• ETRI Journal
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• v.37 no.3
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• pp.439-449
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• 2015

Human body communication (HBC) is being recognized as a new communication technology for mobile and wearable devices in a body area network (BAN). This paper presents co-channel interference experienced by HBC supporting the physical layer in the IEEE 802.15.6 BAN standard. To analyze the co-channel interference, a co-channel interference model is introduced, and space-domain and time-domain parameters representing an interference environment are generated using the co-channel interference model. A new signal-to-interference ratio (SIR) parameter depending on the peak amplitudes of the data signals causing co-channel interference is defined; co-channel interference can be easily analyzed and modelled using the newly defined SIR. The BER degradation model derived using the co-channel interference model and SIR in this paper can be effectively used to estimate the performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.110-118
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• 2007

In multi-hop wireless network, multi-channel makes it possible to enhance network performance because it reduces channel interferences md contentions. Recently several schemes have been proposed in the literatures to use multi-channel. Especially, MCR(Multi channel routing protocol), which utilize hybrid interface assignment, is a prominent routing protocol. MCR uses simple way to change channel but efficiently reduce channel interferences. In this paper, we propose a load-aware channel selection algorithm called LCS that enhances the channel switching algerian used in MCR protocol. In LCS, channel of a node is assigned based on collected information about queue length of neighbors. Moreover this paper evaluates the performance of in by using simulation test and testbed demonstration. Test results show that the MCR with LCS outperforms the naive MCR.

• Biomolecules & Therapeutics
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• v.9 no.4
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• pp.237-243
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• 2001

This study was attempted to investigate the effects of cromakalim (CRK), $K^{+}$ channel opener, and glibenclamide (GLY), $K^{+}$ channel blocker, on intestinal function of rabbit. CRK supressed the tension and spontaneous movement of intestinal strips. CRK enhanced the tension and spontaneous movement of strips induced by acetylcholine. Also the inhibiting effect of dopamine was potentiated by CRK. GLY augmented the tension, but did not affect the spontaneous movement of strips. GLY inhibited tension and spontaneous movements in intestinal strips induced by acetylcholine, GLY blocked the dopamine-induced attenuation of tension, but not the decrease of spontaneous movements in intestinal strips. The present studies suggest that $K^{+}$ channel opening suppresses intestinal movements, whereas it's blockade enhances intestinal movements in rabbit.abbit.

• ETRI Journal
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• v.34 no.5
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• pp.771-774
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• 2012

Typical channel allocation algorithms for secondary users do not include processes to reduce the frequency of switching from one channel to another caused by random interruptions by primary users, which results in high packet drops and delays. In this letter, with the purpose of decreasing the number of switches made between channels, we propose a nonparametric channel allocation algorithm that uses robust kernel density estimation to effectively schedule idle channel resources. Experiment and simulation results demonstrate that the proposed algorithm outperforms both random and parametric channel allocation algorithms in terms of throughput and packet drops.

• Journal of Information Processing Systems
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• v.11 no.3
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• pp.342-353
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• 2015

It is widely accepted that single carrier frequency division multiple access (SC-FDMA) is an excellent candidate for broadband wireless systems. Channel estimation is one of the key challenges in SC-FDMA, since accurate channel estimation can significantly improve equalization at the receiver and, consequently, enhance the communication performances. In this paper, we study the application of compressive sensing for sparse channel estimation in a SC-FDMA system. By skillfully designing pilots, their patterns, and taking advantages of the sparsity of the channel impulse response, the proposed system realizes channel estimation at a low cost. Simulation results show that it can achieve significantly improved performance in a frequency selective fading sparse channel with fewer pilots.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.431-435
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• 2010

