• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.3 s.345
• /
• pp.59-67
• /
• 2006

OFDM (Orthogonal frequency Division Multiplexing) systems convert serial data stream to N parallel data streams and modulate them to N orthogonal subcarriers. Thus spectrum utilization efficiency of the OFDM systems are high and high-speed data transmission is possible. However, with the OFDM systems using the same modulation method at all subcarriers, the error probability is dominated by the subcarriers which experience deep fades. Therefore, in order to enhance the performance of the system adaptive modulation is required, with which the modulation methods of the subcarriers are determined according to the estimated SNRs. The IEEE 802.11a system selects various transmission speed between 6 and 54 Mbps according to the modulation mode. There are three typical methods for SNR estimation: Direct estimation method uses the frequency domain symbols to estimate SNR directly by minimizing MSE (Mean Square Error), EVM method utilizes the distance between the demodulated constellation points and received complex values, and the method utilizing the Viterbi algorithm uses the cumulative minimum distance in decoding process to estimate the SNR indirectly. Through comparison analyses of three methods we propose a new SNR estimation method, which employs both the EVM method and the Viterbi algorithm. Finally, we perform extensive computer simulations to confirm the performance improvement of the proposed adaptive OFDM systems on the basis of IEEE 802.11a.

• Journal of Internet Computing and Services
• /
• v.20 no.5
• /
• pp.113-119
• /
• 2019

The key features of 5G mobile communications recently commercialized can be represented by High Data Rate, Connection Density and Low Latency, of which the features most distinct from the existing 4G will be low Latency, which will be the foundation for various new service offerings. AR and self-driving technologies are being considered as services that utilize these features, and 5G Network Latency is also being discussed in related standards. However, it is true that the discussion of E2E Latency from a service perspective is much lacking. The final goal to achieve low Latency at 5G is to achieve 1ms of air interface based on RTD, which can be done through Ultra-reliable Low Latency Communications (URLLC) through Rel-16 in early 20 years, and further network parity through Mobile Edge Computing (MEC) is also being studied. In addition to 5G network-related factors, the overall 5G E2E Latency also includes link/equipment Latency on the path between the 5G network and the IDC server for service delivery, and the Processing Latency for service processing within the mobile app and server. Meanwhile, it is also necessary to study detailed service requirements by separating Latency for initial setup of service and Latency for continuous service. In this paper, the following three factors were reviewed for initial setup of service. First, the experiment and analysis presented the impact on Latency on the Latency in the case of 1 Data Lake Setup, 2 CRDX On/Off for efficient power, and finally 3H/O on Latency. Through this, we expect Low Latency to contribute to the service requirements and planning associated with Latency in the initial setup of the required services.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.48 no.5
• /
• pp.25-33
• /
• 2011

This work proposes a skinny-type 10b 50MS/s 0.13um CMOS three-step pipeline ADC for CIS applications. Analog circuits for CIS applications commonly employ a high supply voltage to acquire a sufficiently acceptable dynamic range, while digital circuits use a low supply voltage to minimize power consumption. The proposed ADC converts analog signals in a wide-swing range to low voltage-based digital data using both of the two supply voltages. An op-amp sharing technique employed in residue amplifiers properly controls currents depending on the amplification mode of each pipeline stage, optimizes the performance of op-amps, and improves the power efficiency. In three FLASH ADCs, the number of input stages are reduced in half by the interpolation technique while each comparator consists of only a latch with low kick-back noise based on pull-down switches to separate the input nodes and output nodes. Reference circuits achieve a required settling time only with on-chip low-power drivers and digital correction logic has two kinds of level shifter depending on signal-voltage levels to be processed. The prototype ADC in a 0.13um CMOS to support 0.35um thick-gate-oxide transistors demonstrates the measured DNL and INL within 0.42LSB and 1.19LSB, respectively. The ADC shows a maximum SNDR of 55.4dB and a maximum SFDR of 68.7dB at 50MS/s, respectively. The ADC with an active die area of 0.53$mm^2$ consumes 15.6mW at 50MS/s with an analog voltage of 2.0V and two digital voltages of 2.8V ($=D_H$) and 1.2V ($=D_L$).

