• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.45-50
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• 2005

This paper make an analysis of UWB Communication System. In case endoscope, medical equipment, is applied to UWB, We could study through body-channel that frequency transmitted of received signal is differ from wireless in the existing air. It suggested TR-UWB form, non-coherent received method in dispersion-medium like humans bodies by accomplishing ability analysis of BPM, TR, BER of Differential, UWB Communication modulation and demodulation form.

• ETRI Journal
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• v.37 no.6
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• pp.1055-1064
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• 2015

We demonstrate a next-generation high-capacity mobile fronthaul based on radio over fiber (RoF) technology, which links between a digital unit and a radio unit supporting two frequency assignments and $2{\times}2$ multiple input, multiple output antennas. To confirm the technical feasibility of a mobile fronthaul, we experimentally investigate its down- and uplink end-to-end performances including the optical and radio frequency (RF) signal path. Frequency-dependent performance deviations, error vector magnitude variations, overall system performance variations caused by optical to electrical conversion, and intermediate frequency to RF conversions are examined. Experimental verifications on multiple LTE uplink signals are performed for the first time. We also demonstrate several commercial mobile Internet services, YouTube video streaming, and file transfers using off-the-shelf mobile devices, through a mobile fronthaul based on RoF.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.11
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• pp.2992-3007
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• 2012

Recently there has been an increasing interest in exploring the radio irregularity research problem in Wireless Sensor Networks (WSNs). Measurements on real test-beds provide insights and fundamental information for a radio irregularity model. In our previous work "LMAT", we solved the path planning problem of the mobile anchor node without taking into account the radio irregularity model. This paper further studies how the localization performance is affected by radio irregularity. There is high probability that unknown nodes cannot receive sufficient location messages under the radio irregularity model. Therefore, we dynamically adjust the anchor node's radio range to guarantee that all the unknown nodes can receive sufficient localization information. In order to improve localization accuracy, we propose a new 2-hop localization scheme. Furthermore, we point out the relationship between degree of irregularity (DOI) and communication distance, and the impact of radio irregularity on message receiving probability. Finally, simulations show that, compared with 1-hop localization scheme, the 2-hop localization scheme with the radio irregularity model reduces the average localization error by about 20.51%.

• International journal of advanced smart convergence
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• v.12 no.1
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• pp.92-100
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• 2023

Wireless communication technology is becoming increasingly prevalent in smart factories, but the rise in the number of wireless devices can lead to interference in the ISM band and obstacles like metal blocks within the factory can weaken communication signals, creating radio shadow areas that impede information exchange. Consequently, accurately determining the radio communication coverage range is crucial. To address this issue, a Radio Environment Map (REM) can be used to provide information about the radio environment in a specific area. In this paper, a technique for estimating an indoor REM usinga mobile robot and machine learning methods is introduced. The mobile robot first collects and processes data, including the Received Signal Strength Indicator (RSSI) and location estimation. This data is then used to implement the REM through machine learning regression algorithms such as Extra Tree Regressor, Random Forest Regressor, and Decision Tree Regressor. Furthermore, the numerical and visual performance of REM for each model can be assessed in terms of R2 and Root Mean Square Error (RMSE).

• ETRI Journal
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• v.27 no.1
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• pp.43-52
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• 2005

In this paper, we introduce an adaptive radio resource allocation for IP-based mobile satellite services. We also present a synchronous multibeam CDMA satellite system using an orthogonal resource sharing mechanism among downlink beams for the adaptive packet transmission. The simulation results, using a Ka-band mobile satellite channel and various packet scheduling schemes, show that the proposed system and resource allocation scheme improves the beam throughput by more than two times over conventional systems. The simulation results also show that, in multibeam satellite systems, a system-level adaptation to a user's channel and interference conditions according to user locations and current packet traffic is more efficient in terms of throughput improvement than a user-level adaptation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1546-1553
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• 1996

The bit error probability of RS/trellis concatenated coded-modualtion system in the mobile radio channel is analyzed. A new upper bound to the symbol error probability of the inner TCM in the mobile radio channel is obtained by exploiting the unequal symbol error probability of the TCM. This bound is applied to the derivation of the upper bound to the bit error probability of the concatenated coded-modulation system. An efficient way of searching distance spectrum of the TCM in mobile radio channel is devised. Our new bounds are tighter than the earlier studied other bounds.

• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.167-172
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• 2015

Research results on possible effects caused by radiofrequency fields in children are limited because most of the studies published so far have focused on adults, rather than children. Mobile phone use is now widespread, even among younger children. If a biological risk due to mobile phone exposure is found, it might be greater in children because their bodies might be more sensitive to radiofrequency energy. The issue of a possible difference in sensitivity between adults and children begins with whether any difference exists physically in terms of electromagnetic absorption. This paper presents a review of recent publications on dosimetric comparisons between children and adults with respect to radiation from mobile phones. The issue of the health effects of mobile phone use is beyond the scope of the present review. Most of the dosimetry research on possible differences in power absorption between children and adults has been based on numerical modeling and analysis. The understanding of the results so far is presented and needed studies are described.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.560-564
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• 2003

In this paper, we carried out performance analysis of mobile station with built-in antenna for PCS(Personal Communication System) band. The radiation patterns for antenna and mobile phone were simulated by using 3D simulation program, HFSS(High Frequency Structure Simulator) and SEMCAD(Simulation Platform for Electromagnetic Compatibility Antenna Design Dosimetry). We observed radiation pattern variation according to installation of LED(Light Emitting Diode) circuit and ground pattern. The radiation pattern of prototype mobile phone was measured, and the radio sensitivity was measured by using Agilent E5515C and chamber. The measured maximum antenna gain at 1.87GHz was 0.21dBi. The measured radio sensitivity of prototype mobile phone shows proper performances comparable to other models with external antennas.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.361-364
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• 2011

Nowadays, an explosive increase of mobile devices has triggered a lot of research into radio resource management. Therefore, many studies have been done and still underway to use this limited resource efficiently. However, most of the existing studies focused on efficiency in mac layer. In this paper, I proposed a timer to manage radio resource, which refreshes the timer's values based on the number of connections dynamically. This dynamic timer enables Base Station (BS) to be able to manage available radio resources efficiently and accommodate much more Mobile Stations (MSs). Simulation result showed that BS with dynamic timer could accommodate the MS about 30% more, compared with BS with a static timer in terms of radio resource management. Dynamic timer is not restricted to any specific network standard. So its mechanism is practical and implementable without changing the original standard, which can contribute to service providers by increasing capability that BS can support.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.58-63
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• 2013

Since radio interference can degrade the performance of systems or limit the system operation, an accurate assessment of radio interference with the existing systems should be conducted prior to the operation of a new system. In this paper, we present an evaluation methodology for the radio interference between radio-navigation satellite service (RNSS) systems and mobile communication service (MS) system. Radio interferences from RNSS systems into MS system using minimum coupling loss (MCL) method are simulated and vice-versa, and the frequency sharing condition between two systems are derived in a same geographical area.