• Journal of IKEEE
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• v.16 no.4
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• pp.316-321
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• 2012

In this paper, we study the energy-efficient deployment strategy for micro base station (BS) in wireless cellular systems. Firstly, we formulate a general problem pertaining to total energy consumption minimization with the requirement of area spectral efficiency (ASE). We start from an observation about the correlation between the area covered by an additional micro BS and the increment of ASE. Under such an observation, we propose an efficient greedy micro BS deployment algorithm. Simulations show that the proposed deployment algorithm can deploy micro BSs with a slight performance reduction comparing with the optimal solution.

• Journal of the Korea Society of Computer and Information
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• v.15 no.6
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• pp.49-56
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• 2010

In this paper, a joint PHY-MAC layer optimized resource allocation scheme for OFDMA based micro base stations is investigated. We propose cross-layer optimized two-stage resource allocation scheme including cross-layer functional description and control information flow between PHY-MAC layers. The proposed two-stage resource allocation scheme consists of a user grouping stage and a resource allocation stage. In the user grouping stage, users are divided into a macro base station user group and a micro base station user group based on the PHY-MAC layer characteristics of each user. In the resource allocation stage, a scheduling scheme and an allotment of resources are determined. In the proposed scheme, diversity and adaptive modulation and coding (AMC) schemes are exploited as schedulers. Simulation results demonstrate that the proposed scheme increases the average cell throughput about 40~80 % compared to the conventional system without micro base stations.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1235-1240
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• 2005

This paper supposes the perfect power control at micro-cell and macro-cell. Under this supposition, we calculate SIR and decide the call admission by SIR. When we calculate SIR, we use the ratio of the power received the base station of micro-cell and the power received the base station of macro-cell. We analysis the performance of the system by the computer simulation while changing the ratio of power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2298-2319
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• 1999

In this paper, we propose a new moving mobile base station (MMBS) scheme for very low power and micro-size RMIMS (radio-interfaced micro information monitoring system) terminals. RMIMS terminals can be used in various application service areas such as pollution monitoring, environment surveillance, traffic monitoring, emergency monitoring (e.g., building, bridge, railroad breakdown), security monitoring (e.g., theft, alarm) and military application. For these applications based on wireless transmission technologies, sensor type RMIMS terminals must satisfy low cost and low power design (e.g., solar power, life limited battery) requirement. In RMIMS terminal design, this low power requirement limits transmission range of uplink or reverse link and means small cell size. Also these applications using RMIMS terminals may have a little bit non real-time traffic characteristic and low scattering density in service area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.203-208
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• 2005

To solve the cost problem of micro/picocell system, the fiber-optic cellular system was proposed. In this system, all channel elements are managed in Central Station, not in each base station. Also, all channel elements in a system can be dynamically assigned when the Spectrum Delivery Switch (SDS) is used. In this paper, we propose and analyze a new intergroup handoff scheme in the fiber-optic cellular system. The proposed scheme supports handoff with keeping current channel. Performance is evaluated with respect to the blocking probability and the handoff refused probability in both systems with SDS and without SDS. The numerical results show that the proposed scheme provides better performance than conventional soft handoff scheme.

• Journal of Integrative Natural Science
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• v.6 no.1
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• pp.12-15
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• 2013

To combine the micro rain radar and microwave radiometer cloud liquid water, we estimate the cloud physical thickness from the difference between the MTSAT-1R cloud top height and cloud base height of visual observation of Daegwallyeong weather station, and the cloud liquid water path of micro rain radar is obtained by multiplying the liquid water content of micro rain radar and the estimated cloud physical thickness. The trend of microwave radiometer liquid water path agrees with that of the micro rain radar during small precipitation. We study these characteristics of micro rain radar and microwave radiometer for small precipitation to obtain the combined cloud water content of micro rain radar and microwave radiometer, constantly operated regardless to the rainfall.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.1018-1024
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• 2001

In this paper, an array antenna is designed far base station of a street micro-cell in urban areas. It has a rectangular radiation pattern. The current distribution of the array is decided by using a modified Woodward-Lawson sampling pattern synthesis method. To confirm the realization of the array antenna with rectangular pattern, 12 array antenna with a planar type monopole fed by stripline is fabricated and measured. In the results of the measured values, H-plane pattern of the antenna nearly yields a rectangular radiation pattern.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.83-86
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• 2021

비디오 컨텐츠 사용이 증가하면서, 사용자가 요구한 파일을 제시간 안에 전달하는 문제가 중요해졌다. 사용자와 가까운 곳에 파일을 캐싱해 두고 필요할 때 다운받으면 파일을 보다 빨리 전달할 수 있는데 사용자가 움직일 경우 이동성을 고려해야 한다. 본 논문에서는 사용자의 이동 경로와 파일의 인기도를 함께 고려해 딜레이드 오프로딩(delayed offloading) 스키마를 적용한 환경에서 마이크로 기지국(micro base station, MBS)에서 다운받는 데이터 크기를 최소로 만들어 비용을 최소화 하는 캐싱 기법을 제안한다. 실험을 통해 타알고리즘에 비해 MBS 로부터 다운받는 양을 줄이고 스몰 셀 기지국(small cell base station, SBS)에서 다운받을 성공 확률을 높이는데 효과가 있다는 것을 보였다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.10a
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• pp.321-333
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• 2005

With the limited frequency spectrum and an increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. However, finding a conflict free channel assignment with the minimum channel span is NP hard. As demand for services has expanded in the cellular segment, sever innovations have been made in order to increase the utilization of bandwidth. The innovations are cellular concept, dynamic channel assignment and hierarchical network design. Hierarchical network design holds the public eye because of increasing demand and quality of service to mobile users. We consider the frequency assignment problem and the base station placement simultaneously. Our model takes the candidate locations emanating from this process and the cost of assigning a frequency, operating and maintaining equipment as an input. In addition, we know the avenue and demand as an assumption. We propose the network about the profit maximization. This study can apply to GSM(Global System for Mobile Communication) which has 70% portion in the world. Hierarchical network design using GA(Genetic Algorithm) is the first three-tier (Macro, Micro, Pico) model, We increase the reality through applying to EMC (Electromagnetic Compatibility Constraints). Computational experiments on 72 problem instances which have 15${\sim}$40 candidate locations demonstrate the computational viability of our procedure. The result of experiments increases the reality and covers more than 90% of the demand.

• Smart Structures and Systems
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• v.14 no.4
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• pp.617-641
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• 2014

The energy constraint is still a common issue for the practical application of wireless sensors, since they are usually powered by batteries which limit their lifetime. In this paper, a practical compound energy efficiency strategy is proposed and realized in the implementation of a real time wireless sensor platform. The platform is intended for wireless structural monitoring applications and consists of three parts, wireless sensing unit, base station and data acquisition and configuration software running in a computer within the Matlab environment. The high energy efficiency of the wireless sensor platform is achieved by a proposed adaptive radio transmission power control algorithm, and some straightforward methods, including adopting low power ICs and high efficient power management circuits, low duty cycle radio polling and switching off radio between two adjacent data packets' transmission. The adaptive transmission power control algorithm is based on the statistical average of the path loss estimations using a moving average filter. The algorithm is implemented in the wireless node and relies on the received signal strength feedback piggybacked in the ACK packet from the base station node to estimate the path loss. Therefore, it does not need any control packet overheads. Several experiments are carried out to investigate the link quality of radio channels, validate and evaluate the proposed adaptive transmission power control algorithm, including static and dynamic experiments.