• Smart Structures and Systems
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• v.14 no.4
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• pp.617-641
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• 2014

The energy constraint is still a common issue for the practical application of wireless sensors, since they are usually powered by batteries which limit their lifetime. In this paper, a practical compound energy efficiency strategy is proposed and realized in the implementation of a real time wireless sensor platform. The platform is intended for wireless structural monitoring applications and consists of three parts, wireless sensing unit, base station and data acquisition and configuration software running in a computer within the Matlab environment. The high energy efficiency of the wireless sensor platform is achieved by a proposed adaptive radio transmission power control algorithm, and some straightforward methods, including adopting low power ICs and high efficient power management circuits, low duty cycle radio polling and switching off radio between two adjacent data packets' transmission. The adaptive transmission power control algorithm is based on the statistical average of the path loss estimations using a moving average filter. The algorithm is implemented in the wireless node and relies on the received signal strength feedback piggybacked in the ACK packet from the base station node to estimate the path loss. Therefore, it does not need any control packet overheads. Several experiments are carried out to investigate the link quality of radio channels, validate and evaluate the proposed adaptive transmission power control algorithm, including static and dynamic experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3751-3774
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• 2014

With the rapid development of wireless communication, the confliction between the scarce frequency resources and the low spectral efficiency caused by the stationary spectrum sharing strategies seriously restricts the evolution of the future mobile communication. For this purpose, cognitive radio (CR) emerges as one of the most promising inventions which can overcome the spectrum shortage. As the key technology and main objective of CR, spectrum sharing can make full use of the limited spectrum, alleviate the scarcity of frequency resources and improve the system utilities, playing thereby an important role in improving the system performance of cognitive radio networks (CRNs). In this survey, the spectrum sharing in CRNs is discussed in terms of the sharing process, mainstream sharing technologies and spectrum sharing models. In particular, comparisons of different spectrum sharing strategies are concluded, as well as that of different spectrum sensing schemes in sharing procedure. Moreover, some application examples of the spectrum sharing in CRNs, such as smart grid, public safety, cellular network and medical body area networks are also introduced. In addition, our previous related works are presented and the open research issues in the field of spectrum sharing are stated as well.

• International journal of advanced smart convergence
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• v.10 no.1
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• pp.12-23
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• 2021

This paper proposes a low power radio frequency receiver front-end where, in a single stage, single-balanced mixer and voltage-controlled oscillator are stacked on top of low noise amplifier and re-use the dc current to reduce the power consumption. In the proposed topology, the voltage-controlled oscillator itself plays the dual role of oscillator and mixer by exploiting a series inductor-capacitor network. Using a 65 nm complementary metal oxide semiconductor technology, the proposed radio frequency front-end is designed and simulated. Oscillating at around 2.4 GHz frequency band, the voltage-controlled oscillator of the proposed radio frequency front-end achieves the phase noise of -72 dBc/Hz, -93 dBc/Hz, and -113 dBc/Hz at 10KHz, 100KHz, and 1 MHz offset frequency, respectively. The simulated voltage conversion gain is about 25 dB. The double-side band noise figure is -14.2 dB, -8.8 dB, and -7.3 dB at 100 KHz, 1 MHz and 10 MHz offset. The radio frequency front-end consumes only 96 ㎼ dc power from a 1-V supply.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4408-4428
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• 2019

Due to the rapid advancement in smart phones, numerous new specifications are developed for variety of applications ranging from health monitoring to navigations and tracking. The word indoor navigation means location identification, however, where GPS signals are not available, accurate indoor localization is a challenging task due to variation in the received signals which directly affect distance estimation process. This paper proposes a hybrid approach which integrates fingerprinting based K-Nearest Neighbors (K-NN) and lateration based MinMax position estimation technique. The novel idea behind this hybrid approach is to use Euclidian distance formulation for distance estimates instead of indoor radio channel modeling which is used to convert the received signal to distance estimates. Due to unpredictable behavior of the received signal, modeling indoor environment for distance estimates is a challenging task which ultimately results in distance estimation error and hence affects position estimation process. Our proposed idea is indoor position estimation technique using Bluetooth enabled smart phones which is independent of the radio channels. Experimental results conclude that, our proposed hybrid approach performs better in terms of mean error compared to Trilateration, MinMax, K-NN, and existing Hybrid approach.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.119-122
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• 2013

