• International Journal of Advanced Culture Technology
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• 제5권2호
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• pp.54-62
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• 2017

Currently, falling to industrial field workers is causing serious injuries. Therefore, many researchers are actively studying the fall by using acceleration sensor, gyro sensor, pressure sensor and image information.Also, as the spread of smartphones becomes common, techniques for determining the fall by using an acceleration sensor built in a smartphone are being studied. The proposed method has complexity due to fusion of various sensor data and it is still insufficient to develop practical application. Therefore, in this paper, we use acceleration sensor module built in smartphone to collect acceleration data, propose a simple falling algorithm based on accelerometer sensor data after normalization and preprocessing, and implement an Android based app.

• International journal of advanced smart convergence
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• 제10권3호
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• pp.10-16
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• 2021

In this paper, we devise a Shapley-value-based covert channel in smartphones. More specifically, unlike ordinary use of Shapley value in cooperative game, we make use of a series of Shapley values, which are computed from sensor data collected from smartphones, in order to create a covert channel between encoding smartphone and decoding smartphone. To the best of our knowledge, we are the first to contrive covert channel based on Shapley values. We evaluate the encoding process of our proposed covert channel through simulation and present our evaluation results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권12호
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• pp.5805-5825
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• 2019

Smartphones are important platforms because of their sophisticated computation, communication, and sensing capabilities, which enable a variety of applications in the Internet of Things (IoT) systems. Moreover, advancements in hardware have enabled sensors on smartphones such as environmental and chemical sensors that make sensor data collection readily accessible for a wide range of applications. However, dynamic, opportunistic, and heterogeneous mobility patterns of smartphone users that vary throughout the day, which greatly affects the efficacy of sensor data collection. Therefore, it is necessary to consider phone users mobility patterns to design data collection schedules that can reduce the loss of sensor data. In this paper, we propose a mobility-based weighted adaptive opportunistic scheduling framework that can adaptively adjust to the dynamic, opportunistic, and heterogeneous mobility patterns of smartphone users and provide prioritized scheduling based on various application scenarios, such as velocity, region of interest, and sensor type. The performance of the proposed framework is compared with other scheduling frameworks in various heterogeneous smartphone user mobility scenarios. Simulation results show that the proposed scheduling improves the transmission rate by 8 percent and can also improve the collection of higher-priority sensor data compared with other scheduling approaches.

• 정보보호학회논문지
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• 제25권6호
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• pp.1477-1484
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• 2015

스마트폰 기반 금융 산업의 발달로 스마트폰을 이용한 인증 기법에 관심이 높아지고 있다. 다양한 생체 기반 사용자 인증 방식이 존재하지만 아직까지 스마트폰 기반 사용자의 걸음 패턴(gait) 인증 방식은 뚜렷한 발전을 보이고 있지 않다. 본 논문에서는 스마트폰에 기본적으로 탑재된 가속도 센서를 이용해 사용자를 인증하는 방법을 제안한다. 구체적으로, 스마트폰에서 수집한 데이터를 3D 변환하여 자세를 교정하고, 변환된 데이터에서 특징을 추출한 뒤 주성분 분석, 가우시안 혼합 모델링 과정을 거쳐 데이터를 학습 시킨다. 다음으로, 신뢰구간 검증 방식을 사용해 사용자 데이터를 검증했다. 그 결과, 통제 요인과 한계점이 많았던 선행 가속도 연구들과 달리 최소한의 통제 요인과 높은 정확도(약 96%)로 사용자 인증이 가능함을 입증했다.

• 한국멀티미디어학회논문지
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• 제17권12호
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• pp.1437-1445
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• 2014

A smartphone has very limited input methods regardless of its various functions. In this respect, it is one alternative that sensor motion recognition can make intuitive and various user interface. In this paper, we recognize user's motion using acceleration sensor, magnetic field sensor, and gyro sensor in smartphone. We try to reduce sensing error by gradient descent algorithm because in single sensor it is hard to obtain correct data. And we apply vector quantization by conversion of rotation displacement to spherical coordinate system for elevated recognition rate and recognition of small motion. After vector quantization process, we recognize motion using HMM(Hidden Markov Model).

• International Journal of Advanced Culture Technology
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• 제4권1호
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• pp.28-30
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• 2016

Due to the high increment in usage and built-in advanced technology of smartphones, human activity recognition relying on smartphone sensor data has become a focused research area. In order to reduce noise of collected data, most of previous studies assume that smartphones are fixed at certain positions. This strategy is impractical for real life applications. To overcome this issue, we here investigate a framework that allows detecting the status of a traveller as idle or moving regardless the position and the direction of smartphones. The application of our work is to estimate the total energy consumption of a traveller during a trip. A number of experiments have been carried out to show the effectiveness of our framework when travellers are not only walking but also using primitive vehicles like motorbikes.

