• Journal of KIISE:Databases
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• v.37 no.2
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• pp.121-126
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• 2010

This paper proposes an efficient index scheduling technique for kNN query processing in multiple wireless broadcast channel environment. Previous works have to wait for the next cycle if the required child nodes of the same parent node are allocated in the same time slot on multiple channel. Our proposed method computes the access frequencies of each node of R tree at the server before the generation of the R-tree index broadcast schedule. If they have high frequencies, we allocate them serially on the single channel. If they have low frequencies, we allocate them in parallel on the multiple channels. As a result, we can reduce the index node access conflicts and the long broadcast cycle. The performance evaluation shows that our scheme gives the better performance than the existing schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.450-457
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• 2008

One of very essential techniques for enlarging lifetime of energy-constrained wireless personal area network (WPAN) devices is energy-efficient transmission technique. If the WPAN is operated based on a TDMA protocol, the satisfaction of QoS requirements at each allocated time slot is another important factor to be considered. We therefore propose an energy-efficient transmission scheme for WPANs operating with a contention-free medium access protocol such as TDMA, as well as satisfying QoS requirement. The proposed algorithm determines the optimum combination of transmit power, physical data rate and fragment size required to simultaneously minimize the energy consumption and satisfy the required QoS in each assigned time duration, considering all the possible energy-minimization related parameters. The proposed algorithm demonstrated the improved performance results in terms of throughput and energy consumption via computer simulation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.7
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• pp.303-312
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• 2006

This paper proposes the architecture and protocol of a data communication network for the safety system in nuclear power plants. First, we establish four design criteria with respect to determinability, reliability, separation and isolation, and verification/validation. Next we construct the architecture of the safety network for the following systems: PPS (Plant Protection System), ESF-CCS (Engineered Safety Features-Component Control System) and CPCS (Core Protection Calculator System). The safety network consists of 12 sub-networks and takes the form of a hierarchical star. Among 163 communication nodes are about 1600 origin-destination (OD) pairs created on their traffic demands. The OD pairs are allowed to exchange data only during the pre-assigned time slots. Finally, the communication protocol is designed in consideration of design factors for the safety network. The design factors include a network topology of star, fiber-optic transmission media, synchronous data transfer mode, point-to-point link configuration, and a periodic transmission schedule etc. The resulting protocol is the modification of IEEE 802.15.4 (LR-WPAN) MAC combined with IEEE 802.3 (Fast Ethernet) PHY. The MAC layer of IEEE 802.15.4 is simplified by eliminating some unnecessary (unctions. Most importantly, the optional TDMA-like scheme called the guaranteed time slot (GTS) is changed to be mandatory to guarantee the periodic data transfer. The proposed protocol is formally specified using the SDL. By performing simulations and validations using Telelogic Tau SDL Suite, we find that the proposed safety protocol fits well with the characteristics and the requirements of the safety system in nuclear power plants.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1665-1676
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• 2001

The effect of spreading gain control on the throughput of a CDMA slotted ALOHA system is considered. Mobile users transmit packets over a shared channel, and the packets transmitted in the same time slot over the shared channel act as simultaneous access interference (SAI). When using spread-spectrum signal, a CDMA slotted ALOHA channel achieves high probability of capture due to the property of high title resolution, and the bit rate of user information is determined by spreading gain. When the SAI level gets larger, the high value of spreading gain enhances the packet throughput by increasing the probability of a successful packet transmission, while it degrades the of the effective throughput by reducing the user information bits carried within a packer. To solve the problem, we investigated the effect of the capture probability and the SAI level on these system throughputs, and evaluated the throughput performance of the system for each spreading gain control scheme. The results showed that the maximum effective throughput could be achieved with an unified method despite the variation of the SAI level by deriving an optimal value of the spreading gain according to 171e system states.

• Journal of Internet Computing and Services
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• v.8 no.4
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• pp.41-49
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• 2007

Ethernet passive optical network(EPON) is the next-generation technology for supporting services of high-quality at low-cost. In the EPON, all optical network units(ONUs) have to share a limited uplink channel for upstream data. In order to satisfy bandwidth demands of users on high-capacity local access networks(LANs), the optical line terminal(OLT) efficiently divides and allocates time slots of uplink channel to all ONUs. We discuss previous schemes for dynamic bandwidth allocation(DBA), such as interleaved polling with adaptive cycle time(IPACT) and sliding cycle time(SLICT). In this paper, dynamic right sizing of maximum-windows(DRSM), as a novel bandwidth allocation service, is proposed for more effective and efficient time slot allocation of the uplink channel. DRSM which is based on past information of bandwidth allocated by OLT calculates maximum available bandwidth and dynamically alters the maximum window size for the next ONU. This scheme does not only exert every effort to meet bandwidth demands of ONUs with the possible scope, it also seeks fairness of bandwidth allocation among ONUs.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.4
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• pp.198-205
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• 2005

In this paper, the miniaturization of aperture-coupled RHCP patch antenna for the GPS system is treated. Circularly polarization characteristics is implemented by truncating diagonal corners of the square patch. Antenna size is reduced by inserting four uniform slits at the patch edges, which was equivalently lengthened the surface current by meandering it, This antenna uses aperture-coupled feeding structure with crossed-slot shape in order to give easy miniaturization of RHCP patch antenna. Simulated and measured results show that $42.7\%$ lower antenna size is obtained, and also $56\%$ lower -10dB bandwidth and $38.5\%$ lower 3dB AR bandwidth are obtained. when the proposed design scheme is applied to a commercial GPS antenna structure, $42.9\%$ lower patch size and $56\%$ lower 3dB AR bandwidth compared to commercial antenna at the same frequency are obtained.

