• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2638-2647
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• 2010

X-MAC reduces transmission delay and energy consumption by using a short preamble instead of the existing long preamble. To solve the problem of X-MAC, this paper proposes a new MAC protocol called Express-MAC. The wireless sensor network is mainly used for the purpose of gathering event data or situation information. Especially, the transmission pattern of the sensor network with the purpose of event detection such as intrusion detection is very intermittent as well as successively occurring when a single event takes place in most cases. By reflecting sensor network's key transmission patterns as above, EX-MAC has used multi-hub path's path reservation system and awake section's transmission time reservation method in data transmission when the first event takes place. The awake time reservation in transmission path has improved successive data transmission's end-to-end delay, and it has also increased efficiency in terms of energy consumption by reducing the preamble length of data transmission and reception node.

• ETRI Journal
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• v.25 no.1
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• pp.1-8
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• 2003

This paper introduces an efficient iterative decoding method for high-dimensional block turbo codes. To improve the decoding performance, we modified the soft decision Viterbi decoding algorithm, which is a trellis-based method. The iteration number can be significantly reduced in the soft output decoding process by applying multiple usage of extrinsic reliability information from all available axes and appropriately normalizing them. Our simulation results reveal that the proposed decoding process needs only about 30% of the iterations required to obtain the same performance with the conventional method at a bit error rate range of $10^{-5}\;to\;10^{-6}$.

• Journal of IKEEE
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• v.12 no.2
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• pp.81-86
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• 2008

In wireless communication system using 2.4GHz radio link, data rate varies with time due to interferences, which causes the performance degradation. Therefore, effective transmission methods are required to obtain better performance according to varying data rate. This paper proposes a novel method that increases the data rate, as well as the influence of different loop-filter bandwidths on the performance of the PLL. Experimental results show that the proposed method is effective because it can achieve higher throughput in various data rate.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1259-1261
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• 1999

The paper proposes a simple method to calculate the portion of real power losses allocated to individual loads. The method is implemented by loss distribution factors, and analyses the share of loads in transmission line losses. Effectiveness of the algorithm is verified by a computer simulation. The results can be used to compute the cost of ancillary services under deregulated environment in electric power industries.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.207-215
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• 1993

With the aid of finite element method, this paper deals with the problem of structural response variability of transmission tower subjected to the spatial variability of material properties, Young's modulus herein. The spatial variability of material property are modeled as two-dimensional stochastic field which has an isotropic auto-correlation function. Response variability has been computed based on two numerical techniques, such as the Neumann expansion method in conjunction with the Monte Carlo simulation method. The results by these numerical methods are compared with those by the deterministic approach.

• Journal of the Optical Society of Korea
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• v.11 no.1
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• pp.6-9
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• 2007

We propose a wavelength allocation method for bidirectional transmission in a coarse wavelength division multiplexing channel. The method can be accommodated by assigning a different upstream wavelength from the downstream wavelength at room temperature to eliminate penalties induced by backscattering, including Rayleigh backscattering. We suggest a procedure to obtain the minimum wavelength difference.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1997.06a
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• pp.49-54
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• 1997

For the purpose of a flexible coded video transmission over a heterogeneous network, we propose a new packetization method for coded video data. The proposed method achieves small degradation of coded picture quality in case of packet discard at the network node and does not require heavy processing load for bitrate control operation. Computer simulation results show that the bitrate reduction from 384 kb/s to 192 kb/s does not cause severe degradation in picture quality.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.5
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• pp.355-360
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• 1991

A transmission-line discontinuities are analyzed by Finite Element Method. We use quasi-static approxmation to determine the circuit parameters of discontinuities. Delta formulation is introduced so that the cancellation error of potential calculation is reduced. To verify this method, capacitance of coaxial cable with discontinuous and coupling capacitances are calculated by modal expansion. This approach can be used for arbitrary discontinuous conducting patterns of microwave devices.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.12
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• pp.1918-1925
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• 1989

A method for computing the capacitance and inductance matrix for 2-D multiconductor transmission lines with arbitrary cross section in dielectric medium is presented. The integral equation is obtained by using a free space Green function in conjunction with free and bound charges existing on boundary surfaces. The numerical analysis is based on the moment method using point matching and Galerkin method. And kthe scheme to reduce memory and computation time is presented for symmetric structure.

• Proceedings of the KIEE Conference
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• summer
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• pp.70-72
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• 2004

The paper proposes a new method to process transmission losses in power market operation using loss distribution factors and then compares the proposed method with the one using marginal loss factors. Effectiveness of the algorism is verified by a computer simulation.