• 대한안전경영과학회지
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• 제21권4호
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• pp.59-65
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• 2019

The Location Based Service is growing rapidly nowadays due to the universalization of the use for smartphone, therefore the location determination technology has been placed in an important position. This study suggests a method that can provide the estimate of users' location by using PDR method and smartphone geomagnetic sensor data. This method assists the measure of enhancing the accuracy of indoor localization. Moreover, it is to study ways to provide the exact indoor layout for evacuating the workers in emergency such as fires and natural disasters.

• 한국전기전자재료학회논문지
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• 제35권5호
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• pp.459-465
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• 2022

This paper reports a method to use a wireless sensor network deployed in the field to real-time monitor soil moisture, warning when the moisture level reaches a specific value, and wirelessly controlling an additional device (LED or water supply system, etc.). In addition, we report all processes related to wireless irrigation system, including field deployment of sensors, real-time monitoring using a smartphone, data calibration, and control of additional devices deployed in the field by smartphone. A commercially available open-source Internet of Things (IoT) platform, NodeMCU, was used, which was combined with a 9V battery, LED and soil humidity sensor to be integrated into a portable prototype. The IoT-based soil humidity sensor prototype deployed in the field was installed next to a tree for on-site demonstration for the measurement of soil humidity in real-time for about 30 hours, and the measured data was successfully transmitted to a smartphone via Wifi. The measurement data were automatically transmitted via e-mail in the form of a text file, stored on the web, followed by analyses and calibrations. The user can check the humidity of the soil real-time through a personal smartphone. When the humidity of a soil reached a specific value, an additional device, an LED device, placed in the field was successfully controlled through the smartphone. This LED can be easily replaced by other electronic devices such as water supplies, which can also be controlled by smartphones. These results show that farmers can not only monitor the condition of the field real-time through a sensor monitoring system manufactured simply at a low cost but also control additional devices such as irrigation facilities from a distance, thereby reducing unnecessary energy consumption and helping improve agricultural productivity.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.4021-4030
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• 2015

맥파는 심전도와 같이 자율신경계를 통해 생리적 반응을 측정하는 신호이지만, 손가락에 센서 하나만 부착시키면 되기 때문에 상대적으로 신호의 측정이 간편하다는 장점을 가지고 있어 u-Healthcare 분야에서의 활용이 용이하다. 따라서 본 연구의 목적은 스마트폰 카메라의 CMOS 영상 센서를 활용하여 맥파를 비침습적으로 측정하는 방법 중의 하나인 광용적맥파를 획득하고 이로부터 스트레스 여부를 판단하는 휴대형 시스템을 개발하여 u-Healthcare 분야에서의 활용 가능성을 확인하는 것이다. 이를 위해 광용적맥파를 별도의 센서에 의한 측정이 아닌 스마트폰 카메라에서 획득되는 영상 데이터를 활용하여 광용적맥파를 획득한 후 분석하였다. 또한 확보된 광용적맥파 영상신호 데이터를 이용하여 심박변이도와 스트레스 지수를 별도의 호스트 장비 없이 스마트폰만을 이용해 사용자에게 제공 하였다. 또한 부가적으로 스마트폰에 부착가능한 별도의 하드웨어 디바이스를 개발함으로써 획득된 데이터의 신뢰도 및 정확성을 향상시켰다. 실험결과를 통해 스마트폰의 카메라 영상을 활용하여 광용적맥파 신호를 통한 심박수 측정과 스트레스의 정도를 분석하기 위한 스트레스 지수 추출이 가능함을 확인할 수 있었다. 본 연구에서는 상용화된 제품 또는 정형화된 센서가 아닌 스마트폰의 카메라를 이용하기 때문에 상용화된 외부 센서에 의한 광용적맥파 신호보다는 해상도가 떨어지는 단점이 있음에도 불구하고 결과 데이터의 신뢰도 향상을 위한 별도의 추가외부 장치 개발 및 여러 가지 최적화 알고리즘을 통해 신뢰성 있는 데이터를 확보할 수 있어 u-Healthcare 장비로써의 활용 가능성을 확인할 수 있었다.

• International Journal of Advanced Culture Technology
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• 제5권2호
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• pp.63-73
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• 2017

In this paper, we propose algorithm for determining the static and dynamic posture using the acceleration sensor of smartphone. The measured acceleration values are then analyzed according to a preprocessing to the respective axis (X, Y, Z) and posture (standing, sitting, lying) presents static posture determination criterion. The proposed static posture determination condition is used for static posture determination and dynamic posture determination. The dynamic posture is determined by using regression linear equations. In addition, transition state can be grasped by SVM change in dynamic posture determination. Experimental results are presented using data and app. Experiments were performed using data collected from 10 adults.