• Journal of the Semiconductor & Display Technology
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• v.19 no.1
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• pp.79-84
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• 2020

Unlike a printing process, it is difficult to pattern organic thin films in the longitudinal (coating) direction using a coating process. In this paper, we have investigated the feasibility of patterning organic thin films using needles. To this end, we have slot-coated an aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution in the form of a fine stripe or large area and then applied the dual needle; one for discharging the main solvent of the underlying thin film and the other for sucking the dissolved thin film. We have found that the pattern width and depth increase as the moving speed of the plate decreases. However, it is observed that the sidewall slope is very gentle (the length of the slope is of the order of 200 ㎛) due to the fact that the discharged main solvent is widely spread and then isotropic etching occurs. With this scheme, we have also demonstrated that a fine stripe can be obtained by scanning the dual needle closely. To demonstrate its applicability to solution-processable organic light-emitting diodes (OLEDs), we have also fabricated OLED with the patterned PEDOT:PSS stripe and observed the insulation property in the strong light-emitting stripe.

• Journal of radiological science and technology
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• v.33 no.3
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• pp.269-276
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• 2010

This study attempts to propose ways to optimize and improve the period of hospitalization for the radioiodine treatment by calculating the dose rate of patients treated with high-dose radioiodine by distance and time slot. As a result, 24 hours after the patient was treated with 100 mCi high-dose iodine, the dose rate was attenuated to $1,035{\mu}Sv/hr$ at the navel, to $109{\mu}Sv/hr$ at 50 cm, and to $33{\mu}Sv/hr$ at 100 cm. 24 hours after the patient was treated with 150 mCi high-dose iodine, the dose rate was attenuated to $637{\mu}Sv/hr$ at the navel, to $100{\mu}Sv/hr$ at 50 cm, and to $40{\mu}Sv/hr$ at 100 cm. 24 hours after the patient was treated with 180 mCi high-dose iodine, the dose rate was attenuated to $1,251{\mu}Sv/hr$ at the navel, $140{\mu}Sv/hr$ at 50 cm, and to $56{\mu}Sv/hr$ at 100 cm. In light of the current criterion for discharge recommended by the US Nuclear Regulatory Commission being $70.4{\mu}Sv/hr$, the present study indicates earlier discharge is feasible by applying a new scheme. This suggests that the proposed scheme in this study will help to solve the problem of shortage of treatment beds with the increasing trend of patients with thyroid cancer taken into consideration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.918-927
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• 2004

WCDMA system is 3rd generation wireless mobile system specified by 3GPP. In WCDMA downlink, two power control schemes are operated. One is inner loop power control operated in every slot. Another is outer loop power control based on one frame time. Base station (BS) can estimate proper transmission power by these two power control schemes. However, because each MS's transmission power makes a severe effect on BS's performance, BS cannot give excessive transmission power to the specific user. 3GPP defined Power Control Dynamic Range (PCDR) to guarantee proper BS's performance. In this paper, we propose Adaptive PCDR algorithm. By APCDR algorithm, Radio Network Controller (RNC) can estimate each MS's current state using received signal to interference ratio (SIR). APCDR algorithm changes MS's maximum code channel power based on frame. By proposed scheme, each MS can reduce wireless channel effect and endure outages in cell edge. Therefore, each MS can obtain better QoS. Simulation result indicate that APCDR algorithm show more attractive output than fixed PCDR algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.39-47
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• 2005

The range of hardware implementation increases in communication systems as high-speed processing is required for high data rate. In the broadband wireless access (BWA) system based on IEEE standard 802.16 the functions of higher part in the MAC layer to Provide data needed for generating MAC PDU are implemented in software, and the tasks from formatting MAC PDUs by using those data to transmitting the messages in a modem are implemented in hardware. In this paper, the interface hardware for efficient message exchange between MAC and PHY layers in the BWA system is designed. The hardware performs the following functions including those of the transmission convergence(TC) sublayer; (1) formatting TC PDU(Protocol data unit) from/to MAC PDU, (2) Reed-solomon(RS) encoding/decoding, and (3) resolving DL MAP and UL MAP, so that it controls transmission slot and uplink and downlink traffic according to the modulation scheme of burst profile. Also, it provides various control signal for PHY modem. In addition, the truncated binary exponential backoff (TBEB) algorithm is implemented in a subscriber station to avoid collision on contention-based transmission of messages. The VLSI architecture performing all these functions is implemented and verified in VHDL.