• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.316-323
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• 2009

Power allocation of soft frequency reuse(SFR) to increase cell edge user throughput by reducing inter-cell interference is proposed for coordinated cellular systems. SFR is the effective technique to increase cell edge user throughput, however, it costs the degradation of total system throughput. The cost increases when SFR operated in distributed resource controlled systems fails to be fast adaptive in the change of user distribution. The proposed scheme enables coordinated cells to control transmit power adaptively depending on user distribution so that it minimizes the loss of system throughput introduced from SFR while it guarantees enhancement of cell edge user throughput. Through system level simulation considering neighboring two cells, evaluation result for adaptive power allocation is shown compared with static power allocation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1125-1134
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• 2013

Small cells such as pico or femto cells are promising as a solution to cope with higher traffic explosion and the large number of users. However, the users within small cells are likely to suffer severe inter-cell interference (ICI) from neighboring base stations (BSs). To tackle this, several papers suggest BS transmit power on/off control algorithms which increase edge user throughput. However, these algorithms require centralized coordinator and have high computational complexity. This paper makes a contribution towards presenting fully distributed and low complex joint BS on/off control and user scheduling algorithm (FDA) by selecting on/off pattern of BSs. Throughput the extensive simulations, we verify the performance of our algorithm as follows: (i) Our FDA provides better throughput performance of cell edge users by 170% than the algorithm without the ICI management. (ii) Our FDA catches up with the performance of optimal algorithm by 88-96% in geometric average throughput and sufficiently small gap in edge user throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.650-669
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• 2017

Coordinated multiple points transmission and reception (CoMP) technology is used to mitigate the inter-cell interference, and increase cell average user normalized throughput and cell edge user normalized throughput. There are two kinds of radio resource schedule strategies in LTE-A/5G CoMP system, and they are called centralized scheduling strategy and distributed scheduling strategy. The regional centralized scheduling cannot solve interference of inter-region, and the distributed scheduling leads to worse efficiency in the utilize of resources. In this paper, a novel distributed scheduling scheme named 9-Cell alternate authorization (9-CAA) is proposed. In our scheme, time-domain resources are divided orthogonally by coloring theory for inter-region cooperation in 9-Cell scenario [6]. Then, we provide a formula based on 0-1 integer programming to get chromatic number in 9-CAA. Moreover, a feasible optimal chromatic number search algorithm named CNS-9CAA is proposed. In addition, this scheme is expanded to 3-Cell scenario, and name it 3-Cell alternate authorization (3-CAA). At last, simulation results indicate that 9/3-CAA scheme exceed All CU CoMP, 9/3C CU CoMP and DLC resource scheduling scheme in cell average user normalized throughput. Especially, compared with the non-CoMP scheme as a benchmark, the 9-CAA and 3-CAA have improved the edge user normalized throughput by 17.2% and 13.0% respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.9
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• pp.17-24
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• 2007

In this paper, we propose the sub-cell reuse partitioning among relays as an efficient resource reuse scheme in the relay-based OFDMA systems. If the frequency resource is reused among relays aggressively, we can increase the cell throughput. However, the interferences due to the frequency reuse may cause the fairness decrease due to the SINR degradation especially at the edge of RS sub-cells. In this paper, to make the cell throughput and fairness performance improved at the same time, we propose a sub-cell reuse partitioning scheme that divides a relay sub-cell into inner zone for aggressive reuse and outer zone for sparse reuse. The performance of the proposed scheme has been analyzed by computer simulation. We also applied a scheduling algorithm that can work together with the proposed sub-cell reuse partitioning scheme. Simulation results show that the proposed scheme can improve both the throughput and the fairness performances. In particular, when the scheduling is applied for the improvement of fairness, it is shown that the throughput performance can be enhanced more efficiently by the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.371-376
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• 2008

In this paper, we explain the unified inter-cell interference avoidance and cancellation in OFDM mobile cellular systems. Interference avoidance is used for cell-interior or two-cell-edge users, and interference cancellation is applied to three-cell-edge users. The performance of the unified scheme is evaluated by simplified system simulation. Link simulation results are used in the interpretation of system simulation output. We compare three schemes which are "no interference management," "only interference avoidance," "both avoidance and cancellation." Primary performance measures are the data rate of the 5th percentile user and the mean data rate. Simulation results show that interference management schemes greatly improve the cell edge performance, but slightly reduce the mean data rate. Use of both avoidance and cancelaltion is better than that of only avoidance in terms of the cell edge throughput and the mean data rate.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.562-570
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• 2011

