• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.66-74
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• 2001

In this paper, we proposed the new structure of the Rake Finger using Walsh Switch, the shared accumulator, and the pipeline FWHT(Fast Walsh Hadamard Transform) algorithm for reducing the signal processing complexity resulting from the increase of the number of data correlators. The function simulation of the proposed architecture is performed by Synopsys tool and the timing simulation is performed by Compass tool. The number of computational operation in the proposed data correlators is 160 additions and the conventional ones is 512 additions when the number of walsh code channels is 4. As a result, it is reduced about 3.2 times other than the number of computational operation of the conventional ones. Also, the result shows that the data processing time of the proposed Rake Finger architecture is 90,496[ns] and the conventional ones is 110,696[ns]. It is 18.3% faster than the data processing time of the conventional Rake Finger architecture.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.113-120
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• 2002

This paper describes characteristics of transient voltage waveforms caused by human electrostatic discharges(ESDs). For purpose of achieving the statistics on the meaningful amplitude and initial slope for transient ESD voltage waveforms, transient voltages due to human ESDs in various conditions were observed. A voltage measuring system with a wide bandwidth from DC to 400[MHz] was employed. ESD voltage waveforms are approximately the same as ESD current waveforms. Also the simulated results, which are calculated by the reposed equivalent circuit, are closely similar to the measured voltage waveforms. ESD voltage waveforms are strongly dependent on the approach speed and material of intruder, a fast approach causes ESD voltage waveform with a steep rise time than for a slow approach. The voltage waveforms from dialect finger ESDs have a relatively long rise time of 10∼30[ns], but their peaks are low. On the other side ESD voltage waveforms causer by screwdriver with insulating handle have a steep slope with a very short, less than 1[ns] rise time, but their initial spikes are extremely high The obtained results in this work would be applied to solve ESD problems for low voltage and small current electronic devices.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.993-1000
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• 2018

This paper proposes a low-dropout voltage regulator(LDO) using self-cascode structure. The self-cascode structure was optimized by adjusting the channel length of the source-side MOSFET and applying a forward voltage to the body of the drain-side MOSFET. The self-cascode of the input differential stage of the error amplifier is optimized to give higher transconductance, but the self-cascode of the output stage is optimized to give higher output resistance, The proposed LDO using self-cascode structure was designed by a $0.18{\mu}m$ CMOS technology and simulated using SPECTRE. The load regulation of the proposed LDO regulator was 0.03V/A, whereas that of the conventional LDO was 0.29V/A. The line regulation of the proposed LDO regulator was 2.23mV/V, which is approximately three times improvement compared to that of the conventional LDO. The transient response of the proposed LDO regulator was 625ns, which is 346ns faster than that of the conventional LDO.

• Journal of the Korean Magnetics Society
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• v.17 no.5
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• pp.188-193
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• 2007

We simulated the magnetization reversal behavior of submicron-thickness magnetic films by applying pulses of sub-ns-long durations and amplitudes along the easy axis. The films were rectangular and elliptical $Ni_{80}Fe_{20}$, and their thickness was 2 nm and 4 nm. We observed different behaviors depending upon the shape and thickness of the films and found a normal non-switching in regions in which we expected complete switching after relaxation. In the elliptical film, the non-switching regions were found to be random and to be widely distributed throughout the switching map. The strong demagnetization field along the z-axis, the film thickness direction, is likely responsible for this abnormal behavior. In the rectangular film, the abnormal non-switching regions were less distributed than they were in the elliptical film due to edge domains resulting from the small $M_z$ or demagnetization field during the switching. Our simulation confirms that large demagnetization is detrimental to the ultra-fast magnetization reversal of magnetic ultra-thin films.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.63-70
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• 2005

Various schemes for mobility are currently studied in ITU-T, 3GPP, IETF, and so on. Mobility support in NGN for seamless service is necessarily required. Currently proposed mechanisms are MIPv6, $IP^2$, and Q.MMF. However the performance comparison of all existing schemes is not examined as yet. That is, the existing methods need to be compared according to each performance parameter. So, in this paper, we investigate and compare the performances of MIPv6, $IP^2$, Q.MMF to location registration. In addition, this paper presents the performance comparison of handover latency times. For this, we use NS-2 simulator. As a result of analysis, $IP^2$ shown the best performance as it is measured the minimum time and cost. And it has low handover latency time in comparison with other mechanisms.