In this paper, we investigated the dependence of device performance and hot carrier lifetime on the channel direction of PMOSFET. $I_{D.sat}$ vs. $I_{Off}$ characteristic of PMOSFET with <100> channel direction is greater than that with <110> channel direction because carrier mobility of <100> channel direction is greater than that of <110> channel direction. However, hot carrier lifetime for <110> channel direction is much lower than that with <110> channel due to the greater impact ionization rate in the <100> channel direction. Therefore, concurrent consideration of reliability characteristics and device performance is necessary for channel strain engineering of MOSFETs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.788-794
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• 2005

In this paper, we focus on the potential of dual polarized antennas in mobile system. thus, this paper designs exact dual polarized channel with Spatial Channel Model (SCM) and investigates the performance for certain environment. Using proposed the channel model; we know estimates of the channel capacity as a function of cross polarization discrimination (XPD) and spatial fading correlation. It is important that the MIMO channel matrix consists of Kronecker product dividable spatial and polarized channel. Through the channel characteristics, we propose an algorithm for the adaptation of transmit antenna configuration to time varying propagation environments. The optimal active transmit antenna subset is determined with equal power allocated to the active transmit antennas, assuming no feedback information on types of the selected antennas. We first consider a heuristic decision strategy in which the optimal active transmit antenna subset and its system capacity are determined such that the transmission data rate is maximized among all possible types. This paper then proposes singular values decision procedure consisting of Kronecker product with spatial and polarize channel. This method of singular value decision, which the first channel environments is determined using singular values of spatial channel part which is made of environment parameters and distance between antennas. level of correlation. Then we will select antenna which have various polarization type. After spatial channel structure is decided, we contact polarization types which have considerable cases It is note that the proposed algorithms and analysis of dual polarized channel using SCM (Spatial Channel Model) optimize channel capacity and reduce the number of transmit antenna selection compare to heuristic method which has considerable 100 cases.

• Journal of electromagnetic engineering and science
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• v.7 no.4
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• pp.195-200
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• 2007

Doubly-selective channel estimator for orthogonal frequency division multiplexing(OFDM) systems is proposed in this paper. Based on the generalized complex exponential basis expansion model(GCE-BEM), we describe the time-variant channel with time-invariant coefficients over multiple OFDM blocks. The time variation of the channel destroys the orthogonality between subcarriers, and the resulting channel matrix in the frequency domain is no longer diagonal, but the main interference comes from the near subcarriers. Based on this, we propose a channel estimator with low pilot ratio. We first develop a least-square(LS) estimator under the assumption that only the maximum Doppler frequency and the channel order are known at the receiver, and then verify that the correlation matrix of inter-channel interference(ICI) is a scaled identity matrix based on which we derive an optimal pilot insertion scheme for the LS estimator in the sense of minimum mean square error. The proposed estimator has the advantages of low pilot ratio and robustness against inter-carrier interference.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2218-2230
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• 2012

In this paper, we propose an efficient channel delay estimation method for orthogonal frequency-division multiplexing (OFDM) systems, especially over doubly-selective fading channels which are selective in both the symbol time domain and subcarrier frequency domain. For the doubly-selective fading channels in single frequency network (SFN), long and strong echoes exist and thus the conventional discrete Fourier Transform (DFT) based channel delay estimation system often fails to produce the exact channel delay profile. Based on the analysis of the discrete-time frequency response of the channel impulse response (CIR) coefficients in the DFT-based channel delay estimation system, we develop a method to effectively extract the true CIR from the aliased signals by employing a simple narrow-band low-pass filter (NB-LPF). The performance of the proposed system is verified using the COST207 TU6 SFN channel model.

• YAKHAK HOEJI
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• v.43 no.5
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• pp.674-681
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• 1999

This study was performed to investigate the effects of renal denervation and cromakalim, a K+ Channel opener, on central diuretic action of glibenclamide, an ATP-dependent K+ Channel blocker, in dog. Diuretic action of glibenclamide administered into the vein was weakened markedly by renal denervation and pretreatment of of cromakalim. Above results suggest that central diuretic action of glibenclamide is mediated by renal nerves and K+ Channel localized in kidney.