• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.461-462
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• 2016

IPS 측위는 GPS음영 지역인 실내의 특정 위치 정보를 판단하는 시스템으로 현재 위치에서 발생되는 신호 정보를 수집하는 시스템과 이 신호들로 구성된 실내 측위 지도, 측위 위치를 결정하기 위한 알고리즘 등에 따라 여러 종류로 나누어진다. 대표적인 IPS로 2.4Ghz, 5.0GHz 대역의 무선 신호(WiFi, BLE, Sensor Network, etc)를 활용하는 RF신호 기반 WPS 등이 있다. RF 신호를 기반으로 하는 실내 측위는 발생 기기의 고장, 장애물 발생, 채널 간섭 현상 등으로 인해 측위 시점 수집된 신호와 구축된 지도의 신호 정보가 달라 측위 정확도가 낮아지는 경우가 발생한다. 본 논문에서는 앞서 언급한 문제점을 해결하기 위해 기존 RF 환경을 사용하는 IPS 방안에 대하여 분석한다. 또한 RF 이외의 실내 측위 기술들에 대해서도 설명하고 측위 정확도를 위해 단일 측위 방식이 아닌 복합 측위 방식에 대한 설계를 제안한다.

• Journal of Advanced Navigation Technology
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• 제18권6호
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• pp.594-599
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• 2014

The routinized wireless devices such as smart phone have promoted to expand the use of IEEE 802.11 groups. The challenge environments of the wireless network utilizes effectively and user-oriented seamless services that handover is the most desirable issues under the wireless circumstance. In data center software defined network (SDN) has provided the flow routing to reduce costs and complexities. Flow routing has directly offered control for network administrator and has given to reduce delay for users. Under the circumstance of being short of network facilities, SDNs give the virtualization of network environments and to support out of the isolation traffic conditions. It shows that the mechanism of handover makes sure seamless services for higher density of the network infrastructure which is SDN to support network service re-configurable.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2118-2135
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• 2012

With the rapid development of heterogeneous emerging wireless technologies and numerous types of mobile devices, the need to support robust mobile video streaming based on the seamless handover in Future Internet is growing. To support the seamless handover, several IP-based mobility management protocols such as Mobile IPv6 (MIPv6), fast handover for the MIPv6 (FMIPv6), Hierarchical MIPv6 (HMIPv6) and Proxy Mobile IPv6 (PMIPv6) were developed. However, MIPv6 depreciates the Quality-of-Service (QoS) and FMIPv6 is not robust for the video services in heterogeneous emerging wireless networks when the Mobile Node (MN) may move to another visited network in contrast with its anticipation. In Future Internet, the possibility of mobile video service failure is more increased because mobile users consisting of multiple wireless network interfaces (WNICs) can frequently change the access networks according to their mobility in heterogeneous wireless access networks such as 3Generation (3G), Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMax) and Bluetooth co-existed. And in this environment, seamless mobility is coupled according to user preferences, enabling mobile users to be "Always Best Connected" (ABC) so that Quality of Experience is optimised and maintained. Even though HMIPv6 and PMIPv6 are proposed for the location management, handover latency enhancement, they still have limit of local mobility region. In this paper, we propose a robust mobile video streaming in Heterogeneous Emerging Wireless Systems. In the proposed scheme, the MN selects the best-according to an appropriate metric-wireless technology for a robust video streaming service among all wireless technologies by reducing the handover latency and initiation time when handover may fail. Through performance evaluation, we show that our scheme provides more robust mechanism than other schemes.

• Journal of Korea Society of Digital Industry and Information Management
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• 제11권3호
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• pp.91-98
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• 2015

There is a new evolution in technological advancement taking place called the Internet of Things (IoT), The IoT enables physical world objects in our surrounding to be connected to the Internet. ISM (Industrial Scientific Medical) band that is 2.4GHz band authorized free of charge is being widely used for smart devices. Accordingly studies have been continuously conducted on the possibility of coexistence among nodes using ISM band. In particular, the interference of IEEE 802.11b based Wi-Fi devices using overlapping channel during communication among IEEE 802.15.4 based wireless sensor nodes suitable for low-power, low-speed communication using ISM band. Because serious network performance deterioration of wireless sensor networks. In this paper, we will propose an algorithm that identifies the possibility of using more accurate channels by mixing utilization of interference signal and RSSI (Received Signal Strength Indicator) Min/Max/Activity of Interference signal by wireless sensor nodes. In addition, it will verify our algorithm by using OPNET Network verification simulator.

