• Title/Summary/Keyword: computer simulations

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OFDM based mimicking dolphin whistle for covert underwater communications (OFDM 기반 돌고래 휘슬음 모방 수중 은밀 통신 기법)

  • Lee, Hojun;Ahn, Jongmin;Kim, Yongcheol;Seol, Seunghwan;Kim, Wanjin;Chung, Jaehak
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.3
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    • pp.219-227
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    • 2021
  • This paper proposed an Orthogonal Frequency Division Multiplexing (OFDM) based biomimetic communication method using a dolphin whistle which covertly transmits communication signals to allies. The proposed method divides the dolphin whistle into several time slots corresponding to a number of OFDM symbols, and modulates the communication signal by mapping differential phase shift keying (DPSK) symbols into subcarriers that have the frequency bands of the dolphin whistle in each slot. The advantages of the proposed method are as follows: In the conventional Chirp Spread Spectrum (CSS) and Frequency Shift Keying (FSK) based biomimetic communication methods, the discontinuity of the frequency contour is large, but the proposed method can reduce the discontinuity. Even if the modulation order is increased, the degradation of the mimicking performance is small. The computer simulations demonstrate that the Bit Error Rate (BER) and mimicking performance of the proposed method are better performance than those of the conventional CSS and FSK.

Individual Variable Step-Size Subband Affine Projection Algorithm (독립 가변 스텝사이즈 부밴드 인접투사 알고리즘)

  • Choi, Hun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.26 no.3
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    • pp.443-448
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    • 2022
  • This paper presents a subband affine projection algorithm with variable step size to improve convergence performance in adaptive filtering applications with long adaptive filters and highly correlated input signals. The proposed algorithm can obtain fast convergence speed and small steady-state error by using different step sizes for each adaptive sub-filter in the subband structure to which polyphase decomposition and noble identity are applied. The step size derived to minimize the mean square error of the adaptive filter at each update time shows better convergence performance than the existing algorithm using a variable step size. In order to confirm the convergence performance of the proposed algorithm, which is superior to the existing algorithm, computer simulations are performed for mean square deviation(MSD) for AR(1) and AR(2) colored input signals considering the system identification model.

Detection Performance Analysis of Underwater Vehicles by Long-Range Underwater Acoustic Communication Signals (장거리 수중 음향 통신 신호에 의한 수중 운동체 피탐지 성능 분석)

  • Hyung-Moon, Kim;Jong-min, Ahn;In-Soo, Kim;Wan-Jin, Kim
    • Journal of the Korea Society for Simulation
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    • v.31 no.4
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    • pp.11-22
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    • 2022
  • Unlike a short-range, a long-range underwater acoustic communication(UWAC) uses low frequency signal and deep sound channel to minimize propagation loss. In this case, even though communication signals are modulated using a covert transmission technique such as spread spectrum, it is hard to conceal the existence of the signals. The unconcealed communication signal can be utilized as active sonar signal by enemy and presence of underwater vehicles may be exposed to the interceptor. Since it is very important to maintain stealthiness for underwater vehicles, the detection probability of friendly underwater vehicles should be considered when interceptor utilizes our long-range UWAC signal. In this paper, we modeled a long-range UWAC environment for analyzing the detection performance of underwater vehicles and proposed the region of interest(ROI) setup method and the measurement of detection performance. By computer simulations, we yielded parameters, analyzed the detection probability and the detection performance in ROI. The analysis results showed that the proposed detection performance analysis method for underwater vehicles could play an important role in the operation of long-range UWAC equipment.

Helmet and Mask Classification for Personnel Safety Using a Deep Learning (딥러닝 기반 직원 안전용 헬멧과 마스크 분류)

  • Shokhrukh, Bibalaev;Kim, Kang-Chul
    • The Journal of the Korea institute of electronic communication sciences
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    • v.17 no.3
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    • pp.473-482
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    • 2022
  • Wearing a mask is also necessary to limit the risk of infection in today's era of COVID-19 and wearing a helmet is inevitable for the safety of personnel who works in a dangerous working environment such as construction sites. This paper proposes an effective deep learning model, HelmetMask-Net, to classify both Helmet and Mask. The proposed HelmetMask-Net is based on CNN which consists of data processing, convolution layers, max pooling layers and fully connected layers with four output classifications, and 4 classes for Helmet, Mask, Helmet & Mask, and no Helmet & no Mask are classified. The proposed HelmatMask-Net has been chosen with 2 convolutional layers and AdaGrad optimizer by various simulations for accuracy, optimizer and the number of hyperparameters. Simulation results show the accuracy of 99% and the best performance compared to other models. The results of this paper would enhance the safety of personnel in this era of COVID-19.

Implementation of Exclusive OR-Based Video Streaming System (배타적 논리합 기반 비디오 스트리밍 시스템의 구현)

  • Lee, Jeong-Min;Ban, Tae-Won
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.26 no.7
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    • pp.1091-1097
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    • 2022
  • In this paper, we implement the eXclusive OR-based Cast (XC) system that is a video streaming system using exclusive OR operations, and measure various performance metrics in wireless local area network (WLAN) environments. In addition, we investigate the performance improvement of the XC system considering various practical video streaming environments, while conventional studies analyzed the performance of XC through computer simulations in limited environments. To this end, we propose new control messages such as STR_REQ_MSG (SRM) that clients transmit to a video streaming server and STR_CON_MSG (SCM) that is used for the video streaming server to control the clients, and develop a new protocol by using the new control messages. According to the various measurement results using the implemented XC system, XC video streaming system can reduce the consumption of network bandwidth by 8.6% on average and up to 25% compared to the conventional video streaming system. In addition, the outage probability can be also reduced up to 76%.

