• Journal of Information Technology Applications and Management
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• v.12 no.4
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• pp.93-104
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• 2005

Recently, RFID/USN is one of fundamental technologies in information and communications networks. Low-Rate WPAN, IEEE802.15.4 is a low-cost communication network that allows wireless connectivity in applications with limited Power and relaxed throughput requirements. Its applications are building automation, personal healthcare, industrial control, consumer electronics, and so on. Some applications require location information. Of course location awareness is useful to improve usability of data Low-Rate WPAN Is regarded as a key specification of the sensor network with the characteristics of wireless communication, computing, energy scavenging, self-networking, and etc. Unfortunately ZigBee alliance propose a lot of applications based on location aware technologies, but the specification and low-rate WPAN devices don't support anything about location-based services. RSSI ( Received Signal Strength indication) is for energy detection to associate, channel selection, and etc. RSSI is used to find the location of a potable device in WLAN. In this paper we studied indoor location awareness using vector matching of RSSI in low-Rate wireless PAN. We analyzed the characteristics of RSSI according to distance and experimented location awareness. We implemented sensor nodes with different shapes and configured the sensor network for the location awareness with 4 fixed nodes and a mobile node. We try to contribute developing location awareness method using RSSI in 3-dimension space.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2456-2467
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• 2018

Wireless multimedia sensor networks (WMSNs) require real-time quality-of-service (QoS) guarantees to be provided by the network. The end-to-end delay is very critical metric for QoS guarantees in WMSNs. In WMSNs, due to the transmission errors incurred over wireless channels, it is difficult to obtain reliable delivery of data in conjunction with low end-to-end delay. In order to improve the end-to-end delay performance, the system has to drop few packets during network congestion. In this article, our proposal is based on optimization of end-to end delay for WMSNs. We optimize end-to-end delay constraint by assuming that each packet is allowed fixed number of retransmissions. To optimize the end-to-end delay, first, we compute the performance measures of the system, such as end-to-end delay and reliability for different network topologies (e.g., linear topology, tree topology) and against different choices of system parameters (e.g., data rate, number of nodes, number of retransmissions). Second, we study the impact of the end-to-end delay and packet delivery ratio on indoor and outdoor environments in WMSNs. All scenarios are simulated with multiple run-times by using network simulator-2 (NS-2) and results are evaluated and discussed.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.275-280
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• 2009

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner Femtocells can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage. TThe frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) forapplications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. The IEEE 1588 specification provides a low-cost means for clock synchronisation over a broadband Internet connection. The Time of Packet (ToP) specified in IEEE 1588 is able to synchronize distributed clocks with an accuracy of less than one microsecond in packet networks. However, the timing synchronization over packet switched networks is a difficult task because packet networks introduce large and highly variable packet delays. This paper proposes an enhanced filter algorithm to reduce ths packet delay variation effects and maintain ToP slave clock synchronization performance. The results are presented to demonstrate in the intra-networks and show the improved performance case when the efficient ToP filter algorithm is applied.

• Journal of Sensor Science and Technology
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• v.16 no.4
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• pp.277-285
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• 2007

In this paper, we outline the research issues that we are pursuing towards building of location aware environments for mainly ubiquitous healthcare applications. Such location aware application can provide what is happening in this space. To locate an object, such as patient or elderly person, the active ceiling-mounted reference beacons were placed throughout the building. Reference beacons periodically publish location information on RF and ultrasonic signals to allow application running on mobile or static nodes to study and determine their physical location. Once object-carried passive listener receives the information, it subsequently determines it's location from reference beacons. The cost of the system was reduced while the accuracy in our experiments was fairly good and fine grained between 7 and 12 cm for location awareness in indoor environments by using only the sensor nodes and wireless sensor network technology. Passive architecture used here provides the security of the user privacy while at the server the privacy was secured by providing the authentication using Geopriv approach. This information from sensor nodes is further forwarded to base station where further computation is performed to determine the current position of object.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.155-162
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• 2012

In this paper, we proposed a method of improving the location estimation error existing in RTLS (Real Time Location Service) system for the mobility individual. According as Ubiquitous comes, interest for indoor location tracking system was more increased socially. However, existing indoor location tracking system doesn't correspond actively in frequent change of indoor environment, and there is a problem that correct location measurement of transfer object is difficult by NLOS property of indoor environment. Purpose of this paper proposes environment accommodation location tracking system that is improved location precision of transfer object and grasps location of indoor transfer object effectively that is essential element effectively to provide service to satisfy various user's request according as Ubiquitous comes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.55-62
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• 2016

The air flows in building caused by thermal buoyancy, known as the stack effect, have a pronounced influence on both the indoor environment (thermal environment, noise, draught and contaminant diffusion) and energy needs in high-rise buildings. Prior studies for airflow in high-rise buildings were focused on the degree of stack effect and countermeasures. The wind pressure was neglected during the calculation of the indoor airflow in high-rise buildings to clarify the effect of thermal buoyancy in previous studies. However, wind is an important driving force of indoor airflows in buildings with the stack effect. In this study, the effect of wind pressure on indoor airflow in high-rise building when the stack effect is dominant in winter was analyzed. In this paper, methods that involved considering the wind pressure in airflow network simulation were analyzed.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.213-216
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• 2000

In this paper, performance of a CDMA-based packet transmission system is analyzed and simulated in a wireless infrared channel. The indoor wireless infrared channel is modeled as a non-directed diffuse link. The pulse position modulation (PPM) is used as a modulation scheme. From the simulation results, it is shown that the RS coding is very effective in improving the packet-delay characteristics of the CDMA-based packet transmission system. The performance improvement is more significant especially when the infrared channel is in a worse condition.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.241-244
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• 2005

In this paper, we construct UWB system formed by MIMO(Multi-input Multi-output) antennas using indoor WPAN(Wireless Personal Area Network) channel modeling and analyze the interference among these channels.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.11-12
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• 2006

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.235-243
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• 2014

In this paper, we propose an efficient control system for intelligent LED indoor lighting. The proposed an efficient control system for intelligent LED indoor lighting were included to elements such as daylight intensity measured through the PIR sensor and illuminance sensor at lighting style by the schedule defined and the occupancy detection. And it was controlled lighting through to the wireless sensor network, and was designed for the energy savings. Also, the lighting control of indoor lighting based on occupancy detection detect fine movements using a PIR sensor. And an unnecessary lighting intensity control of the window-side and the inside were controlled according to daylight level measurement result using the light sensor. In daylight inflow many case, the window-side lighting was to automatically darker, and in daylight inflow less case, was designed to be automatically bright. The efficiency validate results of an efficient control system for intelligent LED indoor lighting, the brightness of the indoor light were to maximize the energy saving by controlling in real time when entering as indoor a little that external lighting or daylight.