• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1608-1613
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• 2009

All kinds of equipment which used an embedded system is developed, and these are used as to an actual life in developments regarding an embedded field in a lot of sections. Also, we can collect data from all kinds of sensors through wireless sensor networks, look by real time data collected could be brought if only through embedded system. In this paper we present a plan which improve the capabilities of embedded system only act as a gateway by installing embedded database in an embedded system for the sensing data management that was transmitted by radio from sensor nodes. In other words, by installing an embedded database to store and manage data by sensing data can be reduced the transmission frequency to communicate with a host and by performing the filtering program in embedded system and then by transmitting only valid data to the host can be increase the reliability of the analysis results based on data collected.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.331-335
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• 2010

Previous low-energy time synchronization methods have mainly focused on reducing the number of transmission or reception packets. However, this paper proposes a method that reduces the percentage of time a node has to be awake (the duty cycle), assuming that a periodic sleep-wake cycle is used to conserve energy. Based on our experience with actual WSN devices, a system model is proposed, and the potential performance of the proposed method, with different parameter values, is analyzed. To further demonstrate the feasibility of our method, experiments were conducted using nine WSN devices in a $3{\times}3$ grid network topology. The results show the average synchronization error is 107.57 $\mu{s}$ in duty cycle 5% and synchronization period 10 sec, and 130 $\mu{s}$ in duty cycle 2.5% and synchronization period 20 sec.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.45-50
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• 2008

Mobile ad hoc networks (MANETs) allow mobile nodes to communicate among themselves via wireless multiple hops without the help of the wired infrastructure. Therefore, in the MANET, a route setup mechanism that makes nodes not within each other's transmission range communicate is required and, for this, the Ad-hoc On-demand Distance Vector (AODV) was proposed as one of the reactive routing protocols well suited for the characteristics of the MANET. AODV uses the hop count as the routing metric and, as a result, a node selects the farthest neighbor node as its next hop on a route, which results in a problem of deteriorating the overall network throughput because of selecting a relatively low data rate route. In this paper, we propose an efficient reactive routing protocol based on the multi-rate aware MAC. Through the simulations, we analyze the performance of our proposed mechanism and, from the simulation results, we show that our proposed mechanism outperforms the existing mechanism.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.4883-4901
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• 2016

Energy efficiency in Wireless Sensor Networks (WSNs) is very appealing research area due to serious constrains on resources like storage, processing, and communication power of the sensor nodes. Due to limited capabilities of sensing nodes, such networks are composed of a large number of nodes. The higher number of nodes increases the overall performance in data collection from environment and transmission of packets among nodes. In such networks the nodes sense data and ultimately forward the information to a Base Station (BS). The main issues in WSNs revolve around energy consumption and delay in relaying of data. A lot of research work has been published in this area of achieving energy efficiency in the network. Various techniques have been proposed to divide such networks; like grid division of network, group based division, clustering, making logical layers of network, variable size clusters or groups and so on. In this paper a new technique of group based WSNs is proposed by using some features from recent published protocols i.e. "Energy-Efficient Multi-level and Distance Aware Clustering (EEMDC)" and "Energy-Efficient Multi-level and Distance Aware Clustering (EEUC)". The proposed work is not only energy-efficient but also minimizes the delay in relaying of data from the sensor nodes to BS. Simulation results show, that it outperforms LEACH protocol by 38%, EEMDC by 10% and EEUC by 13%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3139-3145
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• 2014

This paper describes the design of a size-reduced ring hybrid coupler for microwave band using an artificial dielectric substrate(ADS). ADS structure adopts the second substrate on which has lots of the metalized via-holes. The effective capacitance and effective dielectric constant per unit length of ADS increases compared to the normal substrate due to the via-holes. This enables the physical length of microstrip transmission line to be reduced by adopting ADS instead of the normal substrate. In order to present an example of size-reduction of microwave wireless circuit by ADS, a size-reduced 3GHz ring hybrid coupler is designed, fabricated and measured in this work. The designed coupler has the smaller size from the normal one by 65% due to the ADS, while no critical degradation from ideal performances is observed. The measured power division ratio at two output ports are -3.05dB and -3.135dB, respectively. In addition, the phase differences are 3o for in-phase division and 176o for out of phase split. The measured performances are so similar to ideal ones, and prove the design of size-reduced ring hybrid coupler using ADS is successful.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.405-412
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• 2009

Mobile ad hoc networks (MANETs) allow mobile nodes to communicate among themselves via wireless multiple hops without the help of the wired infrastructure. In the MANET, it is required not only a route setup mechanism that makes nodes not within each other's transmission range communicate but also mechanism in order for a node to auto-configure a unique address. In this paper, we propose an address auto-configuration mechanism when MANET is connected to the Internet via several Internet Gateways and all gateways advertise the same network prefix. By using the proposed mechanism, once a node configures an Internet topologically correct and globally unique IP address, then the node can utilize the configured address even though the node moves within the MANET. Through the simulations, we analyze the performance of our proposed mechanism and, from the simulation results, we show that out proposed mechanism outperforms the existing mechanism.

