• Journal of the Korea Society of Computer and Information
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• v.21 no.12
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• pp.73-79
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• 2016

This paper proposes a novel resource allocation scheme which enables to guarantee the quality of experience (QoE) for handovers from femtocell to macrocell and vice versa, and between femtocells in the overlaid macro-femto networks. The proposed scheme guarantees QoE to a certain extent during handover by utilizing a fixed amount of radio resource reserved in advance for the dedicated use to support QoE. We take both the type of the handover and the temporal sensitiveness characteristics of user services into consideration in order to support QoE. Performance of our scheme is analyzed by simulation with respect to the outage probability and total throughput.

• ETRI Journal
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• v.34 no.3
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• pp.297-307
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• 2012

A femtocell is a small cellular base station, typically designed for use in a home or small business. The random deployment of a femtocell has a critical effect on the performance of a macrocell network due to co-channel interference. Utilizing the advantage of a multiple-input multiple-output system, each femto base station (FBS) is able to form a cluster and generates a precoding matrix, which is a modified version of conventional single-cell block diagonalization, in a cooperative manner. Since interference from clustered-FBSs located at the nearby macro user equipment (MUE) is the dominant interference contributor to the coexisting networks, each cluster generates a precoding matrix considering the effects of interference on nearby MUEs. Through simulation, we verify that the proposed algorithm shows better performance respective to both MUE and femto user equipment, in terms of capacity.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.81-84
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• 2018

Recently, many researchers claim that mobile data offloading is a key solution to alleviating overloaded cellular traffic by dividing the overloaded traffic with femtocells, WiFi networks or users. In this paper, we propose an idea to select a group of users, known as VIPs, that is able to effectively transfer the data to others using Density-Based Spatial Clustering of Application with Noise, also known as DBSCAN algorithm. We conducted our experiments using NCCU real trace dataset. The results show that our proposed idea offload about 70~77% of the network with VIP set size of four, which is better than the compared methods.

• ETRI Journal
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• v.40 no.6
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• pp.726-735
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• 2018

Femtocells are good examples of the ultimate networking technology, offering enhanced indoor coverage and higher data rate. However, the dense deployment of femto base stations (FBSs) and the exploitation of subcarrier reuse between macrocell base stations and FBSs result in significant co-tier and cross-tier interference, thus degrading system performance. Therefore, appropriate resource allocations are required to mitigate the interference. This paper proposes a discrete bacterial foraging optimization (DBFO) algorithm to find the optimal resource allocation in two-tier networks. The simulation results showed that DBFO outperforms the random-resource allocation and discrete particle swarm optimization (DPSO) considering the small number of steps taken by particles and bacteria.

• International Journal of Computer Science & Network Security
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• v.22 no.4
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• pp.27-32
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• 2022

The fifth generation (5G) mobile communication technology is designed to meet all communication needs. Heterogeneous networks (HetNets) are a new emerging network structure. HetNets have greater potential for radio resource reuse and better service quality than homogeneous networks since they can evolve small cells into macrocells. Effective resource allocation techniques reduce inter-user interference while optimizing the utilization of limited spectrum resources in HetNets. This article discusses resource allocation in 5G HetNets. This paper explains HetNets and how they work. Typical cell types in HetNets are summarized. Also, HetNets models are explained in the third section. The fourth component addresses radio resource control and mobility management. Moreover, future study in this subject may benefit from this article's significant insights on how HetNets function.

• Electronics and Telecommunications Trends
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• v.25 no.5
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• pp.72-83
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• 2010

