• ETRI Journal
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• v.36 no.4
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• pp.519-527
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• 2014

An integrated multi-beam satellite and multi-cell terrestrial system is an attractive means for highly efficient communication due to the fact that the two components (satellite and terrestrial) make the most of each other's resources. In this paper, a terrestrial component reuses a satellite's resources under the control of the satellite's network management system. This allows the resource allocation for the satellite and terrestrial components to be coordinated to optimize spectral efficiency and increase overall system capacity. In such a system, the satellite resources reused in the terrestrial component may bring about severe interference, which is one of the main factors affecting system capacity. Under this consideration, the objective of this paper is to achieve an optimized resource allocation in both components in such a way as to minimize any resulting inter-component interference. The objective of the proposed scheme is to mitigate this inter-component interference by optimizing the total transmission power - the result of which can lead to an increase in capacity. The simulation results in this paper illustrate that the proposed scheme affords a more energy-efficient system to be implemented, compared to a conventional power management scheme, by allocating the bandwidth uniformly regardless of the amount of interference or traffic demand.

• Journal of Communications and Networks
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• v.11 no.1
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• pp.26-35
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• 2009

In this paper, we investigate how to do resource allocation to guarantee a minimum user data rate at low signaling overhead in multi-cell orthogonal frequency division multiple access (OFDMA) wireless systems. We devise dynamic resource allocation (DRA) algorithms that can minimize the QoS violation ratio (i.e., the ratio of the number of users who fail to get the requested data rate to the total number of users in the overall network). We assume an OFDMA system that allows dynamic control of frequency reuse factor (FRF) of each sub-carrier. The proposed DRA algorithms determine the FRFs of the sub-carriers and allocate them to the users adaptively based on inter-cell interference and load distribution. In order to reduce the signaling overhead, we adopt a hierarchical resource allocation architecture which divides the resource allocation decision into the inter-cell coordinator (ICC) and the base station (BS) levels. We limit the information available at the ICC only to the load of each cell, that is, the total number of sub-carriers required for supporting the data rate requirement of all the users. We then present the DRA with limited coordination (DRA-LC) algorithm where the ICC performs load-adaptive inter-cell resource allocation with the limited information while the BS performs intra-cell resource allocation with full information about its own cell. For performance comparison, we design a centralized algorithm called DRA with full coordination (DRA-FC). Simulation results reveal that the DRA-LC algorithm can perform close to the DRA-FC algorithm at very low signaling overhead. In addition, it turns out to improve the QoS performance of the cell-boundary users, and achieve a better fairness among neighboring cells under non-uniform load distribution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.548-553
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• 2009

The aim of 4G mobile communication systems is to connect arbitrary devices to high-speed network anytime, anywhere. Cellular system must solve the problem of inter-cell interference caused by frequency reuse for meeting needs of 4G. In this paper, to solve interference problem we propose the algorithm, the so-called Threshold-Based Region Decision (TBRD) and analyze characteristics and performance of the proposed algorithm through simulation. The proposed technique has high applicability and flexibility due to simple construction using only existing UE measurement, and achieves performance improvement through the threshold that can be easily controlled.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.265-266
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• 2008

TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources. However, since the same frequency band is used in both the uplink and downlink, serious interference may occur if the base stations are not synchronized. The interference caused by different transmission directions between neighboring cells is called cross-slot interference. This paper proposes a data rate control algorithm that can decrease the cross-slot interference in TD-SCDMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.903-910
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• 2016

This paper investigates an advanced receiver for interference mitigation of downlink control channel in the 3GPP Rel-13 standard. There are several features for downlink throughput performance improvement with inter-cell interference management such as network coordination and advanced receivers during Rel-10~Rel-12. These features can be operated always under the assumption that UE perfectly decodes control channels (PCFICH and PDCCH) of serving cell. However, the performance of control channels could be deteriorated in the cell edge region due to inter-cell interference. In this paper, we introduce the advanced receivers and analyze performance for control channel interference mitigation (CCIM) based on 3GPP Rel-13 standard. Additionally, we propose UE behavior depending on network condition.

• 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.

• 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.

• 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 and Information Engineers
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• v.52 no.5
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• pp.23-32
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• 2015

The advanced receiver which can manage inter-cell interference is required to cope with the explosively increasing mobile data traffic. 3rd Generation Partnership Project (3GPP) has discussed network assisted interference cancellation and suppression (NAICS) to improve signal-to-noise-plus-interference ratio (SINR) and receiver performance by suppression or cancellation of interference signal from inter-cells. In this paper, we propose the novel hybrid receiver Full Suppression Cancellation (FSC) to reduce the interference from neighbor cell in backhaul system. The proposed receiver can suppress and cancel the interference by combining Interference Rejection Combining (IRC) with Successive Interference Cancellation (SIC). We perform the system level simulation based on 20MHz bandwidth of 3GPP LTE-Advanced system. Simulation results show that the proposed receiver can improve error rate and throughput of conventional system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.342-351
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• 2008

In this paper, a new handover procedure for OFDM-based multi-hop relay systems is proposed to reduce the handover overhead by distinguishing inter-cell handover event from intra-cell handover event at the level of physical layer using a hierarchical design concept of preamble. A Subcell ID concept for identifying RS in a cell is proposed in the design of hierarchical manner, in addition to the existing Cell ID for identifying BS. The decision on either inter-cell handover or intra-cell handover is made by the signal quality measure of CBINR(Carrier of BS to Interference and Noise Ratio) and CRINR(Carrier of RS to Interference and Noise Ratio), provided by the hierarchical preamble. The proposed handover procedure can simplify scanning procedure and skip/simplify network re-entry procedure (capability negotiation, authorization, registration), resulting in a significant reduction of handover overhead.