• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.65-70
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• 2024

In recent years, research on smart factory wireless mobile communication technology that wirelessly remotely controls utilities is being actively conducted. The Wi-SUN (Wireless Smart Utility Network) Alliance proposed a Wi-SUN protocol structure suitable for building a platform such as a smart factory as a new wireless communication standardization standard based on EEE802.15.4g/e. It analyzes the performance of the IEEE802.15.4e Receiver Initiated Transmission(RIT) Mode Media Access Control (MAC) in terms of throughput and latency, and looks at considerations for efficient operation. RIT mode shows that as the check interval becomes longer, delay time and throughput decrease. It was shown that as the traffic load increases, if the RIT check interval is shortened, the delay time can be shortened and throughput can be increased. RIT mode has the advantage of low power consumption and has neutral characteristics between IEEE802.15.4 and CSL mode in terms of delay time and throughput.

• Journal of computational fluids engineering
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• v.13 no.2
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• pp.48-54
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• 2008

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication, ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.5
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• pp.486-494
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• 2014

Intelligent homes consist of ubiquitous sensors, home networks, and a context-aware computing system. These homes are expected to offer many services such as intelligent air-conditioning, lighting control, health monitoring, and home security. In order to realize these services, many researchers have worked on various research topics including smart sensors with low power consumption, home network protocols, resident and location detection, context-awareness, and scenario and service control. This paper presents the real-time metabolic rate estimation method that is based on measured heart rate for human adaptive appliance (air-conditioner, lighting etc.). This estimation results can provide valuable information to control smart appliances so that they can adjust themselves according to the status of residents. The heart rate based method has been experimentally compared with the location-based method on a test bed.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.753-757
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• 2011

The possibility of implementing nonuniform residual dispersion per span (RDPS) in optical links with net residual dispersion (NRD) controlled by precompensation and postcompensation for 960 Gbps WDM transmissions is studied and discussed. The fiber optic communication links investigated in this paper consist of inline dispersion management (DM) for each fiber spans and optical phase conjugator (OPC) at mid-way of total transmission length in order to compensate for WDM signal distortions due to group velocity dispersion (GVD) and nonlinearities. It is confirmed that the effect of nonuniform RDPS distribution on system performance is not significant. It is also confirmed that the optimal NRD is obtained to be one of two values of +10 ps/nm or -10 ps/nm, which depend on the deciding of NRD controlled by precompensation or postcompensation, and the exact RDPS configurations. The effective NRD ranges resulting eye opening penalty (EOP) below 1 dB are independent on the exact RDPS distribution for relative low launch power. Therefore, results show the possibility of implementing the flexible optical links to expand network construction for WDM transmission of high bit-rate capability.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.254-259
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• 2012

This paper presents a closely spaced two-element folded-dipole-driven quasi-Yagi array with low mutual coupling between adjacent elements. The antenna utilizes a T-junction power divider as the feeding network, with an input impedance of $50{\Omega}$. A microstrip-stub is added to the ground plane in the middle of the two elements to improve the mutual coupling characteristics. The folded dipole driver is connected to a $50{\Omega}$ microstrip line via a broadband microstrip-to-coplanar stripline transition with a quarter radial stub. A mutual coupling of less than -22 dB is measured between two folded-dipole-driven quasi-Yagi antennas with a center-to-center spacing of 30 mm ($0.55{\lambda}_0$ at 5.5 GHz). The proposed quasi-Yagi array yields a measured bandwidth of 4.75~6.43 GHz for the -10 dB reflection coefficient and a gain of 6.14~7.12 dBi within the bandwidth range.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.967-979
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• 2013

Now a day, Wireless Sensor Networks (WSNs) are being widely used in different areas one of which is healthcare services. A wireless medical sensor network senses patient's vital physiological signs through medical sensor-nodes deployed on patient's body area; and transmits these signals to devices of registered medical professionals. These sensor-nodes have low computational power and limited storage capacity. Moreover, the wireless nature of technology attracts malicious minds. Thus, proper user authentication is a prime concern before granting access to patient's sensitive and private data. Recently, P. Kumar et al. claimed to propose a strong authentication protocol for healthcare using Wireless Medical Sensor Networks (WMSN). However, we find that P. Kumar et al.'s scheme is flawed with a number of security pitfalls. Information stored inside smart card, if extracted, is enough to deceive a valid user. Adversary can not only access patient's physiological data on behalf of a valid user without knowing actual password, can also send fake/irrelevant information about patient by playing role of medical sensor-node. Besides, adversary can guess a user's password and is able to compute the session key shared between user and medical sensor-nodes. Thus, the scheme looses message confidentiality. Additionally, the scheme fails to resist insider attack and lacks user anonymity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1014-1035
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• 2013

