• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.227-233
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• 2018

The purpose of satellite navigation meaconing jamming is to make the target GPS receiver calculate false navigation by meaconing the received satellite signals. At this time, since the received and transmitted signals have the same frequency, the back-lobe reduction level of antenna should be -160 dB when the Effective Radiated Power (ERP) is 1 Watt (30 dBm). Therefore, meaconing jamming is impossible by merely reducing the back-lobe level of antenna when the transmitter and receiver are in proximity to each other. In general, the transmitter and receiver are isolated by the time division method to eliminate such transmission/reception interference. This paper studied the optimal switching timing between transmitting and receiving when isolating the time division transmission and reception for GPS meaconing jamming.

• ETRI Journal
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• v.46 no.4
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• pp.619-632
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• 2024

Medical signal processing requires noise and interference-free inputs for precise segregation and classification operations. However, sensing and transmitting wireless media/devices generate noise that results in signal tampering in feature extractions. To address these issues, this article introduces a finite impulse response design based on a two-level transpose Vedic multiplier. The proposed architecture identifies the zero-noise impulse across the varying sensing intervals. In this process, the first level is the process of transpose array operations with equalization implemented to achieve zero noise at any sensed interval. This transpose occurs between successive array representations of the input with continuity. If the continuity is unavailable, then the noise interruption is considerable and results in signal tampering. The second level of the Vedic multiplier is to optimize the transpose speed for zero-noise segregation. This is performed independently for the zero- and nonzero-noise intervals. Finally, the finite impulse response is estimated as the sum of zero- and nonzero-noise inputs at any finite classification.

• The Journal of the Acoustical Society of Korea
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• v.23 no.4
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• pp.288-295
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• 2004

Detection and localization of a slow and quiet target in shallow water environments is a challenging problem for which it is well known that snapshot is deficient because of a fast and strong interferer. This paper presents waveguide interference filtering technique that mitigate strong interferer problems in adaptive matched field processing. MCM (multiple constraint method) based on NDC (null direction constraint) has been proposed for new spatial interferer filter. MCM-NDC using replica force a interferer component to be filtered through CSDM (cross-spectral density matrix). This filtering have an effect on sidelobe reduction and restoring of signal gain of a quiet target. This technique was applied to a simulation on Pekeris waveguide and vertical array data from MAPLE03 (matched acoustic properties and localization experiment) in the East Sea and was shown to improve SBNR (signal-to-background-and-noise ratio) over the standard MVDR (minimum-variance distortionless response) and NSP (null space projection) technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2B
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• pp.159-167
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• 2011

LTE-Advanced system requires uplink multi-antenna transmission in order to achieve the peak spectral efficiency of 15bps/Hz. In this paper, the uplink MIMO system model for the LTE-Advanced is proposed and an efficient link adaptation shceme using precoding is considered providing error rate reduction and system capacity enhancement. In particular, the proposed scheme determines a transmission rank by selecting the optimal wideband precoding matrix, which is based on the derived signal-to-interference and noise ratio (SINR) for the minimum mean squared error (MMSE) receivers of $2{\times}4$ multiple input multiple output (MIMO). The proposed scheme is verified by simulation with a practical MIMO channel model. The simulation results of average block-error-rate(BLER) reflect that the gain due to the proposed rank adapted transmission over full-rank transmission is evident particularly in the case of lower modulation and coding scheme (MCS) and high mobility, which means the severe channel fading environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2A
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• pp.83-94
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• 2012

Various wireless communication devices or network such as WRAN and WLAN will coexist in the TVWS(TV White Space). Because of this coexistence, the wireless devices which use the TVWS have to avoid interfering to not only licensed TV receiver and wireless microphone but also homogeneous or heterogeneous TVBD(TV Band Device)s. In this paper, we propose two frequency sharing methods for the coexistence of WLAN and WRAN in terms of interference reduction and throughput enhancement in both homogeneous and heterogeneous networks. One is the WRAN spectrum etiquette to provide more wide bandwidth for WLAN users and the other is the WLAN frequency selection methods to improve the throughput performance. The simulation results have confirmed the throughput improvement of the proposed methods. Moreover, the proposed methods is also applicable to improve the throughput performance and reduce interference of similar systems working in a cognitive manner.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.676-684
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• 2008

