• Journal of Internet Computing and Services
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• v.21 no.2
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• pp.19-26
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• 2020

This paper analyses the feasibility of using implantable antennas to detect and monitor tumors. We analyze this setting according to the wireless propagation loss and signal fading produced by human bodies and their environment in an indoor scenario. The study is based on the ITU-R propagation recommendations and prediction models for the planning of indoor radio communication systems and radio local area networks in the frequency range of 300 MHz to 100 GHz. We conduct primary estimations on 915 MHz and 2.4 GHz operating frequencies. The path loss presented in most short-range wireless implant devices does not take into account the human body as a channel itself, which causes additional losses to wireless designs. In this paper, we examine the propagation through the human body, including losses taken from bones, muscles, fat, and clothes, which results in a more accurate characterization and estimation of the channel. The results obtained from our simulation indicates a variation of the return loss of the spiral antenna when a tumor is located near the implant. This knowledge can be applied in medical detection, and monitoring of early tumors, by analyzing the electromagnetic field behavior of the implant. The tumor was modeled under CST Microwave Studio, using Wisconsin Diagnosis Breast Cancer Dataset. Features like the radius, texture, perimeter, area, and smoothness of the tumor are included along with their label data to determine whether the external shape has malignant or benign physiognomies. An explanation of the feasibility of the system deployment and technical recommendations to avoid interference is also described.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.932-940
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• 2005

In this paper, a planar half-circle shape ultra-wideband(UWB) antenna fed by CPW is designed, fabricated and measured for UWB communications. Within the UWB band(3.1 GHz${\~}$10.6 GHz), 5.15 GHz${\~}$5.825 GHz frequency band is used by IEEE 802.1la WLAN applications. It may be necessary to notch out this band to avoid interference with IEEE 802.1la WLAN. Therefore, we have proposed three kinds of UWB antennas having a notch function, such as a rectangular slot, a hat-shaped slot a circle-shaped slot. The notch frequency of the proposed antenna can be adjusted by controlling the slot length or slot width. From the measured results, the proposed antennas show a good gain flatness except the IEEE 802.1la WLAN frequency band and have a reasonable agreement with simulated results.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.79-86
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• 2007

In order to operate Low Earth Orbit(LEO) satellite on space, technical requirements and administrative procedure which are defined by the International Telecommunication Union(ITU) should be followed on satellite development. Main technical requirements to follow are purpose of use, bandwidth, Radio Frequency(RF) intensity, and constraints on new satellite network about existing satellite networks according to frequency spectrum. Such ITU's requirements are reflected and designed on system specification and space to ground interface control document. In order to have a right and protection about using the satellite network on space, the satellite network has to be registered on Master International Frequency Register(MIFR) and procedure for this has to be followed. Coordination with countries raising objection is needed in order to register. And reference and method for coordination are also needed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.341-350
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• 2007

In this paper, the derivation of protection ratio is newly proposed for the detailed planning of frequency coordination in microwave relay networks, and computed results for protection ratio of co-channel and adjacent channel are illustrated over the actual system and its frequency. It is shown that the suggested method based upon availability prediction can be expressed in terms of composite fade margin, interference-to-noise ratio(I/N), net filter discrimination, and system parameters. According to results, for 6.7 GHz, 60 km, 64-QAM, and I/N= -6 dB at BER $10^{-6}$, composite fade margin and co-channel protection ratio provide 25.5 and 50.7 dB, respectively. Also, net filter discrimination and adjacent channel protection ratio are obtained as 26.3 and 24.4 dB, respectively, at the first adjacent channel of 40 MHz. The proposed method provides some merits in computing protection ratio for microwave relay networks in view of an easy extension and practical applications considering more detailed and various system parameters.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.8-16
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• 2010

An orthogonal frequency division multiplexing (OFDM) system is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarriers. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. However, in the radio systems the distortion introduced by high power amplifiers (HPA's) such as traveling wave tube amplifier (TWTA) considered in this paper, is also critical. Since the signal amplitude of the OFDM system is Rayleigh-distributed, the performance of the OFDM system is significantly degraded by the nonlinearity of the HPA in the OFDM transmitter. In this paper, we propose a simplicial canonical piecewise-linear (SCPWL) model based digital predistorter to compensate for nonlinear distortion introduced by an HPA in an OFDM system. Computer simulation is carried on an OFDM system under additive white Gaussian noise (AWGN) channels with 16-QAM and 64-QAM modulation schemes and modulator/demodulator implemented with 1024-point FFT/IFFT. The simulation results demonstrate that the proposed predistorter achieves significant performance improvement by effectively compensating for the nonlinearity introduced by the HPA.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1373-1379
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• 2012

