• Smart Media Journal
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• v.13 no.1
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• pp.52-59
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• 2024

This paper proposes a plan to improve the reception radio environment of the mobile terminal and maintain a constant reception electric field by using small cells in a small closed environment. In order to configure an efficient communication infrastructure for small cells, both ends of wireless transmission and reception of an Ethernet-based wireless video recording system are connected using an L2 switch. The small cell connected to the receiving side L2 switch shares the wireless network section of the wireless video recording system and connects to the transmitting side L2 switch. After that, when it is normally linked to FMS, a management system for small cells, through the Internet network, the output of small cells is checked. In order to verify the results, a proposed network is formed on the elevator inside the building with a poor radio wave environment, and the radio wave environment is measured before and after the small cell application in the section where the elevator operates. As a result, the main parameters of the radio wave environment in all sections of the elevator are improved, as well as a constant receiving electric field strength within the moving elevator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.5
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• pp.280-292
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• 2014

Recently, heterogeneous networks consisting of small-cells on top of traditional macro-cellular network has attracted much attention, because traditional macro-cellular network is not suitable to support more demanding mobile data traffic due to its limitation of spatial reuse. However, due to the transmit power difference between macro- and small-cells, most users are associated with macro-cells rather than small-cells. To solve this problem, enhanced inter-cell interference coordination (eICIC) has been introduced. Particularly, in eICIC, the small-cell coverage is forcibly expanded to associate more users with small-cells. Then, to avoid cross-tier interference from macro-cells, these users are allowed to receive the data during almost blank subframe (ABS) in which macro-cells almost remain silent. However, this approach is not sufficient to balance the load between macro- and small-cells because it only expands the small-cell coverage. In this paper, we propose a load balance scheme improving proportional fairness for heterogeneous networks employing eICIC. In particular, the proposed scheme combines the greedy-based user association and the ABS rate determination in a recursive manner to perform the load balance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1518-1520
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• 2015

This letter considers a problem of associating users to small-cell base stations (sBSs) and selecting a set of operating sBSs in a small-cell network to minimize the power consumption. We derive a message passing algorithm to obtain a solution distributively. Simulation results show that the proposed algorithm is superior to the conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2539-2548
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• 2015

Overcoming inter-cell interference and spectrum scarcity are major issues in heterogeneous cellular networks. Static Frequency reuse schemes have been proposed as an effective way to manage the spectrum and reduce ICI(Inter cell Interference) in cellular networks. In a kind of static frequency reuse scheme, the allocations of transmission power and subcarriers in each cell are fixed prior to system deployment. This limits the potential performance of the static frequency reuse scheme. Also, most of dynamic frequency reuse schemes did not consider small cell and the network environment when the traffic load of each cell is heavy and non-uniform. In this paper, we propose an inter-cell resource allocation algorithm that dynamically optimizes subcarrier allocations for the multi-cell heterogeneous networks. The proposed dynamic frequency reuse scheme first finds the subcarrier usage in each cell-edge by using the exhaustive search and allocates subcarrier for all the cells except small cells. After that it allocates subcarrier for the small cell and then iteratively repeats the process. Proposed dynamic frequency reuse scheme performs better than previous frequency reuse schemes in terms of the throughput by improving the spectral efficiency due to it is able to adapt the network environment immediately when the traffic load of each cell is heavy and non-uniform.

• The Magazine of the IEIE
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• v.41 no.12
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• pp.43-51
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• 2014

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.83-90
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• 2013

• Information and Communications Magazine
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• v.31 no.11
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• pp.79-86
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• 2014

지속되는 무선 데이터 트래픽 증가 추세의 대처 방안 중 새로운 주파수 발굴에는 많은 시간과 비용이 수반되어, 이를 해결하기 위한 방안으로 유럽 및 미국에서 주파수 공동 사용의 도입이 추진되고 있다. 주파수 공동 사용은 둘 이상의 주파수 이용자가 특정 주파수를 공동 사용 조건에 따라 사용하는 것을 의미하며, 지역, 시간에 따라 제한적으로 사용하고 있는 공공용 주파수 대역을 활용할 계획이다. 현재 유럽은 2.3 GHz 대역, 미국은 3.5 GHz 대역을 스몰 셀로 주파수 공동 활용하기 위해 제도 정비 및 표준화를 추진 중이다. 이러한 국제적인 활용 동향은 향후 해당 대역의 국내 활용 방안 정립에 참고가 될 수 있을 것으로 보인다.

• Journal of Convergence Society for SMB
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• v.6 no.3
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• pp.21-27
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• 2016

In this paper, we introduce the PB/MC-CDMA (Partial Block/Multi-Carrier-Code Division Multiple Access) system to mitigate inter-cell interference (ICI) and enhance user capacity in the small cell environment. In 5G mobile communications, the number of devices connected to the network is expected to increase exponentially with the expansion of the IoT (Internet of Things) services. In addition, each device is expected to be required by the various data rates by their content types. In LTE/LTE-A, there are some limitations that large scale connectivity and supporting various data rates. Therefore, we introduce a PB/MC-CDMA physical layer system which is suitable for the small cell environment, and evaluate the performance in the multi cell environment which is affected by ICI. Through computer simulation results, we demonstrate the effectiveness of PB/MC-CDMA for the small cell environment.

• KIPS Transactions on Computer and Communication Systems
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• v.7 no.8
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• pp.203-210
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• 2018

Mobile traffic is increasing consistently, and mobile carriers are becoming more and more hard to meet this ever-increasing mobile traffic demand by means of additional installation of base stations. To overcome this problem, heterogeneous networks, which can reuse space and frequency by installing small cells such as femto cells in existing macro cells, were introduced. However, existing macro cell users are difficult to increase the spectral efficiency without the cooperation of femto owners. Femto owners are also reluctant to accommodate other mobile stations in their femto stations without proper incentive. In this paper, a method of obtaining the optimal incentive is proposed, which adopts a utility function based on the logarithm of throughput of mobile stations, and the incentive is calculated to maximize the utility of the entire network.

• 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.