• Journal of Advanced Navigation Technology
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• v.11 no.3
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• pp.239-251
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• 2007

This thesis is about the reduction of the power consumption in GPS embedded terminals with periodic position fix to improve the time delay of position determination. In order to improve time delay of position determination during the wireless terminal is powered on, it needs to be set such that it can be periodically recalibrated by the GPS and those recalibrated values need to be saved in the terminal's memory so that it can reduce the time delay from the request of location. By using the trace of the information that's been saved in the terminal's memory, it can be set so that it'll be easier to determine whether the wireless terminal has gone into buildings and have the capability of checking if it has gone into a specific building. Likewise, while the terminal is turned on, in order calibrate the location, it needs to continuously work the GPS engine which leads to a rapid decrease in terminal's idle time. This thesis proposes some solutions regarding these issues - reducing 20 ~ 30% of the battery consumption for GPS visible situation that can occur when the wireless terminal periodically calibrates its location to determine the in-building status, and extending the idle time of the terminal by flexibly using the suggested GPS calibration time method according to wireless terminal's mobility.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.4
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• pp.207-212
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• 2015

Wi-Fi Direct allows battery powered mobile devices to form a wireless ad hoc network. Since one member of the network called Group Owner (GO) takes the role of managing the network, the network lifetime is mainly affected by the energy efficiency of GO. Hence, Wi-Fi Direct defines power saving schemes that allow GO to save the energy by turning off its radio interface during the periods called absence periods. However, the Wi-Fi Direct specification does not specify how to set parameters (denoted by PS parameters) determining the schedule of the absence periods. In this paper, we therefore propose a novel traffic-aware power saving scheme for Wi-Fi Direct networks. In particular, the proposed scheme estimates the application-level traffic load and adaptively tunes the PS parameters according to the estimated value.

• Smart Structures and Systems
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• v.22 no.5
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• pp.509-525
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• 2018

Sensors and systems in Civionics technology play an important role for continuously facilitating real-time structure monitoring systems by detecting and locating damage to or degradation of structures. An advanced materials, design processes, long-term sensing ability of sensors, electromagnetic interference, sensor placement techniques, data acquisition and computation, temperature, harsh environments, and energy consumption are important issues related to sensors for structural health monitoring (SHM). This paper provides a comprehensive survey of various sensor technologies, sensor classes and sensor networks in Civionics research for existing SHM systems. The detailed classification of sensor categories, applications, networking features, ranges, sizes and energy consumptions are investigated, summarized, and tabulated along with corresponding key references. The current challenges facing typical sensors in Civionics research are illustrated with a brief discussion on the progress of SHM in future applications. The purpose of this review is to discuss all the types of sensors and systems used in SHM research to provide a sufficient background on the challenges and problems in optimizing design techniques and understanding infrastructure performance, behavior and current condition. It is observed that the most important factors determining the quality of sensors and systems and their reliability are the long-term sensing ability, data rate, types of processors, size, power consumption, operation frequency, etc. This review will hopefully lead to increased efforts toward the development of low-powered, highly efficient, high data rate, reliable sensors and systems for SHM.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.66-78
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• 2009

A mobile ultrasound scanner developed for use in point-of-care applications is introduced, which can not only provide ultrasound images but can also measure various bio-signals. The mobile ultrasound scanner is also designed to meet the demanding requirements for point-of-care diagnosis, such as battery-powered operation, portability in terms of size and weigh, and real-time wireless communications capability for remote diagnosis. To meet these requirements, an efficient beamforming method for high resolution imaging with a small number of active elements, a hardware efficient beamformer architecture, and echo processing algorithms with greatly reduced computational complexity have been developed. Experimental results show that the prototype mobile ultrasound scanner is fully functional and satisfies most of the design requirements.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1925_1926
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• 2009

This paper describes a novel power management circuitry for reducing the sleeping mode power dissipation. Based on the proposed power management circuitry, the sensor module can be activated by RF wake-up signal, perform designated process and deactivate itself. There is absolutely no power dissipation at the sleeping mode which takes almost time of the operation. The temperature sensor module using solar cell as energy source has been fabricated and tested. Experimental results show that the sensor module with 3300 ${\mu}$F for storage capacitor can transmits RF temperature data to a receiver at a distance of 20 m every 15 second in a normal indoor light condition and keep the capacitor voltage over 9 V. And the sensor module can operate 100 times with a single charging, that means it is possible for the sensor module to transmit every 5 minute for 8 hours without light or any other power input during the night time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.10 s.115
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• pp.997-1004
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• 2006

