• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.917-922
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• 2018

In the conventional interchannel interference self-cancellation (ICI-SC) schemes, the length of sampling window is the same as the symbol length of orthogonal frequency division multiplexing (OFDM). Thus, the number of complex operations to compute the interference coefficient of each subchannel is significantly increased. To solve this problem, we present an approximated mathematical model for the coefficients of ICI-SC schemes. Based on the proposed approximation, we analyze mean squared error (MSE) and computational complexity of the ICI-SC schemes with the length of sampling window. As a result, the presented approximation has an error of less than 0.01% on the MSE compared to the original equation. When the number of subchannels is 1024, the number of complex computations for the interference coefficients is reduced by 98% or more. Since the computational complexity can be remarkably reduced without sacrificing the self-cancellation capability, it is considered that the proposed approximation is very useful to develop an algorithm for the ICI-SC scheme.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.729-736
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• 2018

Due to the frequency offset, interchannel interference (ICI) is occurred in the received symbols of the orthogonal frequency division multiplexing (OFDM) systems. The ICI self-cancellation (ICI-SC) technique appropriately adjusts the subchannel signal assignment of the OFDM symbols, thereby canceling the interference caused by other subchannels. The conventional adjacent symbol repetition (ASR) method can reduce the interference caused by remote subchannels. However, it may not mitigate or even increases the ICI produced by some nearest subchannels. To solve the problem, a new ASR based ICI-SC technique is proposed and its performance is analyzed in this paper. Here, a t-parameter obtained by the interference coefficients of 3 successive subchannels is applied. As a result, the proposed method has the same capability to reduce the influence of remote subchannels. However, it can reduce the ICI caused by the nearest subchannels significantly.

• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.199-203
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• 1996

To study the magnetization reversal behavior of Co/Pd multilayers, we first demagnetized the samples by the field-demagnetized method and then measured initial curves and minor loops. The coercivity and the perpendicular magnetic anisotropy were obtained from the perpendicular and parallel magnetization curves measured at different temperatures. We interpret our experimental results by applying several qualitative and semiquantative approaches. From these study, we found that the magnetization reversal behavior is dominated by the domain wall pinning for all samples and the coercivity incremental tendency can be explained by Kronmuller's formula $H_c(T)\;{\propto}\;r_0.K_u$.

• Journal of the Korean Magnetics Society
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• v.7 no.2
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• pp.97-102
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• 1997

Off-track capability is used to determine the track pitch of hard disk drive system, and the off-track capability as a function of track pitch is called 747 curve. In this paper, 747 curves were simulated with computer. Side reading and recording parameters were obtained by magnetic field analysis using 3-D finite element method. Head read signal and noise voltages for calculation of signal to noise ratio (SNR) were obtained using reciprocity theorem. According to the 747 curves thus obtained, the off-track capability was increased as erase band width increased and as effective signal to noise ration $(SNR_{eff}}$ decreased. A simulated 747 curve and a measured 747 curve (using spin stand) of a planar silicon head with track width of 4.1 um were very similar, which indicated that the simulation was carried out properly.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.1-8
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• 2005

In this paper, peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) with respect to the subchannel coding schemes for interchannel interference (ICI) self-cancellation is analyzed. It is shown theoretically and experimentally that a shaping component is generated in the transmitted sequence in the conventional correlative coding where a pair of antipodal signals is assigned in adjacent subchannels. Due to the shaping component, the signal powers in the mid and edges of a symbol are scaled by different weighting coefficients, resulting in increased PAPR. To overcome this problem a simple adjacent subchannel coding scheme is presented in this paper. In the new scheme, the shaping component caused by partial repetition of signals is eliminated by assigning a pair of signals in which phase difference varies signal-to-signal. As results, the new scheme has 2-3 dB smaller PAPR than the conventional ICI self-cancellation OFDM while maintaining much higher carrier-to-interference ratio than a normal OFDM system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.513-519
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• 2021

Metallic suture anchors are very useful and common fixation devices that are inserted into the target bone to sustain the tendon of a patient with musculus supraspinatus tendon ruptures. On the other hand, the presence of a metallic material prosthesis, such as a metal suture anchor, causes severe MR imaging artifacts, including field distortion, signal loss, and failure of fat suppression. The difference in magnetic susceptibility between metal and other organic materials causes magnetic field distortion surrounding the prosthesis. The resulting magnetic field inhomogeneity makes the images with a lower signal-to-noise ratio and distortion. For a patient with a suture anchor implanted, MR imaging is the golden standard for determining the postoperative prognosis, and a fat-saturation sequence is one of the imaging methods most affected by metal-induced artifacts. In this study, three fat-saturation sequences were compared. Artifact quantification and contrast comparison between the supraspinatus tendon and the surrounding muscle were presented. The images obtained using the STIR pulse sequence showed fewer susceptibility artifacts and better visibility in the supraspinatus tendon and the tissue area. Therefore, the STIR sequence is the most appropriate fat-saturation imaging method for patients with a metallic prosthesis.