• The KIPS Transactions:PartC
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• v.17C no.2
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• pp.215-222
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• 2010

IEEE 802.15 WPAN(Wireless personal area network) technologies represented by Bluetooth are prevalent these days. However, they have short radio coverage and thus cannot be used to build a SNS for servicing users spread over a wide area. In this paper, we develop a mobile SNS(Social Network System) that does not necessitate any infrastructure support using the Bluetooth technology and the mobility based information dissemination technique. Using so-called mobility assisted data dissemination technique we overcome the short radio range restriction of WPAN technologies. We develop Blue Market, a free online marketplace program, as a proof of concept.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.243-251
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• 2010

The military has been putting great efforts into applying data communication on existing voice communication systems being used in NCW(Network Centric Warfare). Data communication will be an effective choice in one of many effort to yield a minimum kill chain, comparing to legacy voice communications, when tactical units conduct their missions. However, the required budget will be enormous, in case of the replacement of a lot of legacy communication systems with new one. As a cost-effective alternative, the tactical data communication systems using the conventional radio systems instead of the development of new radio systems has been proposed. It is mandatory, though, to ensure QoS while maintaining data communication by making use of legacy radio systems already in use. This paper focuses on the performance issues experimented and analyzed for tactical data communication through the legacy radio systems as the first step towards guaranteed QoS. We have conducted various experiments such as the transmission error rate on certain tactical messages, performance evaluation of redundant transfers, the relationship between the transmission frame size and rate of error, the identification of error points in the transmission frame, and techniques to reduce the errors in both hopping and non-hopping modes. As a result of the performance experiments, The adaptive communication module which decides the redundant transmission or the Forward Error Correction(FEC) technique by analyzing channel status and current transmission status(hopping/non-hopping) of the legacy radio should be designed. the FEC technique in non-hopping, and the redundant transmission technique in hopping mode was recommended from the result of experiment with the frame size is 20bytes in non-hopping and 10Bytes frame size in hopping mode.

• Journal of the Institute of Convergence Signal Processing
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• v.17 no.2
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• pp.83-92
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• 2016

In this paper, we introduce the results of the testing and observation systems for performance wideband expansion in the Korean VLBI Network(KVN). The KVN performs VLBI observations to 1024 Mbps data rate, and 8192 Mbps observing for four simultaneous observation is now evaluating for normal operation. The VLBI stations in several world countries developed their own wideband observing systems to observe the celestial objects with high precision and high resolution or are working with several countries. The KVN is planning to introduce a high-speed sampler, OCTAD, for sampling directly up to 2048 MHz bandwidth for RF signal of K/Q/W/D band in the frequency band without conversion. Therefore, as a preliminary study for the performance scalability of the KVN then through the close cooperation with National Astronomical Observatory of Japan (NAOJ), the OCTAD high-speed sampler and OCTADISK2 high-speed recorder were installed in the KVN Yonsei station, and verify the performance through a wideband.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.736-743
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• 2016

In accordance with the trend of higher speed and automation, the Train Control System is building on the technology of control methods using radio in the technology of exchanging information by wire, toward a wireless communication method that will be applied using LTE-R radio communication technology with $4^{th}$ generation LTE mobile communication a $2^{nd}$ generation GSM-R. Therefore, a standard specification suitable for the Korea Radio based Train Control System-2(below KRTCS-2) for the 350km/h class using wireless communication is created; a prototype based on the standard specification is installed on a high-speed train and is installed on a test section(Ik san-Jeong eup) on the Honam high speed line to ensure the reliability and safety of the standard specifications, which are verified through various performance tests. In the future, the standard specification that has been established as a national railway standard, and the standard specifications will be commercialized by applying the train control system to conventional and High speed railway lines.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.10
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• pp.31-38
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• 2008

This paper describes sensor network system implementation for the IEEE 1451.2 standard which guarantees compatibilities between various wired sensors. The proposed system consists of the Network Capable Application Processor(NCAP) in the IEEE 1451.0, the Transducer Independent Interface(TII) in the IEEE 1451.2, the Transducer Electronic Data Sheet(TEDS) and sensors. The research goal of this study is to minimize and optimize system complexity for IC design. The NCAP is implemented using C language in personal computer environment. TII is used in the parallel port between PC and an FPGA application board. Transducer is implemented using Verilog on the FPGA application board. We verified the proposed system architecture based on the standards.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.295-302
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• 2011

