• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.997-1005
• /
• 2010

Recently, there has been a growing interest in the use of WLAN technology due to its easy deployment, flexibility and so on. Examples of WLAN applications range from standard internet services such as Web access to real-time services with strict latency/throughput requirements such as multimedia video and voice over IP on wireless network environments. Fair and efficient distribution of the traffic loads among APs(Access Points) has become an important issue for improved utilization of WLAN. This paper focuses on an AP selection scheme for achieving better load balance, and hence increasing network resource utilization for each user on wireless network environments. This scheme makes use of active scan patterns and the network delay as main parameters of load measurement and AP selection. This scheme attempts to estimate the AP traffic loads by observing the up/down delay and utilize the results to maximize the link resource efficiency through load balancing. We compared the proposed scheme with the original SNR(Signal to Noise Ratio)-based scheme using the NS-2(Network Simulation.2). We found that the proposed scheme improves the throughput by 12.5% and lower the network up/down link delay by 36.84% and 60.42%, respectively. All in all, the new scheme can significantly increase overall network throughput and reduce up/down delay while providing excellent quality for voice and video services.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.3
• /
• pp.123-126
• /
• 2011

As the number of users of smart phone and smart pad are increasing, the deployment of WiFi APs has been accelerated. Also Internet local broadcasting service will be activated near future. But transmission error is the critical problem, due to the one-way transmission of the data to the receivers. In this paper, FER is analysed according to BER and frame length, and repetitive transmission technique is proposed to reduce the effective FER.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2007.05a
• /
• pp.855-857
• /
• 2007

In recent years, Wireless Mesh Network (WMN) is a compelling topic to many network researchers due to its low cost in deployment, ease and simplicity in installation and scalability and robustness in operation. In WMN, Gateway nodes (Access Point-AP) are in charge of steering the traffic from the external network (e.g. Internet...) to client devices or mesh clients. The limited bandwidth of wireless links between Gateways and intermediate mesh routers makes the Gateways becomes the bottleneck of the mesh network in both uplink stream and downlink stream. In this paper, we propose a mechanism to permit Gateways collaboratively work to manipulate the traffic to fit our network. They will move the traffic from congested links to the unused capacity on other links.

• Journal of Information Processing Systems
• /
• v.13 no.1
• /
• pp.26-39
• /
• 2017

The need for embedded devices to be able to exchange information with each other and with data centers is essential for the advent of the Internet of Things (IoT). Several existing communication protocols are designed for small devices including the message-queue telemetry transport (MQTT) protocol or the constrained application protocol (CoAP). However, most of the existing implementations are convenient for computers or smart phones but do not consider the strict constraints and limitations with regard resource usage, portability and configuration. In this paper, we report on an industrial research and development project which focuses on the design, implementation, testing and deployment of a MQTT module. The goal of this project is to develop this module for platforms having minimal RAM, flash code memory and processing power. This software module should be fully compliant with the MQTT protocol specification, portable, and inter-operable with other software stacks. In this paper, we present our approach based on abstraction layers to the design of the MQTT module and we discuss the compliance of the implementation with the requirements set including the MISRA static analysis requirements.

• Korean Journal of Remote Sensing
• /
• v.39 no.6_1
• /
• pp.1195-1210
• /
• 2023

Coastal debris has emerged as a salient issue due to its adverse effects on coastal aesthetics, ecological systems, and human health. In pursuit of effective countermeasures, the present study delineated the construction of a specialized image dataset for coastal debris detection and embarked on a comparative analysis between two paramount real-time object detection algorithms, YOLOv8 and RT-DETR. Rigorous assessments of robustness under multifarious conditions were instituted, subjecting the models to assorted distortion paradigms. YOLOv8 manifested a detection accuracy with a mean Average Precision (mAP) value ranging from 0.927 to 0.945 and an operational speed between 65 and 135 Frames Per Second (FPS). Conversely, RT-DETR yielded an mAP value bracket of 0.917 to 0.918 with a detection velocity spanning 40 to 53 FPS. While RT-DETR exhibited enhanced robustness against color distortions, YOLOv8 surpassed resilience under other evaluative criteria. The implications derived from this investigation are poised to furnish pivotal directives for algorithmic selection in the practical deployment of marine debris monitoring systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.3
• /
• pp.451-458
• /
• 2015

