ</mi> <mi mathvariant="normal">T</mi> </msub> <mo>=</mo> <msub> <mi>ρ</mi> <mi>R</mi> </msub> <mo>=</mo> <mi>ρ</mi> </mrow> </semantics></math>) over doubly correlated Rayleigh fading channel model. Full article ">Figure 2
Comparison on MI calculated by Monte Carlo and saddle point approximation under different input types and correction parameters (<math display="inline"><semantics> <mrow> <msub> <mi>ρ</mi> <mi mathvariant="normal">T</mi> </msub> <mo>=</mo> <msub> <mi>ρ</mi> <mi>R</mi> </msub> <mo>=</mo> <mi>ρ</mi> </mrow> </semantics></math>) over doubly correlated Rice fading channel model. Full article ">Figure 3
Comparison on normalized MI calculated by Monte Carlo and saddle point approximation according to upper and lower bounds of <math display="inline"><semantics> <mrow> <msub> <mi>α</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> </mrow> </semantics></math> by (14) under different input types, correction parameters (<math display="inline"><semantics> <mrow> <msub> <mi>ρ</mi> <mi mathvariant="normal">T</mi> </msub> <mo>=</mo> <msub> <mi>ρ</mi> <mi>R</mi> </msub> <mo>=</mo> <mi>ρ</mi> <mo>=</mo> <mn>0.5</mn> </mrow> </semantics></math>) over doubly correlated Rayleigh fading channel model (NT = NR = 2). Full article ">Figure 4
Comparison on MI calculated by Monte Carlo and the lower bound of saddle point approximation method under different input types and correction parameters (<math display="inline"><semantics> <mrow> <msub> <mi>ρ</mi> <mi mathvariant="normal">T</mi> </msub> <mo>=</mo> <msub> <mi>ρ</mi> <mi>R</mi> </msub> <mo>=</mo> <mn>0.5</mn> </mrow> </semantics></math>) over doubly correlated Rayleigh fading channel model. Full article ">

24 pages, 3333 KiB

Open AccessArticle

Spectrum Awareness for Cognitive Radios Supported by Radio Environment Maps: Zonal Approach

by Paweł Kaniewski, Janusz Romanik, Edward Golan and Krzysztof Zubel

Appl. Sci. 2021, 11(7), 2910; https://doi.org/10.3390/app11072910 - 24 Mar 2021

Cited by 15 | Viewed by 2270

Abstract

In this paper, we present the concept of the Radio Environment Map (REM) designed to ensure electromagnetic situational awareness of cognitive radio networks. The map construction techniques based on spatial statistics are presented. The results of field tests done for Ultra High Frequency [...] Read more.

In this paper, we present the concept of the Radio Environment Map (REM) designed to ensure electromagnetic situational awareness of cognitive radio networks. The map construction techniques based on spatial statistics are presented. The results of field tests done for Ultra High Frequency (UHF) range with different numbers of sensors are shown. Exemplary maps with selected interpolation techniques are presented. Control points where the signal from licensed users is correctly estimated are identified. Finally, the map quality is assessed, and the most promising interpolation techniques are selected. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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13 pages, 1459 KiB

Open AccessArticle

A Universal Low-Complexity Demapping Algorithm for Non-Uniform Constellations

by Hao Wang, Mingqi Li and Chao Wang

Appl. Sci. 2020, 10(23), 8572; https://doi.org/10.3390/app10238572 - 30 Nov 2020

Cited by 4 | Viewed by 2255

Abstract

A non-uniform constellation (NUC) can effectively reduce the gap between bit-interleaved coded modulation (BICM) capacity and Shannon capacity, which has been utilized in recent wireless broadcasting systems. However, the soft demapping algorithm needs a lot of Euclidean distance (ED) calculations and comparisons, which [...] Read more.