• Journal of Korea Multimedia Society
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• 제19권12호
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• pp.2014-2023
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• 2016

Web presence is one of the key issues for extensive deployment of Internet-of-Things (IoT). An obstacle to overcome for Web presence is relatively low computing power of IoT devices. In this paper, we present implementation of an IoT platform based on Constrained Application Protocol (CoAP) which is a web transfer protocol proposed by Internet Engineering Task Force (IETF) for the low performance IoT devices such as Wireless Sensor Network (WSN) nodes and micro-controllers. To qualify the performance of CoAP-based IoT system for such an application as smart grid, we designed a test platform consisting of Raspberry Pi2, Kmote WSN node and a desktop PC. Using open source softwares, CoAP was implemented on top of the platform. Leveraging the GET command defined at CoAP specification, performance of the system was measured in terms of round-trip time (RTT) from web application to the Kmote sensor node. To investigate abnormal cases among the test results, hop-by-hop delays were measured to analyze resulting data. The average response time of CoAP-based communication except the abnormal data was reduced by 23% smaller than the previous research result.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.290-292
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• 2009

With advance in technologies for wireless sensor networks(WSNs), 2.4 GHz band has become gradually attractive due to increase in low-power wireless communication devices. Especially ZigBee(IEEE 802.15.4-based) technology whose frequency band includes the 2.4GHz industrial, scientific and medical band providing nearly worldwide availability has been universally applicable to a various remote monitoring system and applications related home network system. However network throughput of these systems is significantly deteriorated due to this ISM band is a license-exemption used in a variety of low-power wireless communication devices. For instance, other IEEE 802 wireless standards such as Bluetooth, WLAN, Wi-Fi and others cause radio interference to ZigBee. The experiments was carried out to analyze radio frequency interference between heterogeneous devices using ISM bands to improve the limited frequency utility factor. Finally this paper suggests a frequency hopping-based adaptive multi-channel methods to decrease interference with empirical results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제23권10호
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• pp.1157-1165
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• 2012

In this paper, we measure and analyze propagation characteristic of heating, ventilation, and air conditioning(HVAC) ducts within buildings for wireless networks. We analyze the duct structures, implement the feeders exciting propagating modes, and simulate the excitation characteristic. We measure the propagation characteristic of HAVC ducts at 2.45 GHz WiFi band and compare it with that of LOS and partitioned office environments. We propose the design method of wireless network using HVAC ducts based on our results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권11호
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• pp.5223-5242
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• 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 Information Processing Systems
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• 제16권3호
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• pp.541-556
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• 2020

Wireless networks have become integral to society as they provide mobility and scalability advantages. However, their disadvantage is that they cannot control the media, which makes them vulnerable to various types of attacks. One example of such attacks is the evil twin access point (AP) attack, in which an authorized AP is impersonated by mimicking its service set identifier (SSID) and media access control (MAC) address. Evil twin APs are a major source of deception in wireless networks, facilitating message forgery and eavesdropping. Hence, it is necessary to detect them rapidly. To this end, numerous methods using clock skew have been proposed for evil twin AP detection. However, clock skew is difficult to calculate precisely because wireless networks are vulnerable to noise. This paper proposes an evil twin AP detection method that uses a multiple-feature-based machine learning classification algorithm. The features used in the proposed method are clock skew, channel, received signal strength, and duration. The results of experiments conducted indicate that the proposed method has an evil twin AP detection accuracy of 100% using the random forest algorithm.

• International Journal of Computer Science & Network Security
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• 제22권1호
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• pp.269-275
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• 2022

Public healthcare has recently become an issue of great importance due to the exponential growth in the human population, the increase in medical expenses, and the COVID-19 pandemic. Speed is one of the crucial factors in saving life, particularly in case of heart attack. Therefore, a healthcare device is needed to continuously monitor and follow up heart health conditions remotely without the need for the patient to attend a medical center. Therefore, this paper proposes a portable electrocardiogram (ECG) monitoring system to improve healthcare for heart attack patients in both home and ambulance settings. The proposed system receives the ECG signals of the patient and sends the ECG values to a MySQL database on the IoT-cloud via Wi-Fi. The signals are displayed as an ECG data chart on a webpage that can be accessed by the patient's doctor based on the HTTP protocol that is employed in the IoT-cloud. The proposed system detects the ECG data of the patient to calculate the total number of heartbeats, number of normal heartbeats, and the number of abnormal heartbeats, which can help the doctor to evaluate the health status of the patient and decide on a suitable medical intervention. This system therefore has the potential to save time and life, but also cost. This paper highlights the five main advantages of the proposed ECG monitoring system and makes some recommendations to develop the system further.