The deployment density of AP increases as well as the density WLAN stations due to increase of WLAN use and the real performance of WLAN is degraded. To improve the performance, there are many PHY/MAC technologies and OFDMA and full duplex are promising technologies among them. In conventional OFDMA WLAN MAC relate works, there are some limitations in terms of channel utilization and collision probability. Thus, it need to research for effective channel allocation protocol. Full duplex can transmit data on the same time and same frequency resource so it can allocate channel more flexible than half duplex. In this paper, we prose the OFDMA FD-MAC(Full Duplex MAC) protocol that it allocates the sub-channels based on the idle channel information for full duplex pair. In addition, it shows the throughput improvement by performance analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.11
• /
• pp.5223-5242
• /
• 2017

In the last decade, the 2.4 GHz band of IEEE 802.11 WLANs has become heavily congested due to the explosive increase in demand of Wi-Fi connectivity. With the current deployment of enterprise WLANs, channel switching mechanism continues to exhibit inefficiencies because it cannot adapt to real-time channel condition and the inability to support seamless channel switching. Software Defined Networking (SDN) as an emerging architecture is promising to introduce flexibility and programmability for wireless network management. Leveraging SDN to existing enterprise WLANs, channel switching method can be improved significantly. This paper presents a software-defined enterprise WLAN framework with a load aware automatic channel switching solution, which utilizes AP load and channel interference factor (CIF) to provide seamless channel switching. Two automatic channel switching algorithms named Single Switch (SS) and Double Switch (DS) are proposed to improve the overall user experience and the experience of users with highest traffic load respectively. Experiment results demonstrate that our solution can efficiently improve user experience in terms of jitter, transmission delay and network throughout when compared to the conventional channel switching mechanism.

• Journal of the Korea Society of Computer and Information
• /
• v.29 no.8
• /
• pp.157-164
• /
• 2024

In this paper, we propose a discussion that the feasibility of deploying a deep learning-based detector on the resource-limited board. Although many studies evaluate the detector on machines with high-performed GPUs, evaluation on the board with limited computation resources is still insufficient. Therefore, in this work, we implement the deep-learning detectors and deploy them on the compact board by parsing and optimizing a detector. To figure out the performance of deep learning based detectors on limited resources, we monitor the performance of several detectors with different H/W resource. On COCO detection datasets, we compare and analyze the evaluation results of detection model in On-Board and the detection model in On-GPU in terms of several metrics with mAP, power consumption, and execution speed (FPS). To demonstrate the effect of applying our detector for the military area, we evaluate them on our dataset consisting of thermal images considering the flight battle scenarios. As a results, we investigate the strength of deep learning-based on-board detector, and show that deep learning-based vision models can contribute in the flight battle scenarios.

• Convergence Security Journal
• /
• v.17 no.3
• /
• pp.95-101
• /
• 2017

Reliability is the priority matter in guided weapon systems. The reliability prediction data is used during the devel opment stage as the manufacturing cost is very high and the production quantity if quite limited. At the same time it takes relatively a long period of time to acquire a reliable operation data set after deployment such that in order t o determine the operational reliability, weapons must be tested and analyzed in real operating environments. For the research, the life distributions were estimated by using actual operation data and the reliability was calculated by ap plying the method of least squares and maximum likelihood estimation. Also, the comparisons were made between pr edicted reliability and actual operational reliability. As a result, the actual reliability of each system was higher than predicted reliability and it was considered that such a difference was caused by the fact that the application of the l atest designing technology and improved parts to the guided weapon systems was not reflected on the estimation of predicted reliability. It was possible to confirm the actual operational reliability of domestic (ROK) guided weapon sy stems through this research and the methods used here will contribute to the reliability analyses for the future guide d weapon systems to be developed.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.1
• /
• pp.198-205
• /
• 2007

In ubiquitous environment a user can be provided with context-aware services based on his or her current location, time, and atmosphere. LBS(Location-Based Services) play an important role for ubiquitous context-aware computing. Because deployment and maintenance of this specialized equipment is costly, many studies have been conducted on positioning using only wireless equipment under a wireless LAN infrastructure. Because a CPS(Cooperative Positioning System) that uses the RSSI (Received Signal Strength Indicator) between mobile equipments is more accurate than beacon based positioning system, it requires great concentration in its applications. This study investigates the relationship between nodes by analyzing a WiPS (Wireless LAN indoor Positioning System), a similar type of CPS, and proposes a improved WiCOPS-d(Wireless Cooperative Positioning System using node density) to increase performance by determining the convergence adjustment factor based on node density.