• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.905-914
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• 2006

For an accurate rainfall-runoff simulation in the river basin, not evaluation of runoff model but accurate runoff data are very important. In this study, SSARR model was applied to the Geum River basin and these results are compared with runoff data observed at the Gongju gauging station. The model results didn't good fit the discharge data determined from the rating curve at Gongju gauging station during normal and dry season, especially. For the reliability analysis for the existing rating curve, we observed new stream discharge set from 2003 to 2005. We also estimated long term runoff data from the base flow separation method and defined the hydraulic characteristics. The results show that the new observed stream discharge is similar to the rainfall-runoff model results but existing rating curve seems to be overestimated about 10-20% during normal and dry season. We found that the continuous monitoring and update for the existing rating curve at the gaging station are needed for accurate estimation of runoff data.

• ETRI Journal
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• v.42 no.1
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• pp.26-35
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• 2020

Herein, we consider uplink multiuser massive multiple-input multiple-output systems when multiple users transmit information symbols to a base station (BS) by applying simple space-time block coding (STBC). At the BS receiver, two detection filters for each user are used to detect the STBC information symbols. One of these filters is for odd-indexed symbols and the other for even-indexed symbols. Using constrained output variance metric minimization, we first derive a special relation between the closed-form optimal solutions for the two detection filters. Then, using the derived special relation, we propose a new blind adaptive algorithm for implementing the minimum output variance-based optimal filters. In the proposed adaptive algorithm, filter weight vectors are updated only in the region satisfying the special relation. Through a theoretical analysis of the convergence speed and a computer simulation, we demonstrate that the proposed scheme exhibits faster convergence speed and lower steady-state bit error rate than the conventional scheme.

• Journal of Korea Multimedia Society
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• v.21 no.5
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• pp.592-598
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• 2018

In wireless sensor networks where there is no centralized base station, each node has limited transmission range and the multi-hop routing for transmitting data to the destination is the one of the important technical issues. In particular, the wireless sensor network is not powered by external power source but operates by its own battery, so it is required to maximize the network life through efficient use of energy. To balance the power consumption, the residual power based adaptive power control is required in routing protocol. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes by controlling the transmit power according to the residual power. We evaluate the proposed routing protocol using extensive simulation, and the results show that the proposed routing scheme can balance the power consumption and prolong network lifetime.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3394-3408
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• 2014

Conventional mobile state (MS) and base station (BS) association based on average signal strength often results in imbalance of cell load which may require more powerful processor at BSs and degrades the perceived transmission rate of MSs. To deal with this problem, a Markov decision process (MDP) for load balancing in a multi-cell system with multi-carriers is formulated. To solve the problem, exploiting Sarsa algorithm of on-line learning type [12], ${\alpha}$-controllable load balancing algorithm is proposed. It is designed to control tradeoff between the cell load deviation of BSs and the perceived transmission rates of MSs. We also propose an ${\varepsilon}$-differential soft greedy policy for on-line learning which is proven to be asymptotically convergent to the optimal greedy policy under some condition. Simulation results verify that the ${\alpha}$-controllable load balancing algorithm controls the behavior of the algorithm depending on the choice of ${\alpha}$. It is shown to be very efficient in balancing cell loads of BSs with low ${\alpha}$.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.140-145
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• 2008

We recently developed new offshore observation system using USN buoy, widely used to measure the directional properties of ocean wave, seawater temperature, UV light, longitude and latitude of the buoy using GPS module. This paper also documents the development and implementation of a buoy network for acquisition of data of base station with buoys. The major phases of the project include specification of the network, physical construction of network nodes, software development for control of nodes, and testing of network performance. We described some of the practical issues involved in designing, building and deploying a buoy network for oceanographic monitoring. The paper explains some of the design decisions and their consequences, and some of the lessons learned from a first lesson network trial at sea.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.205-206
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• 2008

We propose load balancing algorithm based on cross layer designing for MIMO OFDM system. When there are many users using data service, base station(BS) should distribute traffic. Moreover, cross layer design gives benefit managing radio resource and network bandwidth management. Proposed cross layer load balancing technique manages both BS's bandwidth allocation and MS’s power control. One BS request bandwidth to other BSes and other BSes reduce each bandwidth. And BSes reduce power of sub carriers for reserving available bandwidth of backhaul. MSes that didn't get service can be served by obtaining bandwidth from other BSes. The simulation result shows more users can be served and cell throughput was increased

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.2043-2060
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• 2020

Developed from Digital Multimedia Broadcasting (DMB), DMB+ changes the application focus fundamentally. The plus symbol "+" indicates that DMB+ is no longer for digital radio/videos, instead it works as a general data transmission technique. The merits of wireless transmission, broad coverage, high quality, information security and low building/maintenance cost make DMB+ suitable for a wide range of applications with numerous terminals and users, such as public information release, alarm and administration etc. The concept of DMB+ base station enables DMB+ to be used in building independent networks and for remote control and management, as well as for Industry 4.0. DMB+ will access into a new field that till now has been dominated by communication techniques, will open a huge commercial opportunity.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.104-107
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• 2003

본 논문에서는 VHF대역 기지국용 전력증폭기에 대해 입력레벨이 $0dBm{\pm}1 dB$, 출력이 $45dBm{\pm}1dB$인 증폭기를 모듈화 하여 설계하고 제작 및 측정하였다. 출력 레벨 제어는 Pin Diode 감쇄기를 이용하여 Dynamic Range 40dB 내에서 5단계로 전력제어가 가능하고 입력레벨이 $-4{\sim}0dBm$로 변동될 때 AGC(Auto Gain Control) 회로가 동작 되도록 설계하였다.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.660-664
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• 2010

This paper proposes a backoff control scheme for guaranteeing fair packet transmissions in TDMA wireless networks. In order to maximize the system performance, the number of packets transmitted in a frame should be kept at a proper level. In the proposed scheme, the base station calculates the packet transmission probability according to the offered loads and then broadcasts to all the mobile stations. Mobile stations attempt to transmit a packet with the received probability. Simulation results show that the proposed scheme can offer better system throughput and delay performance than the conventional one regardless of the offered loads.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1367-1370
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• 2005

무선 센서 네트워크에서 제안된 혼잡을 회피한 TDMA 기반의 MAC 프로토콜은 많은 노드에서 한꺼번에 전송할 데이터가 발생하더라도 중간에서 전달하는 노드가 타임슬롯을 소스 노드의 타임슬롯을 선택함으로써 혼잡에 의한 지연 없이 데이터를 BS(base station)으로 전달할 수 있다. 하지만, 데이터를 전달받기 위해서는 모든 타임슬롯에 걸쳐서 idle listening 을 수행하여야 하므로 에너지 소비가 크다. 본 논문은 혼잡을 회피한 TDMA 기반의 MAC 프로토콜로써 전원 제어 패킷(power control packet)을 이용하여 데이터의 전달을 이웃 노드에게 예측할 수 있도록 함으로써 노드들로 하여금 수면 모드로의 전환이 가능하게 되어 각 노드의 에너지가 절감된다.