• Journal of Arbitration Studies
• /
• v.13 no.2
• /
• pp.459-488
• /
• 2004

General interest in the out-of-court dispute resolution system are mounting in Korea, and the spread of ADR(alternative dispute resolution) is the worldwide trend. In addition, it was confirmed that the resolution of disputes by ADR such as the decision based on arbitration made by the Prime Ministerial Administrative Decision Committee is no longer in exclusive possession of the civil case. The activation of ADR could lead to the smooth agreement between parties by getting away from the once-for-all mode of decision such as the dismissal of the application or the cancellation of disposal and the like in relation to administrative cases for the years. In consequence, it is anticipated that the administrative litigation that applicants have filed by not responding to the administrative decision would greatly reduce in the future. But, it would be urgent to provide for the legal ground of the ADR system through the revision of related laws to take root in our society because ADR has no legal binding power relating to the administrative case due to the absence of its legal grounds. The fundamental reason for having hesitated to introduce ADR in relation to the administrative case for the years is the protective interest of the third party as well as the public interest that would follow in case the agreement on the dispute resolution between parties brings the dispute to a termination in the domain of the public law. The disputes related to the contract based on the public law and the like that take on a judicial character as the administrative act have been settled within the province of ADR by applying the current laws such as the Civil Arbitration Law, Mediation Law, but their application to the administrative act of the administrative agency that takes on a character of the public law has been hesitated. But as discussed earlier, there are laws and regulations that has the obscure distinction between public and private laws. But there is no significant advantage in relation to the distinction between public and private laws. To supplement and cure these defects it is necessary to include the institutional arrangement for protection of the rights and benefits of the third party, for example the provision of the imposition of the binding power on the result of ADR between parties, in enacting its related law. It can be said that the right reorganization of the out-of-court dispute resolution system in relation to the administrative case corresponds with the ideology of public administration for cooperaton in the Administrative Law. It is high time to discuss within what realm the out-of-court dispute resolution system, alternative dispute resolution system, can be accepted and what binding power is imposed on its result, not whether it is entirely introduced into the administrative case. It is thought that the current Civil Mediation Law or Arbitration Law provides the possibility of applying arbitration or mediation only to the civil case, thereby opening the possibility of arbitration in the field of the intellectual property right law. For instance, the act of the state is not required in establishing the rights related to the secret of business or copyrights. Nevertheless, the disputes arising from or in connection with the intellectual property rights law is seen as the administrative case, and they are excluded from the object of arbitration or mediation, which is thought to be improper. This is not an argument for unconditionally importing ADR into the resolution of administrative cases. Most of the Korean people are aware that the administrative litigation system is of paramount importance as the legal relief for administrative cases. Seeing that there is an independent administrative decision system based on the Administrative Decision Law other than administrative litigation in relation to administrative cases, the first and foremost task is the necessity for the shift in thinking of people, followed by consideration of the plan for relief of the rights through the improvement of the administrative decision system. Then, it is necessary to formulate the plan for the formal introduction and activation of ADR. In this process, energetic efforts should be devoted to introducing diverse forms of ADR procedures such as settlement conference, case evaluation, mini-trial, summary jury trial, early neutral evaluation adopted in the US as the method of dispute resolution other than compromise, conciliation, arbitration and mediation

• Journal of KIISE:Computing Practices and Letters
• /
• v.13 no.7
• /
• pp.520-533
• /
• 2007

