• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.191-198
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• 2003

In this paper, we analyze the performance of transmit diversity techniques which are the key technologies of the third generation mobile communication systems. Transmit diversity techniques adopted on the specification of 3GPP are classified into open-loop and closed-loop methods depending on the existence of feedback data. In WCDMA systems, the DPCH signal is space-time coded to provide a mobile station with diversity. Computer simulations shall be performed to analyze and compare their performance considering the effect of mobile speed, number of path, power control, and delay of feedback with the WCDMA slot format #13 for application to WCDMA systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1324-1329
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• 2013

The WiMedia Alliance has specified a Distributed Medium Access Control (D-MAC) protocol based on UWB for high speed wireless home networks and WPANs. In this paper, firstly, the fair SoQ-based Distributed Reservation Protocol (DRP) for D-MAC is analyzed. And a novel SoQ-based relay transmission protocol is proposed to overcome DRP conflicts fast. In the proposed protocol, each device executes the Satisfaction of QoS (SoQ) time slot allocation algorithm independently. And, in order to give the loser device due to DRP conflicts another chance to maintain QoS resources, the proposed relay transmission protocol helps the device reserve another indirect link maintaining the required QoS resources via a relay node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.467-476
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• 2003

In this paper, we propose an efficient MAC scheduling algorithm for supporting Bluetooth scatternet operations. Our proposed algorithm improves overall performances of scatter mode［2, 3] and considers QoS requirements of each link of the bridge node of a scatternet. Scatter mode is based on time division scheduling and provides every links of a scatternet with fair service opportunities. However, since each Bluetooth devices has various traffic characteristics. fair allocation of service opportunities is not efficient and may cause extravagance of wireless resources. Therefore, we propose a new efficient inter-piconet scheduling algorithm compliant with the current Bluetooth specification［1］, and demonstrate its improved performances via computer simulations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.870-877
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• 2014

Geostationary satellites undergo various orbital perturbations and this results in location change. Therefore, all the geostationary satellites use the thruster in order to control the location change. For this purpose, the suitable amount of liquid propellant is mounted and the amount of propellant is reduced as time goes by. This means that the lifetime of the satellite depends on the residual propellant amount. Therefore precise residual propellant gauging is very important for the mitigation of economic losses arised from premature removal of satellite from its orbit, satellites replacement planning, slot management and so on. In this paper, we introduce the propellant gauging methods used in the geostationary satellites and the propellant gauging method studied in the laboratory level.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.899-906
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• 2003

In this paper, a channel access control algorithm and a slot allocation algorithm are proposed as MAC protocol for multimedia services in TDMA/TDD-based wireless ATM networks. In the proposed protocol, VBR terminals that require real-time services transmit a reservation request through a random access minislot. VBR terminals, which are successfully transmitted the reservation request, transmits the dynamic parameters through a dynamic parameter minislot without contention. On the other hand, ABR terminals transmit a reservation request with contention basis whenever a non-real-time traffic burst is generated. Based on the received dynamic parameters and the number of requested slots, the base station scheduler allocates a dynamic parameter minislot as well as uplink data slots into VBR terminals. Also the scheduler allocates uplink data slots into ABR terminals in proportion to the number of requested slots.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.194-196
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• 2001

Light dimming is based on adjusting the voltage which gets to the lamp. Light dimming has been possible for many decades by using adjustable power resistors and adjustable transformers. The power electronics have proceeded quietly since 1960. Between 1960-1970 thyristors and triacs came to market. Using those components it was quite easy to make small and inexpensive light dimmers which have goof efficiency. This type of electronic light dimmers became available after 1970 and are nowadays used in very many locations like homes, restaurants, conference rooms and in stage lighting. But the problem of thyristor dimmer have been that it has poor efficiency and voltage drop. Recently IGBT(Insulated Gate Bipolar Transistor) control is a new way to do light dimming for improving this problems. IGBT dimmer has many other advantages over traditional thyristor dimmer there are no huge current spikes and EMI caused by turn on Using IGBT it is possible to make the turn-off rate relatively slot to achieve quite operations in terms of EMI and acoustical or incandescent lamp filament noise. For the development of IGBT dimmer. This paper shows the effects of IGBT dimmer compared with thyristor dimmer through a simulation using EMTDC.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1245-1250
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• 2015

In this paper, a compact CPW-fed antenna for 2.45 GHz band WLAN applications is presented. The proposed antenna which has a geometry of folded stub and slot is fabricated into an inexpensive FR-4 substrate that has a dielectric constant of 4.2 and a thickness of 1.0 mm with optimized parameters obtained by simulation, and then measured. From measured result, we confirmed available operation as antenna for WLAN applications by obtaining the return loss level of < -10 dB in the frequency band of 2.4-2.484 GHz.

• KIISE Transactions on Computing Practices
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• v.22 no.12
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• pp.654-662
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• 2016

With the advent of autonomous cars, we explored the problems which will soon arise while parking in car parks. These include structure of parking lot suitable for autonomous cars, finding the closest parking slot available, and navigation to the location. We provide an initial solution, wherein we use a central server and the graph of the parking lot to guide cars to the closest parking slots available. Our experiments have shown that the proposed method is effective for the controlled parking for self-driving cars.

• Journal of Korea Multimedia Society
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• v.18 no.12
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• pp.1547-1554
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• 2015

Because there are numerous near field communication (NFC) technical standards and each standard has an independent communication protocol, an NFC software for controlling the protocols are significantly complicated. Especially, the anticollision algorithm for establishing the initial communication connection is classified into bit-oriented or time slot method according to the technical standards. Moreover, the anticollision algorithm is generally manipulated in software because of its complexity. In addition, since one host processor is shared by multiple modems in a connectivity SoC, embedding several communication modems with an NFC modem, the spare computing resources can be utilized for other modems by reducing the software cost to control the NFC modem. In this paper, we propose new design methods of the NFC modem for supporting anticollision, framing and bit rate detection in the hardware to reduce the software overhead. Therefore, the utilization of the NFC technology is enhanced in the connectivity SoC by minimizing the cost of software.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1104-1111
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• 2012

Airborne tactical networks is used to air-to-air or air-to-ground operation and have a large propagation delay. All nodes share the data by using TDMA-based broadcasting. In airborne tactical networks, each time slot needs the guard time to ensure the broadcasting because the collisions occur due to the large propagation delay. However, the channel utilization of the networks can be greatly degraded due to the waste of guard time. In this paper, we propose Inter-Transmitter Distance-Based TDMA (ID-TDMA) scheme which ensures the broadcasting while improving the channel utilization by reducing the guard time with the inter-transmitter distance information. The proposed scheme shows the effectiveness through the performance evaluation.