• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1161-1167
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• 2003

The nodes of Ad hoc network are made up of location registration for sending informations and a great number of packet transmissions to maintain routing route among the nodes. Under this environment, a huge number of traffics would be generated as mobility variable occurs more than in physical network. Hence, in this paper, focused on to study the relationship of nodes to analyze the extent of the traffic in order to control the traffics of the multi-hop in Ad hoc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1604-1617
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• 2014

This paper proposes RIX-MAC (Receiver-Initiated X-MAC), a new energy-efficient MAC protocol based on an asynchronous duty cycling. RIX-MAC improves energy efficiency through utilizing short preambles and adopting the receiver-initiated approach, where RIX-MAC minimizes sender nodes' energy consumption by enabling transmitters to predict receiver nodes' wake-up times. It also reduces receiver nodes' energy consumption by decreasing the number of control frames. We use the network simulator to evaluate RIX-MAC's performance. Compared to the prior asynchronous duty cycling approaches of X-MAC and PW-MAC, the proposed protocol shows a remarkable improvement in energy-efficiency and end-to-end delay.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.73-81
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• 2003

An autonomous stair robot recognizing the stair, and climbing up and down the stair by utilizing a robot vision, photo sensors, and appropriate climbing algorithm is introduced. Four arms associated with four wheels make the robot climb up and down more safely and faster than a simple track typed robot. The robot can adjust wheel base according to the stair width, hence it can adopt to a variable width stair with different algorithms in climbing up and down. The command and image data acquired from the robot are transferred to the main computer through RF wireless modules, and the data are delivered to a remote computer via a network communication through a proper data compression, thus, the real time image monitoring is implemented effectively.

• ETRI Journal
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• v.43 no.4
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• pp.758-768
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• 2021

In this work, the secrecy of a typical wireless cooperative dual-hop non-orthogonal multiple access (NOMA)-enabled decode-and-forward (DF) relay network is investigated with the impact of collaborative and non-collaborative eavesdropping. The system model consists of a source that broadcasts the multiplexed signal to two NOMA users via a DF relay, and information security against the eavesdropper nodes is provided by a helpful jammer. The performance metric is secrecy rate and ergodic secrecy capacity is approximated analytically. In addition, a differential evolution algorithm-based power allocation scheme is proposed to find the optimal power allocation factors for relay, jammer, and NOMA users by employing different jamming schemes. Furthermore, the secrecy rate analysis is validated at the NOMA users by adopting different jamming schemes such as without jamming (WJ) or conventional relaying, jamming (J), and with control jamming (CJ). Simulation results demonstrate the superiority of CJ over the J and WJ schemes. Finally, the proposed power allocation outperforms the fixed power allocation under all conditions considered in this work.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1938-1943
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• 2005

Network human-robot interface is an important research topic. In home application, users access the robotic system directly via voice, gestures or through the network. Users explore a system by using the services provided by this system and to some extend users are enable to participate in a service as partners. A service may be provided by a robot, a group of robots or robots and other network connected systems (distributed sensors, information systems, etc). All these services are done in the network environment, where uncertainty such as the unstable network connection, the availability of the partners in a service, exists. Moreover, these services are controlled by several users, accessing at different time by different methods. Our research aimed at solving this problem to provide a high available level, flexible coordination system. In this paper, a multi-agent framework is proposed. This framework is validated by using our new concept of slave agents, a responsive multi-agent environment, a virtual directory facilitator (VDF), and a task allocation system using contract net protocol. Our system uses a mixed model between distributed and centralized model. It uses a centralized agent management system (AMS) to control the overall system. However, the partners and users may be distributed agents connected to the center through agent communication or centralized at the AMS container using the slave agents to represent the physical agents. The system is able to determine the task allocation for a group of robot working as a team to provide a service. A number of experiments have been conducted successfully in our lab environment using Issac robot, a PDA for user agent and a wireless network system, operated under our multi agent framework control. The experiments show that this framework works well and provides some advantages to existing systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.920-925
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• 2010

A home network system is made up of home devices and wire and wireless network can not only be the subject of cyber attack from a variety factors of threatening, but also have security weakness in cases of hacking, vicious code, worm virus, DoS attack, tapping of communication network, and more. As a result, a variety of problems such as abuse of private life, and exposure and stealing of personal information arose. Therefore, the necessity for a security protocol to protect user asset and personal information within a home network is gradually increasing. Thus, this dissertation designs and suggests a home network security protocol using user authentication and approach-control technology to prevent the threat by unauthorized users towards personal information and user asset in advance by providing the gradual authority to corresponding devices based on authorized information, after authorizing the users with a Public Key Certificate.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.212-217
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• 2020

We studied on the design of a sprinkler control system that communicates with the administrator's mobile through a wireless communication network and a sprinkler unit that sprays water on the vegetation area. This sprinkler control system consists of a communication module that receives an operation signal for the operation of the sprinkler unit from the administrator's mobile, and a control module that controls the sprinkler unit according to the operation signal received through the communication module. It is also designed to control sprinkler units by measuring temperature, humidity, light intensities, vibration and field images in the vegetation area in real time through sensors and camera for each of them and comparing them with established limit criteria. The sprinkler allows the administrator to control the sprinkler more easily because the administrator operates the sprinkler through the mobile from a distance, and emergency situations occur and can respond quickly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.618-624
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• 2009

In the evolution from wireless sensor networks(WSNs) to ubiquitous sensor networks(USNs), technologies that can support intensive data-traffic loads, large number of users, improved interoperability, and extreme longevity are required. Therefore, efficient communication time coordination control and low power consumption becomes one of the most important design goals for USN MAC protocols. So far several time division multiplexed (TDM) MAC protocols have been proposed. However, since the pros and cons of existing protocols are not easy to analyze, it becomes a challenging task to design improved TOM MAC protocols. Based on this objective, this paper provides a novel protocol analysis along with a message complexity derivation and comparison of the existing TDM MAC protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1031-1038
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• 2004

The call admission control algorithm of hybrid scheme is proposed to enhance the QoS(quality of service) of attempted multimedia calls. In the initial stage of 3rd generation multimedia services networks, the major limitations include the small sefyice coverage and the limited radio link capacity. Because the initial massive deployment of network elements such as base stations, base station controllers, and mobile switching centers is restricted to populated areas and the other areas should be covered with the fewer network elements, the radio channel resources are hmited and coverage network is supposed to be established. Therefore the QoS of multimedia services is expected to be severely degraded when tentative traffic hot spot occurs frequently. Thus, the blocking probability of attempted calls mcreases when relatively large number of users try to place multimedia calls in a hot spot area of the wireless networks. In this situation, the proposed hybrid scheme can mitigate the degradation of the QoS of multimedia services by using the available radio channels of the neighboring cells.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.4
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• pp.1-9
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• 2015

This paper proposes CAC method that is more efficient for RRM using game theory combined with Multiple Attribute Decision Making(MADM). Because users request services with different Quality of Service(QoS), the network preference values to alternative networks for each service are calculated by MADM methods such as Grey Relational Analysis(GRA), Simple Additive Weighting(SAW) and Technique for Order Preference by Similarity to Ideal Solution(TOPSIS). According to a utility function representing preference value, non-cooperative game is played, and then network provider select the requested service that provide maximum payoff. The appropriate service is selected through Nash Equilibrium that is the solution of game and the game is played repeated. We analyze two overlaid networks among four Wireless LAN(WLAN) systems with different properties. Simulation results show that proposed MADM techniques have same outcomes for every game round.