The CRM(Customer Relationship Management) is the business strategy model for higher profits and competitive power of the enterprise in a new business environment. The large-scale customer response service technique uses internet, e-mail, SMS (Short Message Service), Telephony service, DM(Direct Mail) by customer channel point. Recently, business model diversify for new contract and retaining existing customer to the effort for a profitable model of business. This paper is based on Avaya PDS(Predictive Dialing System) model for CRM bond center. If the number of "available" agents are less than the number of inbound channels, then there may be real-time response problems in PDS system implemented. The Organization cannot afford to have many agents in available mode because of the high cost of manpower. This paper provides two contributions to the study. First, we present Call Object Management Mechanism of Customer Channel integration for reduce outbound consulting and reduce CallBack data in the PDS. Second, we design and implement the proposed system. Our simulation results show analysis of old model and proposed model. The proposed model can be efficiently used in Large-scale CRM.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.39 no.3
• /
• pp.59-64
• /
• 2002

In the RFID system using ISM-band, The tag mounted at the object has used the DC power by rectifying the RF signals of the small antenna for operating the micro-controller and memory. The performance of the tag would be reduced because of the second harmonics generated by the nonlinearity of the semiconductor and the spurious signal excited the high order mode of the antenna. This paper has realized the novel type low-pass filter with "the Stub-I type DGS slot structure" to improve the efficiency of the tag by suppressing the harmonics. The optimized frequency character at the pass-band/stop-band has obtained by tuning the stub width and slit width of I type slot. The measured result of the LPF has the cutoff frequency 3.25 GHz, the insertion loss about -0.29~-0.3 dB at pass-band 2.4 GHz~2.5 GHz, the return loss about -27.688~-33.665 dB at pass-band with a good performance, and the suppression character is about -19.367 dB at second harmonics frequency 4.9 GHz. This DGS LPF may be applied the various application as the RFID, WLAN to improve the efficiency of the system by suppressing the harmonics and spurious signals. 

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.135-135
• /
• 2015

Tubes are of extreme importance in industries as for fluid channels or wave guides. Furthermore, some weapon systems such as cannons use the tubes as gun barrels. To increase the service life of such tubes, a protective coating must be applied to the tubes' inner surface. However, the coating methods applicable to the inner surface of the tubes are very limited due to the geometrical restriction. A small-diameter cylindrical magnetron sputtering gun can be used to deposit coating layers on the inner surface of the large-bore tubes. However, for small-bore tubes with the inner diameter of one inch (~25 mm), the magnetron sputtering method can hardly be accommodated due to the space limitation for permanent magnet assembly. In this study, a new approach to coat the inner surface of small-bore tubes with the inside diameter of one inch was developed. Instead of using permanent magnets for magnetron operation, an external electro-magnet assembly was adopted around the tube to confine the plasma and to sustain the discharge. The electro-magnet was operated in pulse mode to provide the strong axial magnetic field for the magnetron operation, which was synchronized with the negative high-voltage pulse applied to the water-cooled coaxial sputtering target installed inside the tube. By moving the electro-magnet assembly along the tube's axial direction, the inner surface of the tube could be uniformly coated. The inner-surface coating system in this study used the tube itself as the vacuum chamber. The SS-304 tube's inner diameter was 22 mm and the length was ~1 m. A water-cooled Cu tube (sputtering target) of the outer diameter of 12 mm was installed inside of the SS tube (substrate) at the axial position. The 50 mm-long electro-magnet assembly was fed by a current pulse of 250 A at the frequency and pulse width of 100 Hz and 100 usec, respectively. The calculated axial magnetic field strength at the center was ~0.6 Tesla. The central Cu tube was synchronously driven by a HiPIMS power supply at the same frequency of 100 Hz as the electro-magnet and the applied pulse voltage was -1200 V with a pulse width of 500 usec. At 150 mTorr of Ar pressure, the Cu deposition rate of ~10 nm/min could be obtained. In this talk, a new method to sputter coat the inner surface of small-bore tubes would be presented and discussed, which might have broad industrial and military application areas.