통신시장의 경쟁 심화, 소비자 요구 다양화, 통신비 부담 증가와 더불어 유무선 통신 기술 발달로 유무선 융합 서비스의 출현이 기대되어 2007년부터 펨토셀이 각광받기 시작했다. 유무선사업자에 대한 이동통신 사업자의 경쟁력 강화와 신규 수익 모델 창출 방안으로 이동통신 전화 중심의 유무선 융합 기술인 펨토셀이 부상된 것이다. 펨토셀(Femtocells)은 가정이나 사무실 등 실내에서 사용되는 초소형 이동통신용 기지국으로서, 음영지역을 해소하는 대안이며, 유무선 컨버전스 서비스를 위한 실내 통신 인프라로 활용할 수 있다는 점에서 전 세계 통신업체들의 관심이 높아지고 있다. 한편 이동통신 모뎀이 3G WCDMA에서 4G LTE/LTE-Adv.로 급속히 변경될 것으로 예측되고 있다. 펨토셀이 음영지역을 대체하는 효과만으론 시장활성화가 급속하게 이루어지지 않았으나, 4G 이동통신으로 넘어가면서 LTE 펨토셀 보급도 급물살을 탈 것으로 예측된다. 그 이유는 LTE가 패킷데이터 전송에 기반을 둔 다양한 서비스 지원이 가능한 이동통신으로서 하향링크 최대 전송속도 300Mbps peak data rate가 가능하기 때문이다. 휴대셋에서 고속의 멀티미디어 서비스가 가능해 질 수 있음을 시사하는 것이다. 본보고서는 LTE 기반 펨토셀 구조를 살펴보고, 표준화동향 및 산업체 동향을 살펴보고자 한다.

• ETRI Journal
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• v.40 no.3
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• pp.318-329
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• 2018

Femtocell (FC) technology envisaged as a cost-effective approach to attain better indoor coverage of mobile voice and data service. Deployment of FCs over macrocell forms a heterogeneous network. In urban areas, the key factor limits the successful deployment of FCs is inter-cell interference (ICI), which severely affects the performance of victim users. Autonomous FC transmission power setting is one straightforward way for coordinating ICI in the downlink. Application of intelligent control using soft computing techniques has not yet explored well for wireless networks. In this work, autonomous FC transmission power setting strategy using Adaptive Neuro Fuzzy Inference System is proposed. The main advantage of the proposed method is zero signaling overhead, reduced computational complexity and bare minimum delay in performing power setting of FC base station because only the periodic channel measurement reports fed back by the user equipment are needed. System level simulation results validate the effectiveness of the proposed method by providing much better throughput, even under high interference activation scenario and cell edge users can be prevented from going outage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4871-4877
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• 2015

This article presents a circuit and a system for IEEE 1588 based clock synchronization to generate a very accurate frequency signal required in femtocell devices. A prototype board and the experimental environment to verify the functions and to evaluate the performance are explained to verify the feasibility of the proposed synchronization system. To make low-cost femtocells without constraints on the place of installation, it is very important to study on the practical implementation of synchronization system based on IEEE 1588. The experimental result shows that the synchronization errors between -16 ns and 9 ns are guaranteed over the network of femtocell devices with the proposed synchronization circuits, thus the synchronization criteria of the 3GPP HNB are met.

• Journal of Information Processing Systems
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• v.5 no.4
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• pp.207-220
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• 2009

A large number of phone calls and data services will take place in indoor environments. In Long Term Evolution (LTE), femtocell, as a home base station for indoor coverage extension and wideband data service, has recently gained significant interests from operators and consumers. Since femtocell is frequently turned on and off by a personal owner, not by a network operator, one of the key issues is that femtocell should be identified autonomously without system information to support handover from macrocell to femtocell. In this paper, we propose a dynamic reservation scheme of Physical Cell Identities (PCI) for 3GPP LTE femtocell systems. There are several reserving types, and each type reserves a different number of PCIs for femtocell. The transition among the types depends on the deployed number of femtocells, or the number of PCI confusion events. Accordingly, flexible use of PCIs can decrease PCI confusion. This reduces searching time for femtocell, and it is helpful for the quick handover from macrocell to femtocell. Simulation results show that our proposed scheme reduces average delay for identifying detected cells, and increases network capacity within equal delay constraints.

• Journal of Advanced Navigation Technology
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• v.16 no.3
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• pp.471-479
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• 2012

In cellular femto systems, femto Base stations(f-BSs) can be installed unnecessarily and overcrowded in small areas. This will cause an interference problem and it can impact on the capacity, blocking probability, and coverage of femtocells in the shared channel systems. In this paper, we propose a load distribution scheme by using forced handover and probabilistic subchannel scheduling policy to resolve the problem. The proposed scheme operates in distributed manner though communication with neighboring f-BSs, and includes self-detection of overcrowded area and radio resource management based on measurements. We evaluate the performance of the proposed scheme in terms of average cell throughput and average throughput per users.