Policy for Selective Flushing of Smartphone Buffer Cache using Persistent Memory (영속 메모리를 이용한 스마트폰 버퍼 캐시의 선별적 플러시 정책)

  • Lim, Soojung;Bahn, Hyokyung
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.22 no.1
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    • pp.71-76
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    • 2022
  • Buffer cache bridges the performance gap between memory and storage, but its effectiveness is limited due to periodic flush, performed to prevent data loss in smartphones. This paper shows that selective flushing technique with small persistent memory can reduce the flushing overhead of smartphone buffer cache significantly. This is due to our I/O analysis of smartphone applications in that a certain hot data account for most of file writes, while a large proportion of file data incurs single-writes. The proposed selective flushing policy performs flushing to persistent memory for frequently updated data, and storage flushing is performed only for single-write data. This eliminates storage write traffic and also improves the space efficiency of persistent memory. Simulations with popular smartphone application I/O traces show that the proposed policy reduces write traffic to storage by 24.8% on average and up to 37.8%.

Real-time Task Aware Memory Allocation Techniques for Heterogeneous Mobile Multitasking Environments (이종 모바일 멀티태스킹 환경을 위한 실시간 작업 인지형 메모리 할당 기술 연구)

  • Bahn, Hyokyung
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.22 no.3
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    • pp.43-48
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    • 2022
  • Recently, due to the rapid performance improvement of smartphones and the increase in background executions of mobile apps, multitasking has become common on mobile platforms. Unlike traditional desktop and server apps, response time is important in most mobile apps as they are interactive tasks, and some apps are classified as real-time tasks with deadlines. In this paper, we discuss how to meet the requirements of heterogeneous multitasking in managing memory of real-time and interactive tasks when they are executed together on a smartphone. To do so, we analyze the memory requirement of real-time tasks, and propose a model that has the ability of allocating memory to multitasking tasks on a smartphone. Trace-driven simulations with real-world storage access traces captured by heterogeneous apps show that the proposed model provides reasonable performance for interactive tasks while guaranteeing the requirement of real-time tasks.

An Efficient SLC Transition Method for Improving Defect Rate and Longer Lifetime on Flash Memory (플래시 메모리 상에서 불량률 개선 및 수명 연장을 위한 효율적인 단일 비트 셀 전환 기법)

  • Hyun-Seob Lee
    • Journal of Internet of Things and Convergence
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    • v.9 no.3
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    • pp.81-86
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    • 2023
  • SSD (solid state disk), which is flash memory-based storage device, has the advantages of high density and fast data processing. Therefore, it is being utilized as a storage device for high-capacity data storage systems that manage rapidly increasing big data. However, flash memory, a storage media, has a physical limitation that when the write/erase operation is repeated more than a certain number of times, the cells are worn out and can no longer be used. In this paper, we propose a method for converting defective multi-bit cells into single-bit cells to reduce the defect rate of flash memory and extend its lifetime. The proposed idea distinguishes the defects and treatment methods of multi-bit cells and single-bit cells, which have different physical characteristics but are treated as the same defect, and converts the expected defective multi-bit cells into single-bit cells to improve the defect rate and extend the overall lifetime. Finally, we demonstrate the effectiveness of our proposed idea by measuring the increased lifetime of SSD through simulations.

An Efficient Resource Optimization Method for Provisioning on Flash Memory-Based Storage (플래시 메모리 기반 저장장치에서 프로비저닝을 위한 효율적인 자원 최적화 기법)

  • Hyun-Seob Lee
    • Journal of Internet of Things and Convergence
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    • v.9 no.4
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    • pp.9-14
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    • 2023
  • Recently, resource optimization research has been actively conducted in enterprises and data centers to manage the rapid growth of big data. In particular, thin provisioning, which allocates a large number of resources compared to fixedly allocated storage resources, has the effect of reducing initial costs, but as the number of resources actually used increases, the cost effectiveness decreases and the management cost for allocating resources increases. In this paper, we propose a technique that divides the physical blocks of flash memory into single-bit cells and multi-bit cells, formats them with a hybrid technique, and manages them by dividing frequently used hot data and infrequently used cold data. The proposed technique has the advantage that the physical and allocated resources are the same, such as thick provisioning, and can be used without additional cost increase, and the underutilized resources can be managed in multi-bit cell blocks, such as thin provisioning, which can allocate more resources than typical storage devices. Finally, we estimated the resource optimization effectiveness of the proposed technique through experiments based on simulations.

Designing Modularization Method for Digital Twin: Focusing on the Noodle Manufacturing Process (디지털 트윈의 모듈화 기법 설계: 면 제조 공정을 중심으로)

  • Chan Woo Kwon;Seok Hyun Song
    • The Transactions of the Korea Information Processing Society
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    • v.13 no.2
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    • pp.26-33
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    • 2024
  • There has been a recent surge of interest in the Digital Twin technology. The Digital Twin is technique for optimizing objects by simulating physical phenomena or objects through computer-based simulations. Currently, single Digital Twin is being developed to optimize processes limited to specific fields, but there is a limitation in that the independent Digital Twins cannot analyze the vast and complex processes of the real world. To overcome this, the concept of federated Digital Twin has been introduced. To date, the federated Digital Twin research has primarily focused on how to optimize macroscopic objects such as cities. However, by leveraging the interconnected nature of twins, existing implementations of the single Digital Twins can be modularized. In this study, we define the concepts and interrelationships of the single Digital Twin and the federated Digital Twin from a functional perspective related to process optimization and design a modularization technique for the single Digital Twin using the federated Digital Twin. Furthermore, this study aims to discuss the proposed methodology's efficacy by designing a model applying modularization to a real-world fabric manufacturing case.