The interaction of magnetic field in the frequency range of 9~150 kHz radiating from a railway system with wireless systems has been the cause of radio frequency interference. In this paper, the equivalent circuit model of the RFI noise is proposed through source and transfer path analysis, and it is confirmed that the switching noise of several kHz that occurs a vehicle traction drive system and a substation is radiated by forming the loop circuit with a feeder line by a rolling stock. And the validity of the proposed equivalent circuit model is verified by analyzing the effects of RC banks installed in the real railway between Guri and Guksu stations, the RFI noise can be effectively mitigated by loading suitable capacitance between rail and feeding line.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.81-89
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• 2022

This study measured the radio environment of 10 domestic institutions with CubeSat ground stations for 24 hours in three frequency bands (VHF/UHF/S-band) allocated by the International Telecommunication Union (ITU). The impact of the RF environment around the ground stations on CubeSat downlink frequencies was analysed and compared with acceptable interference noise requirements from the CubeSat RF link. The findings indicate that not only the selection of downlink frequency but also the configuration of RF communication link design and ground station system of CubeSat should consider the S-band RF environment around the ground station due to the presence of several wireless devices.

• International Journal of Computer Science & Network Security
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• v.24 no.4
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• pp.206-210
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• 2024

Industrial facilities that use modern IT technologies require the ensured reliability and security of information in automated enterprise management. Concurrently, so as to ensure a high quality of communication, it is necessary to expand the bandwidth of communication channels, which are limited by the physical parameters of the radio frequency spectrum. In order to overcome this contradiction, we propose the application of technology fundamental to ultra-wideband signals, in which the ratio between the bandwidth and its central part is greater than "one". For this reason, the information signal is emitted without a carrier frequency - simultaneously within the entire frequency band - provided that the signal level is lower than the noise level. For the transmission of information content, the method of positional-time coding is used, in which each information bit is encoded by hundreds of ultrashort pulses that arrive within a certain sequence. Mathematical models of signals and values observed in wireless communication systems with autocorrelation reception of modulated ultra-wideband signals are furthermore recommended. These assist in identifying features of the dependence of the error probability on the normalized signal-to-noise ratio and the signal base. Comparative analysis has shown that the best noise immunity of the systems considered in this paper is the communication system, which uses the time separation of the reference and information signals. During the first half of the bit interval, the switch closes the output of the transmitter directly to the generator of the ultra-wideband signal - forming a reference signal. In the middle of the bit interval, the switch alternates the output to one of two possible positions depending on the encoding signal - "zero" or "one", forming the information part of the ultra-wideband signal. It should also be noted that systems with autocorrelation reception and separate transmission of reference and information signals, provide a high level of structural signal secrecy. Furthermore, they provide the reliable transmission of digital information, especially in interference conditions.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.17-24
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• 2009

This paper deals with the cancellation performance of loop back interference signal in the case of multihop relay of 16-QAM received signal at the USN radio network. For this, it is necessary to the exchange of information with long distance located station by means of the relay function between the node in the USN environment. In the relay node, the loop-back interference signal which the retransmitting signal is feedback to the receiver side due to the antenna of transmitter and receiver are co-used or very colsely located or using the nonlinear device. Due to this signal, the performance of USN system are degraded which are using the limited resource of frequency and power. For improve this, it is necessary to applying the adaptive signal processing algorithm in order to cancellating the unwanted loop-back interference signal at the frontend of receiver in relaying node, we can get the better system and multi hop performance. In the adaptive signal processing, we considered the 16-QAM signal which has a good spectral efficiency, firstly, than, the QR-Array RLS algorithm was used that has a fairly good convergence property and the solving the finite length problem in the H/W implementation. Finaly, we confirmed that the good elimination performanc was confirmed by computer simulation in the learing cuved and received signal constellation compared to the conventional RLS.

• ETRI Journal
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• v.34 no.6
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• pp.911-921
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• 2012

In high-speed wireless communications, an analysis of the propagation characteristics is an important process. Information on the propagation characteristics suitable for each environment significantly helps in the design of mobile communications. This paper presents the analysis results of radio propagation characteristics in outdoor environments for a new mobile wireless system at 781 MHz. To avoid the interference of Korean DTV broadcasting, we measure the channel characteristics in urban, suburban, and rural areas on Jeju Island, Republic of Korea, using a channel sounder and $4{\times}4$ antenna. The path loss (PL) measurement results differ from those of existing propagation models by more than 10 dB. To analyze the frequency characteristics for Korean propagation environments, we derive various propagation characteristic parameters: PL, delay spread, angular spread, and K-factor. Finally, we verify the validity of the measurement results by comparing them with the actual measurement results and 3D ray-tracing simulation results.