• Journal of Institute of Control, Robotics and Systems
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• v.11 no.12
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• pp.991-995
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• 2005

Sensor networks are the results of convergence of very important technologies such as wireless communication and micro electromechanical systems. In recent years, sensor networks found a wide applicability in various fields such as health, environment and habitat monitoring, military, etc. A very important step for these many applications is pattern classification and recognition of data collected by sensors installed or deployed in different ways. But, pattern classification and recognition are sometimes difficult to perform. Systematic approach to pattern classification based on modern teaming techniques like Multivariate Gaussian mixture models, can greatly simplify the process of developing and implementing real-time classification models. This paper proposes a new recognition system which is hierarchically composed of many sensor nodes haying the capability of simple processing and wireless communication. The proposed system is able to perform classification of sensed data using the Multivariate Gaussian function. In order to verify the usefulness of the proposed system, it was applied to hand gesture recognition system.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.166-171
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• 2015

Recently, the international standard RS-422 serial communication, which was primarily designed for the communications between micro-controllers, has been used as a communication method on the ship. However, as the NMEA (National Marine Electronics Association) 2000 standardization progresses recently, a high-speed Ethernet-based communication environment is expected to be an alternative communication method instead of the RS-422 gradually. In addition, the ship's main instrumentation equipment with versatility and convenience is implemented to control devices as monitoring and controlling tools. This paper describes an implementation of wireless ultrasonic anemometer and anemoscope data processing and logger system using PC network, where the control processing equipment such as a separate operational console, data-logger, and indicator is required for the system. For these, the related element technologies to implement ultrasonic anemometer and anemoscope data processing system are expressed as a functional modules, and the NMEA 2000 standard certified data-logger system is implemented without the separate operational console.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.7
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• pp.711-717
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• 2007

Location information will become increasingly important for future Pervasive Computing applications. Location tracking system of a moving device can be classified into two types of architectures: an active mobile architecture and a passive mobile architecture. In the former, a mobile device actively transmits signals for estimating distances to listeners. In the latter, a mobile device listens signals from beacons passively. Although the passive architecture such as Cricket location system is inexpensive, easy to set up, and safe, it is less precise than the active one. In this paper, we present a passive location system using Cricket Mote sensors which use RF and ultrasonic signals to estimate distances. In order to improve accuracy of the passive system, the transmission speed of ultrasound was compensated according to air temperature at the moment. Upper and lower bounds of a distance estimation were set up through measuring minimum and maximum distances that ultrasonic signal can reach to. Distance estimations beyond the upper and the lower bounds were filtered off as errors in our scheme. With collecting distance estimation data at various locations and comparing each distance estimation with real distance respectively, we proposed an equation to compensate the deviation at each point. Equations for proposed algorithm were derived to calculate relative coordinates of a moving device. At indoor and outdoor tests, average location error and average location tracking period were 3.5 cm and 0.5 second, respectively, which outperformed Cricket location system of MIT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.445-450
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• 2012

We have developed an implantable wireless sensor for real time pressure monitoring of blood circulation system. MEMS (micro-electro-mechanical system) technology was adopted as a sensor development method. The sensor is composed of photolithographically patterned inductors and a distributed capacitor in gap between the inductors. A resulting LC resonant system produces its resonant frequency in range of 269 to 284 MHz at 740 mmHg. To read the resonant frequency changed by blood pressure variation, we developed a custom readout system based on a network analyzer functionality. The bench-top testing of the pressure sensors showed good mechanical and electrical functionality. A sensor was implanted into tibial artery of farm pig, and interrogated wirelessly with accurate readings of blood pressure. After 45 days, the sensor's electrical response and histopathology were studied with good frequency reading and biocompatibility.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4436-4452
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• 2015