• Journal of Korea Multimedia Society
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• v.6 no.2
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• pp.267-275
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• 2003

The development of the mobile communication has been enlarged gradually and has been changed voice centered services into data centered ones supporting Internet to provide various kinds of mobile internet services. Researches for data transmission have been achieved actively lot the effective approachment of web in the mobile terminal. The users using mobile communication are increasing for its easy handcarried and movement and the information in internet based upon wire communication has been changed into mobile communication fast. The development of mobile internet requires various mobile contents using mobile internet at any time and at any place due to rapid enhance of network capacity and mobile internet according to network expansion. To accept these needs, there are many difficult problems that contents must be remade according to various terminal features and the develoument costs much. To solve these problems, this paper has the pun)me that contents of Web documents are changed and processed through XML palter and design new mobile contents system, providing mobile services rapidly and obtaining the charge reduction result with the enhance of contents development to the shortening of a development Period.

• Journal of Korea Multimedia Society
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• v.10 no.2
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• pp.226-235
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• 2007

Recently, the lETF NEMO working group on network mobility is standardizing a basic support for moving networks. We need a handover scheme for achieving the performance of transparency during the movement of mobile routers in nested mobile networks. But existing handover schemes for a mobile host are not suitable for network mobility because the packet transmission delay and traffic increase during mobile router's handover in nested mobile networks. Therefore, we propose a new seamless handover scheme using the bi-casting based on Mobile IPv6 for nested mobile networks in this paper. Compared with the handover schemes using bi-directional edge tunneling for host mobility support on simulation. And, the results show that the proposed handover scheme reduces the packet delay during a mobile router changes the point of attachment in nested mobile networks.

• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.288-294
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• 2018

The entertainment system of the aircraft has changed its paradigm in the form of using passenger electronic devices instead of using a fixed monitor. This has simplified the on-board equipment while the risk of safety has increased with the electric charging of portable electronic devices. Unlike personal portable electronic devices that do not have a transmission function, the use of Wi-Fi enabled electronic devices(T-PED) is allowed and the battery is required to be charged in the cabin. In this study, we used the NASA Aviation Safety Reporting System to investigate the effects of changes in wireless environment and entertainment service. Based on this, we analyzed the risks of personal electronic devices by sharing event occurrence cases caused by in-flight electronic equipment or passenger portable electronic devices(especially smart phones) from the viewpoint of aircraft safety management. This analysis includes identification of potential hazards and risk assessment, and finally the strategies for risk mitigation for safe use of portable electronic devices are suggested.

• Journal of Information Processing Systems
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• v.13 no.5
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• pp.1229-1242
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• 2017

In this paper, an interference aware distributed multi-channel MAC (IDMMAC) protocol is proposed for wireless sensor and actor networks (WSANs). The WSAN consists of a huge number of sensors and ample amount of actors. Hence, in the IDMMAC protocol a lightweight channel selection mechanism is proposed to enhance the sensor's lifetime. The IDMMAC protocol divides the beacon interval into two phases (i.e., the ad-hoc traffic indication message (ATIM) window phase and data transmission phase). When a sensor wants to transmit event information to the actor, it negotiates the maximum packet reception ratio (PRR) and the capacity channel in the ATIM window with its 1-hop sensors. The channel negotiation takes place via a control channel. To improve the packet delivery ratio of the IDMMAC protocol, each actor selects a backup cluster head (BCH) from its cluster members. The BCH is elected based on its residual energy and node degree. The BCH selection phase takes place whenever an actor wants to perform actions in the event area or it leaves the cluster to help a neighbor actor. Furthermore, an interference and throughput aware multi-channel MAC protocol is also proposed for actor-actor coordination. An actor selects a minimum interference and maximum throughput channel among the available channels to communicate with the destination actor. The performance of the proposed IDMMAC protocol is analyzed using standard network parameters, such as packet delivery ratio, end-to-end delay, and energy dissipation, in the network. The obtained simulation results indicate that the IDMMAC protocol performs well compared to the existing MAC protocols.