• Journal of Energy Engineering
• /
• v.7 no.2
• /
• pp.194-201
• /
• 1998

In electric commuter trains using AC motors, lots of GTO thyristors and diodes are needed for power controls. These semiconductors generate heat about 1~2 kW, and for cooling which perfluorocarbon(PFC) heat pipes have been in use for the last two decades. The present study was investigated on the effects of such important design parameters as structure of internal surface (grooved or smooth), fill charge ratio, and inclinating angle from a vertical on heat transfer coefficients at both evaporators and condensers. To obtain experimental data, several heat pipes of the same geometry of 520 mm long and diameter of 15.88 mm but different in fill charge ratio and internal surface structure were designed and fabricated. For prediction of the heat transfer coefficients, related expressions were examined and the results of calculations were compared with experimental data. Performance tests were conducted while heat pipes operated at mode of thermosyphons. High enhancements of heat transfer coefficient were obtained internal grooves. In these cases, the evaporating heat transfer coefficients distributed in the range of 2~5.5 kW/$m^2$K, with an increase of heat flux from 15~45 kW/$m^2$. These experimental data were in good agreement with Rohsenow's expression based on nucleate boiling when correction factor $C_R$=1.3 was encountered. In addition, the condensation heat transfer coefficients were distributed from 1.5 to 3.5 kW/$m^2$K, and the data were in good agreements with Nusselt's correlation, based on filmwise condensation on vertical plate, when choosing a correction factor $C_N=4$. A fill charge ratio of 40~100% were recommended, and the in clination angle effects were negligible when the angle was higher then 30$^{\circ}$.

• Journal of Energy Engineering
• /
• v.20 no.3
• /
• pp.185-190
• /
• 2011

This paper describes design, fabrication, and evaluation of the conduction cooled high temperature superconducting (HTS) magnet for superconducting magnetic energy storage (SMES). The HTS magnet is composed of twenty-two of double pancake coils made of 4-ply conductors that stacked two Bi-2223 multi-filamentary tapes with the reinforced brass tape. Each double pancake coil consists of two solenoid coils with an inner diameter of 500 mm, an outer diameter of 691 mm, and a height of 10 mm. The aluminum plates of 3 mm thickness were arranged between double pancake coils for the cooling of the heat due to the power dissipation in the coil. The magnet was cooled down to 5.6 K with two stage Gifford McMahon (GM) cryocoolers. The maximum temperature at the HTS magnet in discharging mode rose as the charging current increased. 1 MJ of magnetic energy was successfully stored in the HTS magnet when the charging current reached 360A without quench. In this paper, thermal and electromagnetic behaviors on the conduction cooled HTS magnet for SMES are presented and these results will be utilized in the optimal design and the stability evaluation for conduction cooled HTS magnets.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.12
• /
• pp.105-112
• /
• 2009

In this paper, we investigated abnormal ESD failure on guard-rings in the smart power IC fabricated with $0.35{\mu}m$ Bipolar-CMOS-DMOS (BCD) technology. Initially, ESD failure occurred below 200 V in the Machine Model (MM) test due to current crowding in the parasitic diode associated with the guard-rings which are generally adopted to prevent latch-up in high voltage devices. Optical Beam Induced Resistance Charge (OBIRCH) and Scanning Electronic Microscope (SEM) were used to find the failure spot and 3-D TCAD was used to verify cause of failure. According to the simulation results, excessive current flows at the comer of the guard-ring isolated by Local Oxidation of Silicon (LOCOS) in the ESD event. Eventually, the ESD failure occurs at that comer of the guard-ring. The modified comer design of the guard-ring is proposed to resolve such ESD failure. The test chips designed by the proposed modification passed MM test over 200 V. Analyzing the test chips statistically, ESD immunity was increased over 20 % in MM mode test. In order to avoid such ESD failure, the automatic method to check the weak point in the guard-ring is also proposed by modifying the Design Rule Check (DRC) used in BCD technology. This DRC was used to check other similar products and 24 errors were found. After correcting the errors, the measured ESD level fulfilled the general industry specification such as HBM 2000 V and MM 200V.