The IEEE 802.15.6 standard is introduced to satisfy all the requirements for monitoring systems operating in, on, or around the human body. In this paper, analytical models are developed for evaluating the performance of the IEEE 802.15.6 CSMA/CA-based medium access control protocol for wireless body area networks (WBAN) under unsaturation condition. We employ a three-dimensional Markov chain to model the backoff procedure, and an M/G/1/K queuing system to describe the packet queues in the buffer. The throughput and delay performances of WBAN operating in the beacon mode are analyzed in heterogeneous network comprised of different user priorities. Simulation results are included to demonstrate the accuracy of the proposed analytical model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.257-263
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• 2003

Error control and concealment in video communication is becoming increasingly important because transmission errors can cause single or multiple loss of macroblocks in video delivery over unreliable channels such as wireless networks and the internet. This paper describes a temporal error concealment by postprocessing. Lost image blocks are overlapped block motion compensated (OBMC) using median of motion vectors from adjacent blocks at the decoder. The results show a significant improvement over zero motion error concealment and other temporal concealment methods such as Motion Vector Rational Interpolation or Side Match Criterion OBMC by 1.4 to 3.5㏈ gain in PSNR. We present experimental results showing improvements in PSNR and computational complexity.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.8
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• pp.738-743
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• 2012

This paper describes analysis of long-term experiments on a monitoring system to assess the daily activities of the elderly who live alone. The developed system is composed of an in-house sensing system and a server system. The in-house sensing system installed in their own houses is a typical wireless sensor network system including three kinds of wireless sensors. The server system has a database server and an assessment server. We have installed the system into an elderly house, collected data during over two years continuously, then analyze the data. From the analysis, we could measure the energy consumption profile of three kinds of sensor nodes. The experiment shows all kinds of nodes can operate over one year with two AA-size alkaline batteries. Using a measure of reliability of the monitoring system called 'deadzone', the system has showed the failure operation for 842 hours (4.66 %) during over 18,000 hours total operation period.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3064-3066
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• 1999

The existing equipment with wire communication can expect the stability of data transmission. However, according to increasing a number of DTE (Data Terminal Equipment), wiring work becomes a heavy burden. Restriction to application about portable DTE and the lack of flexibility are another drawback of wire communication. This paper presents the design and implementation of a RF (Radio Frequency) based wireless communication system. The RF based module is designed to the multi communication between DTEs. The RF based module consists of RF circuit and microprocessor. The main properties of RF circuit are maximum 5Kbps transmission rate, maximum 90m transmission distance and 433MHz frequency band. The microprocessor rearrange the data into AHDLC(Advanced High level Data Link Control) format and then instructs RF circuits to transmit/receive the data. The RF module have a wide application field such as fire/security alarm, remote control/measurement etc..

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.237-246
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• 2022

This paper proposes a method to adjust the turn ratio of a transformer for the high-efficiency operation of an LLC converter with a wide input range in a wired/wireless integrated charging system for electric vehicles. The characteristics of the inductive power transfer converter in the integrated charging system are analyzed to design the LLC converter, and the DC-link voltage range is derived. The aspect of voltage gain following each parameter of the LLC converter is analyzed, and the resonant network and transformer are designed. Based on the designed parameters, the feasibility of the design and control method is verified by implementing the operation of the LLC converter according to the DC-link and battery voltages.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.160-168
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• 2013

In tactical environment, tactical wireless networks are generally comprised of Tactical MANETs(T-MANETs) or Tactical WMNs(T-WMNs). The most important services in tactical network are voice and low rate data such as command control and situation awareness. These data should be forwarded via multi-hop in tactical wireless networks. Urgent and mission-critical data should be protected in this environment, so QoS(Quality of Service) must be guaranteed for specific type of traffic for satisfying the requirement of a user. In IEEE 802.11s, TDMA-based MAC protocol, MCCA(MCF Controlled Channel Access), has a function of resource reservation. But 802.11s protocol can not guarantee the end-to-end QoS, because it only supports reservation with neighbors. In this paper, we propose the routing protocol, R-HWMP(Reservation-based HWMP) which has the resource reservation to support the end-to-end QoS. The proposed protocol can reserve the channel slots and find optimal path in T-WMNs. We analyzed the performance of the proposed protocol and showed that end-to-end QoS is guaranteed using NS-2 simulation.