In digital video broadcasting-terrestrial (DVB-T), which is the European digital terrestrial television standard, the orthogonal frequency division multiplexing (OFDM) has been adopted for signal transmission. The main reasons using OFDM are to increase the robustness against the frequency selective fading and impulse noise, and to use available bandwidth efficiently. However, channel variation within an OFDM symbol destroys orthogonality between subcarriers, resulting in inter-carrier interference (ICI), which increases an error floor in proportional to maximum Doppler spread. This paper provides an ICI analysis in both time and frequency domains while existing literatures analyze the ICI effects mainly in frequency domain and proposes the algorithms that estimate the channel impulse response and channel variation using least square (LS) algorithm which is the most simple channel estimation technique. And we propose adaptive channel estimation algorithm that estimates the velocity of terminals. The simulation results show that proposed algorithm has similar performance with about 1.5% computational complexity of noise and ICI reduction LS algorithm in low speed environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.294-301
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• 2000

One of the most important design parameters in a microwave radio transmitting system is to reduce spurious response from the output spectrum of the transmitting system. A Local oscillator (LO) is seldom totally pure and at the least contain some LO harmonic signals. A LO or any oscillator is a transmitter if provided with a suitable radiator, conduction, or leakage path. Where mixer is employed in the output of the LO mixer generated spurs can be increased by RF amplifier. To reduce LO leakage, notch filter or band pass filter has been conventionally used. In this paper, the leakage reduction(LR) signal, which has the same magnitude and the opposite phase with respect to LO leakage signal, is added to the output of mixer of the wireless LAN system. The LO leakage is reduced by 30 dB more than the conventional methods do. The proposed method is potentially suitable for low-cost, reliable, and simple application of monolithic microwave integrated circuits (MMICs)

• KIEAE Journal
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• v.12 no.6
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• pp.77-84
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• 2012

The current architectural design of unit modular has been based on 2D of CAD program, so unit modular character which needs unit information management, as a dried-member system, has no effect on design process. The purpose of this study is We have developed a suitable BIM design process, according to various works of construction, then tried to contribute to supply and activation of the urban-life-housing based on unit modular. The BIM modeling process based on unit modular has been in order of unit combination with preparing manual classification, and, it has been constructed, at construction site, from housing foundation to roof finish by Bottom-up method. At a manufacturing factory, it has been produced in order of 1) grouping materials and parts, 2) fabricating unit boxes, and 3) interference examination of unit boxes, and each order has been classified as housing structure, architecture, plumbing process separately. At a construction site, the fabrication has been done in order of, like as a real housing construction scenario, 1) RC foundation work 2) unit module job-site-fabrication work, 3) roof truss work, 4) plumbing and HVAC work, and 5) housing interior finish work. After modeling process, the interference examination on each work of construction has finally completed modeling. The Unit modular utilizing BIM modeling can make easy housing maintenance through systematic control with preparing manual of unit module information, and securing accurate and speedy construction information. And it will promote design credibility and create maximum effect of unit modular construction method, such as construction period reduction and upgrade of construction quality, etc., through the computer simulation as real as construction environment in cyber space, and with the interfering examination.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.687-694
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• 2012

In OFDMA-based cellular system, inter-cell interference (ICI) reduces system capacity by aggravating receiving performance of the users located in edge of the cell. Therefore, to mitigate ICI is very important issue in cellular system. To deal with ICI problem, fractional frequency reuse (FFR) is introduced. FFR is an interference management technique. It separates each cell into inner cell and outer cell. Then, it allocates whole system bandwidth to inner cell and different frequency partition to each sector of outer cell. By doing this, outer cell users can ignore interferences from adjacent cells. So, the receiving performance of the cell edge users can be fairly increased. However, using FFR technique has a fatal side effect. In order to use different frequency partition among three sectors of outer cell, they can use only a third of the whole system bandwidth. Then, the reduction of available bandwidth reduces the system throughput directly. To solve this problem, we propose a new FFR method that allocates partially overlapped frequency partition to each sector of outer cell. And then, we suggest a proper overlapping ratio for practical cellular system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6A
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• pp.379-385
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• 2003

In this paper, we propose a time constant control method for sieving local minimum problem of the multiuser detector using Hopfield neural network for synchronous multi-rate code division multiple access(CDMA) system in selective fading environments and its performance is compared with that of the parallel interference cancellation(PIC). We also assume that short scrambling codes of 256 chip length are used an uplink, suggest a simple correlation estimation algorithm and circuit complexity reduction method by using cyclostationarity property of short scrambling code.It is verified that multiuser detector using Hopfield neural network more efficiently cancels multiple access interference(MAI) and obtain better bit error rate and near-far resistant than conventional detector.