본 논문에서는 물품관리의 효율성을 위해 모바일 RFID리더기와 스마트 모바일 기기를 이용한 스마트 선반 시스템을 제안한다. 이 시스템을 사용하여 관리자는 물품에 부착되어진 태그를 읽어서 실시간으로 물품의 상세정보를 열람할 수 있고, 선반에 부착되어진 태그를 읽어서 물품의 재고나 위치오류 상태를 파악할 수 있다. 이는 각 선반마다 RFID리더기를 부착시킨 형태의 기존의 스마트선반 시스템과 유사한 기능을 수행하면서도 구축비용과 물품 재질에 따른 인식 오류의 해결부담을 줄일 수 있는 효과가 있다.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.236-244
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• 2007

The 40% scaled vehicle of Smart UAV has been developed for the investigation of basic flight characteristics and the verification of flight control algorithm. The similar gimbal hub and drive train with the full scale UAV were implemented and a forced air cooling reciprocating engine was installed. The various kind of tests were conducted for the major components of the vehicle. The important performance and mechanical endurance of the fabricated vehicle were identified by ground and hovering test.

• Journal of electromagnetic engineering and science
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• v.13 no.4
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• pp.208-213
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• 2013

This paper proposes a tag antenna for radio frequency identification (RFID) food system. The RFID tag antenna is designed and fabricated based on the rectangular loop concept used in the UHF band (Korean and Japanese standards, 916.7-923.5MHz). The proposed tag antenna is composed of a radiation patch, sensor tag chip, temperature sensor, oscillator, and battery. We conjugated matching between the tag antenna and the sensor tag using a U-shaped stub. Details of the proposed tag antenna design and the simulated and measured results are presented and discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.158-163
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• 2010

In this paper, we propose the location measurement algorithm of unknown tag based on RFID (Radio-Frequency IDentification) by using RSSI (Received Signal Strength Indication) and TDOA (Time Difference of Arrival) and extended Kalman filter in smart space. To do this, first, we recognize the location of unknown tag by using the RSSI and TDOA recognition methods. Second, we set the coordinate of the tag location measured by using trilateration and SX algorithm. But the tag location data measured by this method are included complex environmental error. So, we use the extended Kalman filter in order to revise error data of the tag location. Finally, we validate the applicability of the proposed method though the simulation in a complex environment.

• Journal of Broadcast Engineering
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• v.18 no.2
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• pp.237-248
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• 2013

Hybrid broadcasting environment is convergence of broadcasting and communication environment. In hybrid broadcasting environment, a number of media can be delivered using both broadcasting channel and other network unlike traditional broadcast environment that is able to deliver a couple of media by the limited bandwidth. Now, starting with smart TV, hybrid broadcasting environment combining broadcasting channel and IP network is established, and a variety of services are appearing. Moreover, the services using hybrid broadcasting environment are expected to appear soon for the other smart terminals such as smart phone and tablet PC. Scene composition is one of the methods that can consume effectively a number of media delivered from hybrid broadcasting environment. Using scene composition, multiple media can be consumed through the specified presentation time and space. Therefore, in this paper, it proposes the scene composition technology that is suitable for hybrid broadcasting environment and smart terminals. However, the spatial composition and temporal composition of media using script language and style language of HTML5 might increase the complexity of processing, and cause limitation of avaliable terminals. Also, a document of HTML5 can describe only one scene. By these reason, the proposed scene composition technology extends HTML5 in order to provide the spatial and temporal composition of media and description of multiple scene through markup language. In addition, it includes the extension of HTML5 in terms of utilization in hybrid broadcasting environment. For this proposal, this paper describes the technology of HTML5 and proposed scene composition. Also, it verifies the scene composition with both implementations and experiments.

• Journal of Information Processing Systems
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• v.7 no.1
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• pp.111-120
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• 2011

The concept of Smart-Homes is becoming more and more popular. It is anticipated that Radio Frequency IDentification (RFID) technology will play a major role in such environments. We can find many previously proposed schemes that focus solely on: authentication between the RFID tags and readers, and user privacy protection from malicious readers. There has also been much talk of a very popular RFID application: a refrigerator/bookshelf that can scan and list out the details of its items on its display screen. Realizing such an application is not as straight forward as it seems to be, especially in securely deploying such RFID-based applications in a smart home environment. Therefore this paper describes some of the RFID-based applications that are applicable to smart home environments. We then identify their related privacy and security threats and security requirements and also propose a secure approach, where RFID-tagged consumer items, RFID-reader enabled appliances (e.g., refrigerators), and RFID-based applications would securely interact among one another. At the moment our approach is just a conceptual idea, but it sheds light on very important security issues related to RFID-based applications that are beneficial for consumers.