• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.9-17
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• 2014

Heterogeneous network (HetNet) is a network consisting of macrocells overlaid with small cells. In HetNet, the interference from macrocell to small cell users is a major cause of performance degradation of small cell users and enhanced inter-cell interference coordination (eICIC) is needed to mitigate the interference. Previous works on eICIC gives limited performance gain because these works focus on maximizing long-term throughput and rarely consider varying channel conditions over frames. This paper proposes a new algorithm which dynamically coordinates interference and schedules users on each frame to maximize the total utility of the network with lower computational complexity than exhaustive search. Simulation results show that the proposed algorithm achieves higher total throughput than the throughput with the conventional algorithm, and has higher fairness index than the conventional algorithm when there large number of users.

• 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.

• Journal of Internet Computing and Services
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• v.22 no.6
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• pp.9-15
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• 2021

In ultra-dense heterogeneous networks, the amount of interference from small-cell base stations(SBS) to macro-cell user equipments (MUEs) increases significantly as the number of SBSs increases and it causes the MUEs to decrease the signal-to-interference and noise ratio(SINR) and system capacity. In this paper, we propose a small-cell based cooperative multi-point(CoMP) communication scheme that can guarantee the performance of MUEs even when the number of SBSs increases. In the proposed scheme, MUEs first find SBSs that give signal strength equal to or greater than a given SINR threshold and then they are served by different numbers of the selected SBSs using CoMP to improve the performance of MUEs. Simulation results show that the proposed small-cell based CoMP scheme outperforms other interference management or CoMP schemes in terms of the SINR and system capacity of MUEs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.12
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• pp.2806-2811
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• 2013

New technologies such as multi-antenna and small cell were proposed as key technology for the next generation mobile system to cope with the explosively increasing mobile data traffic. In particular, heterogeneous mobile communication network which can improve spatial reuse factor by exploiting macro and small cells simultaneously is attracting attention. However, the heterogeneous network has a problem that the utilization of small cells becomes low because the transmit power of macro base stations is much higher than that of small base stations and then the probability that mobile stations are attached to the macro base stations becomes high. This problem is dominant in uplink. The concept of cell range expansion bias to mitigate the problem was proposed by 3GPP and the corresponding standardization is in progress. In this paper, we analyze the downlink performance of the heterogeneous mobile communication network based on a system level simulator with the cell range expansion bias in terms of average cell spectral efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.277-288
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• 2013

3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced) as a next generation mobile communication standard introduced small base stations such as femto cells or pico cells, and D2D (Device-to-Device) communications between mobiles in the proximity in order to satisfy the needs of rapidly growing wireless data traffic. A diverse range of topics has been studied to solve various interference situations which may occur within a single cell. In particular, an introduction of a small base station along with D2D communication raises important issues of how to increase the channel capacity and frequency efficiency in HetNets (Heterogeneous Networks). To this end, we propose in this paper methods to manage the interference between the macro cell and other small cells in the HetNet to improve the frequency efficiency. The proposed CCN (Cluster Coordinator Node)-assisted ICI (Inter-Cell Interference) avoidance methods exploit the CCN to control the interference in HetNet comprising of an MeNB (Macro enhanced Node-B) and a large number of small cells. A CCN which is located at the center of a number of small cells serves to avoid the interference between macro cell and small cells. We propose methods of resource allocation to avoid ICI for user equipments within the CCN coverage, and evaluate their performance through system-level computer simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2397-2402
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• 2014

Recently, heterogeneous mobile communication network is attracting plenty of interest to serve explosively increasing mobile data traffic. Although the heterogeneous mobile communication network can enhance spatial reuse ratio by using both conventional macro cells and small cells simultaneously, it causes the unbalance in performance of downlink and uplink. In this paper, we propose a new cell selection scheme for heterogeneous mobile communication network. In the proposed cell selection scheme, mobiles select their home cells by considering both uplink and downlink performance, contrary to conventional schemes. We analyze the performance of the proposed scheme in terms of average cell transmission rate through system level simulations and compare it with those of conventional schemes.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.97-100
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• 1999

Mobile network applications are growing and this requires a fast and efficient transport method between the BS(Base Station) and the MSC(Mobile Switching Center). One possible solution is to use ATM and a voice CODEC standard which compresses 64kbps voice data to less than 8kbps. The low bit tate and small-sized packets made by the voice CODEC imply that significant amount of link bandwidth would be wasted, if this small-sized packet is carried by one ATM cell. The cell assembly delay increases if one ATM cell is fully filled with the small-sized packets. For the bandwidth-efficient transmission of low-rate, short, and variable length packets in delay sensitive applications, AAL-2 was standardized. This paper evaluates performance of AAL-2 by using voice CODEC standard.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4799-4818
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• 2015

In this paper, we investigate the problem of achieving global optimization for distributed carrier aggregation (CA) in small cell networks, using a game theoretic solution. To cope with the local interference and the distinct cost of intra-band and inter-band CA, we propose a non-cooperation game which is proved as an exact potential game. Furthermore, we propose a spatial adaptive play learning algorithm with heterogeneous learning parameters to converge towards NE of the game. In this algorithm, heterogeneous learning parameters are introduced to accelerate the convergence speed. It is shown that with the proposed game-theoretic approach, global optimization is achieved with local information exchange. Simulation results validate the effectivity of the proposed game-theoretic CA approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.1
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• pp.50-61
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• 2014

Operating small cell with existing macro cell is of interest in wireless communication technology to enhance network capacity. Closed-access small cell allows the access of users registered in it and causes severe interference to nearby users connected to macrocell. We propose a dynamic channel allocation for small cells in the same building that first aim to minimize call-drop of the nearby macrocell users, and then want to reduce interferences between the small cells. Since the interference effect of small cells on the nearby macrocell users mainly depends on the small cells' position, the proposed algorithm includes a self-configuration to flexibly allocate frequency channels according to the variation of downlink quality of the macrocell users. Furthermore the algorithm is very simple and practical, which is main contribution of this paper. We observe that the proposed algorithm provides 82-94% of maximum achievable throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5301-5323
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• 2017

Small cell deployment offers a low-cost solution for the boosted traffic demand in heterogeneous cellular networks (HCNs). Besides improved spatial spectrum efficiency and energy efficiency, future HCNs are also featured with the trend of network architecture convergence and feasibility for flexible mobile applications. To achieve these goals, dual connectivity (DC) is playing a more and more important role to support control/user-plane splitting, which enables maintaining fixed control channel connections for reliability. In this paper, we develop a tractable framework for the downlink SINR analysis of DC assisted HCN. Based on stochastic geometry model, the data-control joint coverage probabilities under multi-frequency and single-frequency tiering are derived, which involve quick integrals and admit simple closed-forms in special cases. Monte Carlo simulations confirm the accuracy of the expressions. It is observed that the increase in mobility robustness of DC is at the price of control channel SINR degradation. This degradation severely worsens the joint coverage performance under single-frequency tiering, proving multi-frequency tiering a more feasible networking scheme to utilize the advantage of DC effectively. Moreover, the joint coverage probability can be maximized by adjusting the density ratio of small cell and macro cell eNBs under multi-frequency tiering, though changing cell association bias has little impact on the level of the maximal coverage performance.