• Journal of the Korea Society of Computer and Information
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• v.22 no.1
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• pp.71-76
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• 2017

Recently, there are various researches using inaudible high frequencies like as wireless communication based smart devices, data transmission algorithm, indoor positioning trace technologies. However, when they use high frequencies of inaudible range, they have a problem that the accuracy of data transmission with high frequencies was low because of interference from ambient noise in our real life. To solve this problem, in this paper, we proposed an application based on smart phone and server system for collection of ambient noise and detection of robust high frequency range. The server system could detect the robust high frequency range from statistical analysis of collected noise and the robust high frequency could avoid interference from ambient noise. We tested the proposed application's ability to gather noise and high frequencies for a certain period of time to evaluate performance. According to the testing results, we confirmed that the proposed application and server system could detect a robust high-frequency range via noise analysis in real life. Therefore, the proposed application and server could be a useful technology for future research on inaudible high frequencies.

• Journal of the Korea Society of Computer and Information
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• v.20 no.8
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• pp.7-13
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• 2015

Recently, there are serviced user customized advertisement of various type using smart device. Representative services are advertisement service using light of smart TV screen or audible sound of smart TV to transmit advertisement information. However, those services have to do a specific action of smart device user for advertisement information or need audible audio information of TV contents. To overcome those weakness, therefore, we propose an advertisement method using inaudible sound of speaker based on smart device. This method supports the transfer of advertising content to the smart device user with no additional action or TV audio signal required to access that content. The proposed method used two high frequencies among 18kHz ~ 22kHz of audible frequency range which smart TV can send out. And it generates those frequencies synthesized with audio of TV contents as trigger signal which can send advertisements to smart device. Next, smart device analysis the trigger signal and request advertisement contents related to the signal to server. After then, smart device can show the downloaded contents to user. Because the proposed method uses the high frequencies of sound signals via the inner speaker of the smart device, its main advantage is that it does not affect the audio signal of TV content. To evaluate the efficacy of the proposed method, we developed an application to implement it and subsequently carried out an advertisement transmission experiment. The success rate of the transmission experiment was approximately 97%. Based on this result, we believe the proposed method will be a useful technique in introducing a customized user advertising service.

• Journal of the Korea Society of Computer and Information
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• v.22 no.11
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• pp.49-55
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• 2017

Recently, for safety of people, there are proposed so many technologies which detect density of people at the specific place or space. The representative technology for crowd density estimation was using image analysis method from CCTV images. However, this method had a weakness which could not be used and which's accuracy was lower at the dark or smog space. Therefore, in this paper, to solve this problem, we proposed a user density estimation system at closed space using high frequency and smart device. The system send inaudible high frequencies to smart devices and it count the smart devices which detect the high frequencies on the space. We tested real-time user density with the proposed system and ten smart devices to evaluate performance. According to the testing results, we confirmed that the proposed system's accuracy was 95% and it was very useful. Thus, because the proposed system could estimate about user density at specific space exactly, it could be useful technology for safety of people and measurement of space use state at indoor space.

• Journal of the Korea Society of Computer and Information
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• v.26 no.7
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• pp.57-64
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• 2021

In this paper, we propose and test the efficacy of an easy-to-use user location certification system for public places that relies on frequencies outside the audible range for humans. The inaudible frequencies come in signal frequency between 18-20 kHz and are generated by general audio speaker. After an individual's smart device detects the signal frequency, it sends the frequency value, user's personal ID, and user's location to a system server that certifies the user's visit location currently. The system server then saves a user visit record and categorizes it by individual. To show the usefulness of this proposed system, we developed a user visit certification application for smart devices linked to a system server. We then conducted a user visit certification experiment using the proposed system, with the result showing 99.6% accuracy. For a comparison, we then held a user visit certification experiment using a QR code, which confirmed that our proposed system performs better than QR code location certification. This proposed system can thus provide restaurants and other facilities reliable user contact tracing and electronic visitor access lists in the age of COVID-19.

