• Journal of Internet Computing and Services
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• v.22 no.5
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• pp.1-8
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• 2021

Small-cells in heterogeneous networks are one of the important technologies to increase the coverage and capacity in 5G cellular networks. However, due to the randomly arranged small-cells, co-tier and cross-tier interference increase, deteriorating the system performance of the network. In order to manage the interference, some channel management methods use fractional frequency reuse(FFR) that divides the cell coverage into the inner region(IR) and outer region(OR) based on the distance from the macro base station(MBS). However, since it is impossible to properly measure the distance in the method with FFR, we propose a new interference aware FFR(IA-FFR) method to enhance the system performance. That is, the proposed IA-FFR method divides the MUEs and SBSs into the IR and OR groups based on the signal to interference plus noise ratio(SINR) of macro user equipments(MUEs) and received signals strength of small-cell base stations(SBSs) from the MBS, respectively, and then dynamically assigns subchannels to MUEs and small-cell user equipments. As a result, the proposed IA-FFR method outperforms other methods in terms of the system capacity and outage probability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2595-2618
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• 2018

In this paper, we investigate secure communication with the presence of multiple eavesdroppers (Eves) in a two-tier downlink dense heterogeneous network, wherein there is a macrocell base station (MBS) and multiple femtocell base stations (FBSs). Each base station (BS) has multiple users. And Eves attempt to wiretap a macrocell user (MU). To keep Eves ignorant of the confidential message, we propose a physical-layer security scheme based on cross-layer cooperation to exploit interference in the considered network. Under the constraints on the quality of service (QoS) of other legitimate users and transmit power, the secrecy rate of system can be maximized through jointly optimizing the beamforming vectors of MBS and cooperative FBSs. We explore the problem of maximizing secrecy rate in both non-colluding and colluding Eves scenarios, respectively. Firstly, in non-colluding Eves scenario, we approximate the original non-convex problem into a few semi-definite programs (SDPs) by employing the semi-definite relaxation (SDR) technique and conservative convex approximation under perfect channel state information (CSI) case. Furthermore, we extend the frame to imperfect CSI case and use the Lagrangian dual theory to cope with uncertain constraints on CSI. Secondly, in colluding Eves scenario, we transform the original problem into a two-tier optimization problem equivalently. Among them, the outer layer problem is a single variable optimization problem and can be solved by one-dimensional linear search. While the inner-layer optimization problem is transformed into a convex SDP problem with SDR technique and Charnes-Cooper transformation. In the perfect CSI case of both non-colluding and colluding Eves scenarios, we prove that the relaxation of SDR is tight and analyze the complexity of proposed algorithms. Finally, simulation results validate the effectiveness and robustness of proposed scheme.

• The KIPS Transactions:PartB
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• v.17B no.4
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• pp.309-316
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• 2010

This paper introduces a new model based method for facial expression recognition that uses facial grid angles as feature space. In order to be able to recognize the six main facial expression, proposed method uses a grid approach and therefore it establishes a new feature space based on the angles that each gird's edge and vertex form. The way taken in the paper is robust against several affine transformations such as translation, rotation, and scaling which in other approaches are considered very harmful in the overall accuracy of a facial expression recognition algorithm. Also, this paper demonstrates the process that the feature space is created using angles and how a selection process of feature subset within this space is applied with Wrapper approach. Selected features are classified by SVM, 3-NN classifier and classification results are validated with two-tier cross validation. Proposed method shows 94% classification result and feature selection algorithm improves results by up to 10% over the full set of feature.

• Knowledge Management Research
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• v.9 no.2
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• pp.109-127
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• 2008

This cross-level study of 77 samples from Korean 1st-tier suppliers participating in knowledge-sharing networks examined the impact of partnering(joint establishment of goal and joint problem solving system) on supplier relationship outcomes(competativeness improvement and innovative idea suggestion). The findings showed that joint establishment of goal and joint problem solving system were positively related to both supplier's competativeness improvement and its innovative idea suggestion. Whereas, joint problem solving system did account for a significant variance only in innovative idea suggestion. The findings, further, demonstrated that mutual trust moderated the relationship between joint problem solving system and supplier relationship outcomes. Implications for theory and practice are suggested.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4331-4346
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• 2015

The femtocell network, which is designed for low power transmission and consists of consumer installed small base stations, coexists with macrocells to exploit spatial reuse gain. For its realization, cross-tier interference mitigation is an important issue. To solve this problem, we propose a joint access and power control scheme that requires limited information exchange between the femto and macro networks. Our objective is to maximize the network throughput while satisfying each user's quality of service (QoS) requirement. To accomplish this, we first introduce two distributed interference detection schemes, i.e., the femto base station and macro user equipment based schemes. Then, the proposed scheme dynamically adjusts the transmission power and makes a decision on the access mode of each femto base station. Through extensive simulations, we show that the proposed scheme outperforms earlier works in terms of the throughput and outage probability.