Ubiquitous is an information communication environment which peoples could connect on network without being conscious of the network and computer condition at anytime and anywhere. Presently, advanced technology, digital cities and eco-friendly cities using Ubiquitous technology are being focused through out the world. As recent information industry and communication technology have developed remarkably, studies on intelligent structures and structural maintenance methods by combining a general idea of connecting all objects on network by interpolating computers which is called Ubiquitous Computing, and USN(Ubiquitous Sensor Network) are being attempted. In this paper, a basic experiment on penetration of RF(Radio Frequency) sensor nodes using an experimental sample setting concrete and reinforcing bar as variables is studied to estimate the possibility of applying wireless sensor networks in structures. The spring of reinforcing bars, concrete thickness, intensity of radio frequency were set up as variables, transmitting and receiving distance were checked vertically and horizontally. Moreover, Spectrum Analyzer was used for checking the magnitude of the frequency used in order to measure the reduction of radio wave exactly. The radio wave reduction was numerically analyzed, and the influence of the wavelength was analysed as well. As a result, the penetration depth in concrete without reinforcing bars was 45cm, and in reinforced concretes which reinforcing bars placed at spacing of 5cm and 15cm, the penetration depth were 37cm and 45cm each. No influence on radio wave penetration depth were found when the spacing of reinforcing bars in the reinforced concrete structures becomes over 15cm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.9
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• pp.1172-1179
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• 2020

With the establishment of the railway integrated radio network (LTE-R) environment, radio-based train control transmission and reception and various forms of service are provided. The smooth delivery of these services requires improved performance in a highly reliable and available wireless environment. This paper measured the LTE-R radio communication environment to improve radio communication performance of railway integrated wireless network reliability and availability, analyzed the results, and established the wireless environment model. Based on the built-up model, we also proposed an improved radio-access algorithm to control trains for improved reliability, suggesting a way to improve stability for handover that occur during open-air operation, and proposed an algorithm for frequency auto-heating to improve availability. For simulation, data were collected from the Korea Rail Network Authority (Daejeon), Manjong-Gangneung KTX route, which can measure the actual data of LTE-R wireless environment, and the results of the simulation show performance improvement through algorithm.

• Journal of Communications and Networks
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• v.11 no.2
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• pp.187-195
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• 2009

The application of mathematical analysis to the study of wireless ad hoc networks has met with limited success due to the complexity of mobility, traffic models and the dynamic topology. A scenario based universal mobile telecommunications system (UMTS) time division duplex (TDD) opportunistic cellular system with an ad hoc behaviour that operates over UMTS frequency division duplex (FDD) licensed cellular network is considered. In this paper, we present a new routing metric which overall improves system performance in terms of interference and routing which operate in an ad hoc network in an opportunistic manner. Therefore we develop a simulation tool that addresses the goal of analysis and assessment of UMTS TDD opportunistic radio system with ad hoc behavior in coexistence with a UMTS FDD primary cellular networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.2
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• pp.115-121
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• 2013

LED-ID (Light Emitting Diode-Identification) network is envisioned to be the next generation indoor wireless communication medium by which simultaneously high speed data transmission, identification, and illumination are possible. In spite of being extremely promising, it suffers from much impairment. Signals having different propagation paths can suffer from delays, and phase shifts which will eventually result interference. The probability of interference is also increased when communication links are established between a tag and several readers. Therefore it is necessary to reduce the interference in LED-ID network to ensure quality of service. It is possible to avoid interference by knowing the information about readers prior to assign the available spectrum. In this paper, we have proposed dynamic spectrum decision using cognitive radio concept. The simulation results justify that the proposed scheme is better than the conventional scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.7
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• pp.1214-1229
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• 2011

Power control is a key technique in spectrum underlay cognitive network to guarantee the interference temperature limit of the primary users (PUs) and the quality of service of the secondary users (SUs). In this paper, a robust power control scheme via link gain pricing with $H_{\infty}$ estimator is proposed. The scheme guarantees the interference temperature of the PUs through operating in the network-centric manner, and keeps the fairness between the SUs through link gain pricing. Furthermore, the $H_{\infty}$ filter is also used in the proposed scheme to estimate the channel variation, and thus the power control scheme is robust to the severe channel fading. Plenty of simulations are taken, and prove its superior robust performance against the channel fading, and its effectiveness in guaranteeing the interference temperature limit of the PUs.