• Journal of Sensor Science and Technology
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• v.16 no.2
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• pp.142-149
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• 2007

Wireless sensor network technology is an emerging technology consisting of small, low power, and low cost devices that integrate limited computation, sensing, and radio communication capabilities. An ad-hoc home network system based embedded system for home environment monitoring was fabricated and tested. The wireless sensor node consists of a MCU, RF transceiver and sensors (temperature, humidity and light). Wireless sensor nodes run application software for data sampling and wireless communication, that was developed using 'nesC language' which runs on TinyOS. In our tests, acquired sensors data were monitored on 6.4" TFT-LCD of base-station through IEEE802.15.4 standard wireless communication. Also, the sensor data can be monitored by client user at the terminal PC to monitor environmental status of home in real time.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.658-665
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• 2013

While the chirp signal is extensively used in radar and sonar systems for target decision in wireless communication systems, it has not been widely used for positioning in indoor environments. Recently, the IEEE 802.15.4a standard has adopted the chirp spread spectrum (CSS) as an underlying technique for low-power and low-complexity precise localization. Chirp signal based ranging solutions have been established and deployed but their ranging performance has not been analyzed in multipath environments. This paper presents a ranging performance analysis of a chirp signal and suggests a method to suppress multipath error by using a type of non-linear chirp signal. Multipath ranging performance is evaluated using a conventional linear chirp signal and the proposed non-linear chirp signal. We verify the feasibility of both methods using two-ray multipath model simulation. Our results demonstrate that the proposed non-linear chirp signal can successfully suppress the multipath error.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.352-361
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• 2013

Combining multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) with a massive number of transmit antennas (massive MIMO-OFDM) is an attractive way of increasing the spectrum efficiency or reducing the transmission energy per bit. The effectiveness of Massive MIMO-OFDM is strongly affected by the channel state information (CSI) estimation method used. The overheads of training frame transmission and CSI feedback decrease multiple access channel (MAC) efficiency and increase the CSI estimation cost at a user station (STA). This paper proposes a CSI estimation scheme that reduces the training frame length by using a novel pilot design and a novel unitary matrix feedback method. The proposed pilot design and unitary matrix feedback enable the access point (AP) to estimate the CSI of the signal space of all transmit antennas using a small number of training frames. Simulations in an IEEE 802.11n channel verify the attractive transmission performance of the proposed methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.522-523
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• 2022

In this paper, we design a gateway protocol architecture for building an IoT-based smart factory. A smart factory system consists of several terminal devices, gateways and servers, and connects them through a wireless network. The terminal device collects information from various sensors and transmits the information to the server through the gateway. The terminal device controls the actuator by receiving a control signal according to a control algorithm of the server or by manual operation. Therefore, the gateway system connects Wi-SUN, a wireless smart utility network, and the Internet, serves as a Wi-SUN coordinator, and is equipped with Modbus-TCP to interwork with SCADA.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.5
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• pp.21-30
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• 2011

In this paper, we propose a real-time service based on retransmission slot in low rate WPAN. In the proposed scheme, during the communication period of the beacon-enabled mode in LR-WPAN standard, a special GTSs is dynamically assigned for retransmission of the packet that fails during a real-time service such as voice. This provides a time diversity in the severe channel error environments to support the required QoS. Analytical results show that this scheme achieves a much higher throughput and better transmission success rate per GTS slot than conventional schemes such as a common reserved scheme in LR WPAN.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.9
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• pp.920-926
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• 2007

Establishing a fixed path for the message delivery through a wireless network is impossible due to the mobility. Among the number of routing protocols that have been proposed for wireless ad-hoc networks, the AODV(Ad-hoc On-demand Distance Vector) algorithm is suitable in the case of highly dynamic topology changes, along with ZigBee Routing(ZBR), with the exception of route maintenance. Accordingly, this paper introduces a routing scheme focusing on the energy efficiency and route discovery time for wireless alarm systems using IEEE 802.15.4-based ZigBee. Essentially, the proposed routing algorithm utilizes a cluster structure and applies ZBR within a cluster and DSR (Dynamic Source Routing) between clusters. The proposed algorithm does not require a routing table for the cluster heads, as the inter-cluster routing is performed using DSR. The performance of the proposed algorithm is evaluated and compared with ZBR using an NS2 simulator. The results confirm that the proposed Cluster-based AODV (CAODV) algorithm is more efficient than ZBR in terms of the route discovery time and energy consumption.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.2
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• pp.48-53
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• 2010

RC(Remote Control) is a technology that can efficiently control and transfer a variety of user commands to CEs. However, the existing RCs have been required various additional features such as communication between CEs, extension of communication range, low power-consumption and bi-directional communication according to the advent of new types of CE devices and its enhanced performance. Even though RC controller has many customers' requests, it is not a simple solution because most legacies work on IR-based RC. In this paper, we propose RF4CE-based Universal Remote Control Framework using Smartphone in order to solve the many constraints of IR legacies. The proposed R-URC system is designed by RF4CE platform which is a kind of de-facto standard for CE remote control communication. From the verification scenarios using various CEs and smart phone, we can see that the proposed R-URC shows the good practical usage in terms of contents sharing and smart CE control.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.337-342
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• 2009

This paper describes a robust mobile u-healthcare system with multiple physiological signs measurement capability in real time with integration of WSN(wireless sensor network) technology and CDMA(code division multiple access) network. A cellular phone receives health data in WSN and performs local physiological signs analysis at a phone processor, and then transmits abnormal data to server for further detail or precise health signal evaluation by a medical doctor over a CDMA network. Physiological signs of the patients are continuously monitored, processed and analyzed locally at cellular phone process to produce useful medical information for diagnosis and tracking purposes. By local simple analysis in cellular phone processor we can save the data transmission cost in CDMA network. By using the developed integrate ubiquitous healthcare service architecture, patients can realize self-health checking so that the prevention actions can be taken earlier. Appropriate self-monitoring and self-management can cure disease and relieve pain especially for patients who suffer from chronic diseases that need long term observation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.331-340
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• 2006

In this Paper, we propose to extend the TSS-LS(Two-Step Search scheme with Linear search based Second step) scheme which was already proposed by the authors for coherent UWB(Ultra Wide Band) systems, to rapid and reliable acquisition of noncoherent UWB systems in multipath channels. The proposed noncoherent TSS-LS employing simple energy window banks utilizes two different thresholds and search windows to achieve fast acquisition. Furthermore, the linear search is adopted for the second step in the proposed scheme to correctly find the starting point in the range of effective delay spread of the multipath channels, and to obtain reliable BER(Bit Error Rate) performance of the noncoherent UWB systems. Simulation results with multipath channel models by IEEE 802.15.3a show that the proposed two-step search scheme can achieve significant reduction of the required mean acquisition time as compared to general search schemes. ]n addition, the proposed scheme achieves quite good BER performance for large signal-to-noise ratios, which is favorably comparable to the case of ideal perfect timing.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1185-1188
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• 2005

Recently, ubiquitous computing and sensor networks are making a rapid development. These technology can enable a new way of biomedical signal processing and healthcare. that is, they can improve care giving by a more flexible acquisition of relevant vital sign data, and by providing more convenience for patients. In this paper, we realize the biomedical sensor networks by applying IEEE 802.15.4/Zigbee networks to some various biomedical sensing unit. For address this, we developed minimized zigbee module and set-up procedure using PDA. The main advantages that we achieve are interference-free operation of different body sensor networks in the vicinity, as well as intuitive usage by the nontechnical personnel.