• Journal of Fashion Business
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• v.5 no.3
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• pp.63-71
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• 2001

The symbol of the sacred tree represents the world tree. They were influenced by Tree worship in Northern mounted nomadic groups, and the first is quite obvious, that the sacred tree is a palm tree. The Assyrian sacred tree possesses characteristics, making the tree iconographic and rather artificial. The tree typically has a thin trunk arranged in two or three tiers. Each tier is separated by horizontal plates or bands. The top of the tree is crowned with a palmette form. Wavy streamers emanate from the tree abd terminate in palmettes in a criss cross fashion. The central trunk is topped with a palmette and surrounded the trunk with palmettes emphasizing a link to date trees. The number of branches on the tree is limited, and there are usually seven, fifteen or thirty branches. The connection of these numbers with those of the week, and of the lunar wax and wane is so obvious. The branches on the tree may have indeed represented a calender of some sort. Mainly based on the excavated tomb articles of the three kingdoms and referred to Chinese and Japanese ones, Sacred Tree pattern showed that was lightly influenced by the times and area, but was slowly changed and developed to different types through those each ages generally. The Sacred Tree type was three part in according to the wavy streamers emanate from the tree abd, Sacred tree type I, Sacred tree type II, Sacred tree type III[the Mountain(; 山)-typed piled up Sacred Tree].

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.451-458
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• 2013

This paper proposes a cross-tier interference avoidance scheme to improve femtocell performance in single frequency heterogeneous cellular networks (SFHCN). The scheduled macrocell users located close femtocell base stations cause serious interference to those femtocells so that the performance of femtocell is dramatically deteriorated. To solve this problem, this paper proposes an interference avoidance scheme by reversing the uplink and downlink frames of such femtocells. After reversing the uplink and downlink frames, femtocell base station relays the macrocell user data as well as transmitting its own data. In the 1st relaying link, femtocell and macrocell users transmit their data respectively divided uplink frames and in the 2nd relaying link, femtocell base station transmit macrocell and femtocell data using a simultaneously superposition coding scheme. Computer simulation results confirm performance improvement of proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.476-483
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• 2009

Recently much attention has been devoted to femtocell's potential to improve indoor cellular coverage and high speed wireless communications. Femtocell based commercial services have been already launched in some countries and standardization activities are actively on-going, there has been concern however over potential issues of interference between femtocells and the micro/macro networks. With universal frequency reuse, the ensuing cross-tier interference causes unacceptable data rate and outage probability, so an analysis of effect of interference in femtocell embedded networks would be necessary for a stable system design. This paper investigates the effect of interference on system performances of femtocell embedded hierarchical cell structure (HCS) networks considering the characteristics of propagation environments. Various channel parameters are specially considered for indoor environments where most of femtocells are deployed to investigate the effect of interference of femtocell embedded RCS networks. System capacity and coverage are provided with variant distance between macrocell and femtocell, location of the user in femtocell coverage, and characteristic of building structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.268-276
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• 2013

In this paper, we introduce the technologies to handle the interference in the heterogeneous network and evaluate the performance of enhanced Inter-Cell Interference Coordination (enhanced ICIC, eICIC) techniques that are being introduced in 3GPP Release 10. In the time-domain eICIC scheme, time-domain resources are scheduled to avoid the interference by using Almost Blank Subframe (ABS) and Cell Range Expansion (CRE). To mitigate the cross-tier interference between macro and femtocell, it is important to efficiently combine the ABS and CRE in heterogeneous network. Since it is hard to evaluate the total throughput of heterogeneous network numerically, we evaluate the total throughput by using system level simulation (SLS). As a result of evaluation, the throughputs of many different cases of combination of ABS and CRE are compared.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1424-1432
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• 2015

As the wireless communication technologies are being studied for application to maritime communication networks in a fusion of marine industries and IT technology, interference coordination techniques have been studied in the maritime heterogeneous networks. In this paper, we develop a simulator for measuring, verifying and evaluating performance of a maritime heterogeneous network. Unlike other previous simulators, the developed simulator applies enhanced inter-cell interference coordination (eICIC) that are being introduced in the 3GPP Release 10 for mitigating the cross-tier interference between ships. Furthermore, we investigate the effects of almost blank subframes (ABS) and cell range expansion (CRE) on the throughput of small cells in maritime heterogeneous networks by using the developed simulator.