• Journal of the Korea Society for Simulation
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• v.14 no.4
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• pp.77-86
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• 2005

[ $IP^2$ ] (IP-based IMT Network Platform) is a ubiquitous platform supporting mobility using two step If address IPha (IP host address) and IPra (IP routing address) - in a backbone network. MN (Mobile Node) in $IP^2$ maintains either Active or Dormant state, which is transferred to Active state through Paging process when communication is required. In this paper, we proposed a Paging method using proxy to resolve the problem of the conventional Paging method which transmits the Paging messages to all cells in LA (Location Area) resulting in the excessive use of network resources. Performanceevaluation of the proposed method using NS-2 showed that the usage of network resources becomes more efficient by reducing paging loads, especially under the condition of increased nodes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.78-81
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• 1999

The position and time errors of a conventional L1-band GPS receiver (1575.42MHz) are known to be about 100 m and 70 ns, respectively. These errors are mainly due to the propagation delay of GPS satellite signals through ionosphere. Various L1/L2 dual-band GPS receivers are normally used to compensate for those position and time errors by detecting an accurate propagation delay. These receivers detect the propagation delay difference between the L1 and L2 signals based on the fact that the propagation delay through ionosphere is dependent on frequency and, from which, calculate an accurate propagation delay of the GPS signals through ionosphere. In this paper, we analyzed the architecture of a L1/L2 dual-band CPS receiver by high-level simulations with Synopsys's COSSAP Tool.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.798-805
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• 2017

This paper presents a low profile multi circular ring with different radius, patch antenna with modified feed line and slotted ground. The size of the antenna is $15{\times}12mm^2$, having electrical dimensions of $0.14{\lambda}{\times}0.12{\lambda}$ (at lower initial frequency) and footprints of $180mm^2$. The proposed antenna covers 3.1 to 12.3 GHz, reflection coefficient up to -38 dB with Bandwidth ratio of 4.13:1 and fractional Bandwidth of 122%. Bandwidth dimension ratio has been calculated (which is 6246) as a proof for compact size. Thin slots introduced on the feed line provide good impedance matching for whole frequency band. Numerical simulations of the proposed antenna are reported in terms of reflection coefficient ${\leq}-10dB$, vswr 2:1, radiation pattern and group delay (ns). The proposed antenna has advantage of very small size along with better impedance match that provides a practical approach to realize it for BW enhancement and UWB applications.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.7
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• pp.743-747
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• 2008

Hierarchical overlay of heterogeneous wireless cells is considered as a promising architecture for next-generation wireless networks. This paper considers a special form of such architecture, WWAN/WLAN two-hop wireless relay networks. We first describe an undesirable scheduling phenomenon that the conventional proportional fair algorithm can cause in such networks. We, then, propose an enhanced proportional fair scheduling to remedy this problem. We demonstrate the performance of the proposed scheme via a simulation of UMTS/WLAN networks using NS-2.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1406-1415
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• 2012

Though WiMedia supports the higher data rates than other WPAN technologies, a WiMedia device cannot reach other devices which are apart from it more than 10 meter; the limited transmission range of the WiMedia protocol. In this paper, we propose a multi-hop QoS routing protocol to enable WiMedia devices to transmit real-time data to devices that is located out of transmission range. The proposed routing protocol is a hybrid routing protocol, which is the mixed protocol of table-driven and on-demand routing algorithm. In the proposed protocol, a route for a device within 2-hop is established by using the table-driven routing algorithm and a route for the device beyond 2-hop is established by using the on-demand routing algorithm. We perform ns-2 simulation to investigate the performance of the proposed routing protocol with AODV and DSDV. The simulation results show that the proposed protocol's performance is better than AODV and DSDV in terms of the throughput and delay.