With recent advances in wireless communication and low-power miniaturized biomedical sensor and semiconductor technologies, wireless body area networks (WBAN) has become an integral part of the disaster aid system. Wearable vital sign sensors can track patients' status and location, thus enhancing disaster rescue efficiency. In the past few years, most of the literatures in the area of disaster aid system based on WBAN have focused on issues concerning wireless sensor design, sensor miniaturization, energy efficiency and communication protocols. In this paper, we will give an overview of disaster aid, discuss about the types of network communication as well as outline related issues. We will emphasize on analyzing six key issues in employing the disaster aid system. Finally, we will also highlight some of the challenges that still need to be addressed in the future in order to help the disaster aid system be truly and widely accepted by the public.

• Journal of the Korea Society of Computer and Information
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• v.22 no.9
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• pp.91-97
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• 2017

IoT (Internet of Things) systems are based on heterogeneous hardware systems of different types of devices interconnected each other, ranging from miniaturized and low-power wireless sensor node to cloud servers. These IoT systems composed of heterogeneous hardware utilize data sets collected from a particular set of sensors or control designated actuators when needed using open APIs created through abstraction of devices' resources associated to service applications. However, previously existing IoT services have been usually developed based on vertical platforms, whose sharing and exchange of data is limited within each industry domain, for example, healthcare. Such problem is called 'data silo', and considered one of crucial issues to be solved for the success of establishing IoT ecosystems. Also, IoT services may need to dynamically organize their services according to the change of status of connected devices due to their mobility and dynamic network connectivity. We propose a way of dynamically composing IoT services under the concept of WoT (Web of Things) where heterogeneous devices across different industries are fully integrated into the Web. Our approach allows developers to create IoT services or mash them up in an efficient way using Web objects registered into multiple standardized horizontal IoT platforms where their resources are discoverable and accessible. A Web-based service composition tool is developed to evaluate the practical feasibility of our approach under real-world service development.

• Journal of Information Science Theory and Practice
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• v.5 no.3
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• pp.61-70
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• 2017

This study investigated the use of e-journals by health researchers in the Nigerian Institute of Medical Research (NIMR). A descriptive survey method was adopted for the study and a questionnaire was used for data collection. The study population was comprised of fifty-four (54) respondents who are health researchers in the institute. The data collected were presented and analyzed using tables, frequency distribution, simple percentages, and charts. The result of the study revealed that all the respondents are aware of the availability of e-journals and attest to making use of them. The study revealed that electronic journals were mostly used for the purpose of conducting research work and the PDF format was preferred for downloading e-journals. However, it was observed that low Internet connectivity and intermittent electricity supply constitute a major obstacle to the use of e-journals. The study, therefore, recommended that the institute's management invest more resources on network connectivity, particularly its bandwidth, and ensure reliable power supply.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.504-527
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• 2015

Underwater wireless sensor networks (UWSNs) are similar to the terrestrial sensor networks. Nevertheless, there are different characteristics among them such as low battery power, limited bandwidth and high variable propagation delay. One of the common major problems in UWSNs is determining an efficient and reliable routing between the source node and the destination node. Therefore, researchers tend to design efficient protocols with consideration of the different characteristics of underwater communication. Furthermore, many routing protocols have been proposed and these protocols may be classified as location-based and location-free routing protocols. Pressure-based routing protocols are a subcategory of the location-free routing protocols. This paper focuses on reviewing the pressure-based routing protocols that may further be classified into non-void avoidance protocols and void avoidance protocols. Moreover, non-void avoidance protocols have been classified into single factor based and multi factor based routing protocols. Finally, this paper provides a comparison between these protocols based on their features, performance and simulation parameters and the paper concludes with some future works on which further study can be conducted.