A non-uniform constellation (NUC) can effectively reduce the gap between bit-interleaved coded modulation (BICM) capacity and Shannon capacity, which has been utilized in recent wireless broadcasting systems. However, the soft demapping algorithm needs a lot of Euclidean distance (ED) calculations and comparisons, which brings great demapping complexity to NUC. A universal low-complexity NUC demapping algorithm is proposed in this paper, which creates subsets based on the quadrant of the two-dimensional NUC (2D-NUC) received symbol or the sign of the in-phase (I)/quadrature (Q) component of the one-dimensional NUC (1D-NUC) received symbol. ED calculations and comparisons are only carried out on the constellation points contained in subsets. To further reduce the number of constellation points contained in subsets, the proposed algorithm takes advantage of the condensation property of NUC and regards a constellation cluster containing several constellation points as a virtual point. Analysis and simulation results show that, compared with the Max-Log-MAP algorithm, the proposed algorithm can greatly reduce the demapping complexity of NUC with negligible performance loss. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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2D-256NUC and 1D-1024NUC designed for different CRs in ATSC 3.0. (a) 2D-256NUC designed for CR = 3/15; (b) 2D-256NUC designed for CR = 13/15; (c) 1D-1024NUC designed for CR = 3/15; (d) 1D-1024NUC designed for CR = 13/15. Full article ">Figure 2
BICM system block diagram. Full article ">Figure 3
The subsets of ED comparison to calculate LLR(<math display="inline"><semantics> <mrow> <msub> <mi>b</mi> <mn>6</mn> </msub> </mrow> </semantics></math>) when the received symbol is in the first quadrant. (a) Subsets of Max-Log-MAP algorithm; (b) Subsets obtained after some constellation points are removed. Full article ">Figure 4
The subsets of ED comparison to calculate LLR(<math display="inline"><semantics> <mrow> <msub> <mi>b</mi> <mn>3</mn> </msub> </mrow> </semantics></math>) when the received symbol is in the first quadrant. (a) Subsets of Max-Log-MAP algorithm; (b) Subsets obtained after some constellation points are removed. Full article ">Figure 5
The subset of ED calculation when the received symbol is in the first quadrant. (a) Subset before using condensation characteristic; (b) Subset after using condensation characteristic. Full article ">Figure 6
BER Performance comparison of Max-Log-MAP, QCSR and SCSR algorithms over i.i.d Rayleigh channel. Results presented for 2D-256NUCs. (a) CR = 2/15; (b) CR = 6/15; (c) CR = 10/15; (d) CR = 13/15. Full article ">Figure 7
BER Performance comparison of Max-Log-MAP and SCSR demapping algorithms over i.i.d Rayleigh channel. Results presented for 1D-1024NUCs. (a) CR = 2/15; (b) CR = 6/15; (c) CR = 10/15; (d) CR = 13/15. Full article ">

16 pages, 1230 KiB

Open AccessArticle

Detection of Misconfigured BYOD Devices in Wi-Fi Networks

by Jaehyuk Choi

Appl. Sci. 2020, 10(20), 7203; https://doi.org/10.3390/app10207203 - 15 Oct 2020

Cited by 5 | Viewed by 2293

Abstract

As Bring Your Own Device (BYOD) policy has become widely accepted in the enterprise, anyone with a mobile device that supports Wi-Fi tethering can provide an active wireless Internet connection to other devices without restriction from network administrators. Despite the potential benefits of [...] Read more.

As Bring Your Own Device (BYOD) policy has become widely accepted in the enterprise, anyone with a mobile device that supports Wi-Fi tethering can provide an active wireless Internet connection to other devices without restriction from network administrators. Despite the potential benefits of Wi-Fi tethering, it raises new security issues. The open source nature of mobile operating systems (e.g., Google Android or OpenWrt) can be easily manipulated by selfish users to provide an unfair advantage throughput performance to their tethered devices. The unauthorized tethering can interfere with nearby well-planned access points (APs) within Wi-Fi networks, which results in serious performance problems. In this paper, we first conduct an extensive evaluation study and demonstrate that the abuse of Wi-Fi tethering that adjusts the clear channel access parameters has strong adverse effects in Wi-Fi networks, while providing the manipulated device a high throughput gain. Subsequently, an online detection scheme diagnoses the network condition and detects selfish tethering devices by passively exploiting the packet loss information of on-going transmissions. Our evaluation results show that the proposed method accurately distinguishes the manipulated tethering behavior from other types of misbehavior, including the hidden node problem. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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13 pages, 540 KiB

Open AccessArticle

Adaptive Relay Selection Scheme by Using Compound Channel

by Yu-Jin Na, Won-Seok Lee, Min-Jae Paek, Hyoung-Kyu Song, Duckdong Hwang and Young-Hwan You

Appl. Sci. 2020, 10(16), 5614; https://doi.org/10.3390/app10165614 - 13 Aug 2020

Cited by 1 | Viewed by 1885

Abstract

As a cellular network of the fifth generation (5G) is commercialized, mobile devices and data throughput have rapidly increased. According to the spatial density for communication increases, the nodes of cell are overloaded. Therefore, the heterogeneous ultra dense network (UDN) is suggested. Furthermore, [...] Read more.

As a cellular network of the fifth generation (5G) is commercialized, mobile devices and data throughput have rapidly increased. According to the spatial density for communication increases, the nodes of cell are overloaded. Therefore, the heterogeneous ultra dense network (UDN) is suggested. Furthermore, the techniques for selecting a relay have been proposed in the Heterogeneous Net (HetNet). The relays are needed to improve communication performance and mitigate overload of nodes. In this paper, an adaptive relay selection scheme is proposed to obtain the diversity gain from multiple relays. To enhance the reliability of communication, the proposed scheme suggests a new algorithm considering outage probability and diversity gain of compound channel. Furthermore, the selected relays use an antenna selection algorithm to improve the channel capacity. Simulation results show that the proposed scheme improves the bit error rate (BER) and the data throughput. Full article

(This article belongs to the Special Issue Wireless Communication: Applications, Security and Reliability)

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