With the growth in electronics and the remarkable advance in wireless communication technology, mobile devices, such as mobile phones and PDAs are incessantly improved in their diverse functional performance. Lighter weight and smaller size has been gradually accomplished by recent circuit integration technology resulting in rapid growth in the number of mobile phone subscribers. Driven by customer demand, recent mobile devices are fully capable of realizing a variety of dazzling multimedia effects powered by electro-acoustic parts that have become one of the generic components. However, This paper also presents an oval micro-speaker, that is' expected to show an excellent performance within limited space of mobile phone, and its performance design has been suggested as well. Finally, a statistical approach to achieve high characteristic and performance is suggested by Taguchi method to identify a certain relationship between a mobile phone and a micro-speaker.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.167-170
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• 2011

많은 측위 알고리즘이 참조노드가 정사각형의 모서리에 위치한다고 가정 하고 있지만, 실제로는 다각형이 되거나 매쉬형으로 배치될 수 있다. 신호세기를 달리함으로써 동심원을 구성하여 측위하는 WMRL(Weighted Multiple Rings Localization)도 기본적으로 참조노드의 배치가 정사각형으로 가정하고 있다. 본 논문에서는 참조노드는 임의로 배치되어 있는 경우에서의 측위로 확장한다. 즉, 측위하는 센서 노드가 수신 가능한 전파를 송신하는 모든 참조노드로부터 링 번호를 기반으로 자신의 위치를 추청한다. WMRL의 다중 신호 세기 링 방식을 채용, 각 링의 도달거리를 기반으로 센서노드가 자신과 참조노드 간의 거리를 유추하고, 최소자승법을 이용해 자신의 좌표를 계산하는 알고리즘을 제안한다. 실험 결과 제안한 알고리즘은 에러가 없는 환경과 다수 참조노드 환경에서 WMRL 및 WCL(Weighted Centroid Localization)보다 2배 이상의 성능향상을 보였으며, 에러가 있는 전파환경에서는 DV-hop 보다 평균 6%, WCL 및 WMRL에는 평균 16% 정도의 성능 향상 결과를 보였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.493-496
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• 2005

With the growth in electronics and the remarkable advance in wireless communication technology, mobile devices, such as mobile phones and PDAs are incessantly improved in their diverse functional performance. Lighter weight and smaller size has been gradually accomplished by recent circuit integration technology resulting in rapid growth in the number of mobile phone subscribers. Driven by customer demand, recent mobile devices are fully capable of realizing a variety of dazzling multimedia effects powered by electro-acoustic parts that have become one of the generic components. However, this paper also presents an oval micro-speaker, that is expected to show an excellent performance within limited space of mobile phone, and its performance design has been suggested as well. Finally, a statistical approach to achieve high characteristic and performance is suggested by Taguchi method to identify a certain relationship between a mobile phone and a micro-speaker.

• Annual Conference of KIPS
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• 2019.10a
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• pp.329-330
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• 2019

무선 센서 네트워크(WSN)는 배터리 자원의 제약으로 인해 수명이 짧다는 문제와 많은 이웃 노드와 통신하는 노드의 에너지 소비가 증가하는 에너지 불균형 문제를 가지고 있다. 이를 해결하고자, 최근에는 태양 에너지 수집형 노드를 사용하여 에너지를 지속적으로 수집함으로써 배터리 자원 제약 문제를 해결하려는 연구들이 활발히 진행되고 있다. 기존의 배터리 기반의 WSN을 위하여 제안된 유명한 데이터 수집 기법인 CTP(Collection Tree Protocol)도 이와 같은 에너지 제약 및 에너지 사용 불균형 문제는 고려하지 않고 설계되었다. 따라서 정전 노드 발생 및 루프 발생과 같은 네트워크의 안정성이 심각하게 저하되는 문제를 내포하고 있었다. 이를 해결하고자, 본 논문에서는 태양 에너지 수집형 노드로 구성된 WSN을 위한 향상된 CTP 기법(Solar-CTP)을 제안한다. 제안된 Solar-CTP기법에서는 수집 에너지 및 사용 에너지양 예측을 통해 노드 동작 모드를 결정한다. 성능 검증을 통해 기존 CTP에 비해 Solar-CTP의 정전 노드의 수가 매우 적고, 싱크의 데이터 수집량이 많아진 것을 확인하였다.

• International Journal of Computer Science & Network Security
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• v.21 no.9
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• pp.275-280
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• 2021

With the development of communication networks, the processes of exchanging and transmitting information rapidly developed. As millions of images are sent via social media every day, also wireless sensor networks are now used in all applications to capture images such as those used in traffic lights, roads and malls. Therefore, there is a need to reduce the size of these images while maintaining an acceptable degree of quality. In this paper, we use Python software to apply K-mean Clustering algorithm to compress RGB images. The PSNR, MSE, and SSIM are utilized to measure the image quality after image compression. The results of compression reduced the image size to nearly half the size of the original images using k = 64. In the SSIM measure, the higher the K, the greater the similarity between the two images which is a good indicator to a significant reduction in image size. Our proposed compression technique powered by the K-Mean clustering algorithm is useful for compressing images and reducing the size of images.