• Journal of the Korea Society of Computer and Information
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• v.24 no.4
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• pp.99-105
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• 2019

Recently, many people enjoy movies and music content through their smart devices for using public transportation like as bus or subway. However, because their concentration is aimed at content on their smart devices, passengers sometimes forget to disembark and miss their destination stations. Therefore, in this paper, we propose a destination notification system for disembarking public transport using high frequencies based on the smart devices. We tested 1,000 times real-time destination notification to performance evaluate of the proposed application and service system. According to the test results, the proposed system showed 99.4% and 99.6% accuracy and we confirmed that it could be very useful. As such, the proposed system could be a useful technology for notifying smart device users when to get off public transport, capable of global commercialization.

• Journal of the Korea Society of Computer and Information
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• v.20 no.8
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• pp.61-67
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• 2015

The existing methods for control between smart devices in near used Bluetooth, WiFi-Direct, or socket communication using Wi-Fi. However, those have a problem that can not use when operating system of each smart devices is different or when socket server is not working. In this paper, we proposed a new near control technology using High frequencies in audible frequency between smart devices to supplement the problem of existing methods. High frequencies use micro-phone and speaker of smart device and are a control signals that is combined high frequencies within 18kHz ~ 22kHz among audible frequency range. The proposed technology using High frequencies do not need any extra communication modules or socket servers and can use the most smart devices without operating system of devices. To evaluate the performance of the proposed technology, we developed a music play and music control application applied the proposed technology and tested a control experiment using the developed applications. The control success rate was 97% and recognition rate of surrounding people about using high frequencies was under 5%. Therefore, the proposed technology will be the useful technology to control between smart devices in near.

• Journal of the Korea Society of Computer and Information
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• v.20 no.12
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• pp.83-90
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• 2015

In this paper, we propose a new method for multi transmission method of data among near smart devices. Existing methods require the use of an extra application service where the operating system differs between smart devices. In contrast, the proposed method makes use of the smart device's inner speaker and microphone to confirm the transmission signal. Then, real sharing data is transmitted via WiFi or LTE. Therefore, the proposed method overcomes operating system issues with existing methods. Besides, BUMP technology works in a similar way to the method we propose, it only supports one-to-one transmission. To evaluate the efficacy of the new method, we tested one-to-many data transmission in an experiment: the results showed a 96% success rate. As a result, we believe that the proposed method is an effective multi transmission method of data among near smart devices.

• Annual Conference of KIPS
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• 2015.10a
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• pp.341-342
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• 2015

무선통신기술은 연결 중심의 IoT 시대에서 중요한 역할을 하고 있다. IoT 기기 간 데이터 통신을 위해 Bluetooth, NFC와 같은 기술이 활용되지만, 호환성의 문제가 있다. 비가청주파수를 활용한 데이터 통신 연구는 기존의 무선통신기술이 가지는 모듈 의존성, OS 종속성 문제를 해결하였다. 하지만 기존 연구 결과는 소량 데이터만 전송 가능하고, 데이터 전송량을 늘릴 경우 전송시간 대비 효율이 낮았다. 본 논문에서는 비가청주파수를 활용하여 대량의 비트를 여러 개의 프레임으로 나누어 연속적으로 전송하기 위한 통신 프로토콜을 제안한다. 이는 소량 데이터를 전송하는 기존 연구 결과의 높은 정확도와 함께 송신부와 수신부의 유기적인 상호작용을 통해 대량의 데이터 전송에 적합한 알고리즘이다.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.9
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• pp.321-326
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• 2015

In this paper, we proposed an algorithm which could transmit reliable data between smart devices by using inaudible high frequency of audible frequency range and cyclic redundancy check method. The proposed method uses 18 kHz~22 kHz as high frequency which inner speaker of smart device can make a sound in audible frequency range (20 Hz~22 kHz). To increase transmission quantity of data, we send mixed various frequencies at high frequency range 1 (18.0 kHz~21.2 kHz). At the same time, to increase accuracy of transmission data, we send some mixed frequencies at high frequency range 2 (21.2 kHz~22.0 kHz) as checksum. We did experiments about data transmission between smart devices by using the proposed method to confirm data transmission speed and accuracy of the proposed method. From the experiments, we showed that the proposed method could transmit 32 bits data in 235 ms, the transmission success rate was 99.47%, and error detection by using cyclic redundancy check was 0.53%. Therefore, the proposed method will be a useful for wireless transmission technology between smart devices.