In this paper, a distributed mobile relay power control (DMRPC) scheme for maximizing individual cell throughput is proposed for mobile relay aided multi-cell orthogonal frequency division multiplexing (OFDM)-time division duplex (TDD) system. In the system with DMRPC, the power levels of relay's are controlled by individual cell without cell cooperation and signalling overhead. It is demonstrated by numerical simulation that DMRPC provides the better cell throughput performance than either the full power relay aided system or conventional system without relay does. Moreover, it is also shown that relay aided systems with DMRPC, and the conventional system have almost identical cell edge throughput, while full power relay aided systems show worse performance in cell edge throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.654-659
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• 2010

In this paper, we propose a new frequency allocation method for improvement of edge and low 5% user throughputs. Although many kinds of inter cell interference mitigation methods have been proposed, those have still high complexity of implementation. The proposed algorithm has lower complexity and higher edge user throughput than conventional algorithms since the same frequency allocation method is applied in all cell. Finally, we analyze and compare the edge and low 5% user throughputs using a system level simulation (SLS).

• Journal of Life Science
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• v.18 no.9
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• pp.1312-1315
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• 2008

High throughput-drug screening plays a pivotal role for early stage of drug discovery process. In the course of assay development for screening of cell death-inducing agents, a protocol that is simple, time-saving, and high throughput-compatible was designed which was confirmed that the protocol can be worked by a HTS-compatible machine. In 96-well format, PC-3 cancer cells (1${\times}10^{4}$ cells/ml) were cultured for 24 hr. After 24 h-incubation with various medicinal plants extracts, the cells were then stained with DAPI for 30 min. The fluorescence intensity of the stained cells was measured semi-automatically with a multilabel counter. To test whether the present assay system effectively works, we screened about 850 medicinal plant extracts, and selected 1 positive crude extracts that contained cell death-inducing activity. These results suggest that the protocol is highly amenable to HTS implementation for a cell death-inducing agent(s).

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.96-102
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• 2012

The goal of mobile internet system is to provide a high-data-rate, low-latency and optimized packet radio access technology supporting flexible bandwidth deployments. Therefore, network architecture is designed with the goal to support packet-switched traffic with seamless mobility, quality of service and minimal latency. An important requirement for the mobile internet system is improved cell-edge BER performance and data throughput. This is to provide some level of service consistency in terms of geographical coverage as well as in terms of available data throughput within the communication coverage area. In a cellular system, however, the signal to interference plus noise power ratio gap between cell-center and cell-edge users can be of the order of 20 [dB]. The disparity can be even higher in a communication coverage limited cellular system. This leads to vastly lower data throughputs for the cell-edge users relative to cell-center users creating a large QoS gap. This paper proposes a analytical approach that tries to reduce inter-cell interference, and shows the SIR and BER performance according to the OFDM system parameters in mobile Internet environment.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.639-648
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• 2016

Next-generation (4G) systems are designed to support universal frequency reuse (UFR) to achieve best use of valuable spectra. However, it leads to undesirable interference level near cell borders. To control this, 4G systems adopt techniques, such as network multiple-input multiple-output (MIMO) and inter-cell interference coordination (ICIC), to improve cell-edge throughput. Network MIMO aims at mitigating inter-cell interference towards cell-edge users (CEUs) through multi-cell cooperation, where each collaborative base station serves both cell-center users (CCUs) and CEUs, including other cells' CEUs, under a power constraint. The present ICIC strategies cannot be directly applied to network MIMO because they were designed in absence of multi-cell coordination. In the presence of network MIMO, this paper investigates antenna orientations in ICIC and the method of power management. Results show that a proper antenna orientation can improve the cell-edge capacity and meantime lower the interference to CCUs. Capacity inconsistency between CCUs and CEUs is detrimental to mobile communications. Simulation results show that the proposed power management for ICIC in network MIMO systems can achieve a uniform data rate regardless users' position.