• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.606-609
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• 2015

Lawful Interception (LI)이란 합법적인 형태의 통신내용 및 관련 정보의 수집활동을 말한다. 최근의 4G LTE 기반의 이 기종 통신망에서의 합법적 감청은 전통적인 유선 및 3G 네트워크 중심의 감청기법 이외의 새로운 기법과 표준이 필요한 실정이다. 특히, LTE와 같이 User Equipment (UE)가 네트워크상에서 핸드오버를 통해 자유롭게 이동하거나, 3G와 같은 이 기종 망에서의 연결을 포함한 다른 사업자의 새로운 지역에서의 네트워크 연결이 보장되는 형태의 환경에서의 연속적 감청을 보장하는 것은 합법적 감청분야의 중요한 이슈중의 하나이다. 따라서, 본 논문에서는 국내의 4G-LTE망을 중심으로 기존의 3G 망을 자유롭게 이동하는 네트워크 도메인과 IMS/SIP 기반의 서버의 연속성을 보장하는 서비스 도메인 영역에서의 합법적 감청 기법을 제안한다. 본 논문에서 제안하는 기법은 이 기종 무선망과 유선망이 혼재된 네트워크에서의 IMS/SIP 기반 서비스의 이동성을 감지하여 합법적 감청의 연속성을 보장하기 위한 기법을 포함하고 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.3
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• pp.151-161
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• 2014

3GPP LTE-Advanced (Release 10) system specifies carrier aggregation (CA) to enable high data rate on using multiple frequency bands, including the variout CA-specific deployment scenarios. Considering one of those scenarios in which the different directional sector antenna is employed by each frequency band, we propose a per-carrier cell selection scheme that can improve the average throughput of the cell-edge users by allowing each user equipment (UE) to select the frequency band of the adjacent cell. Furthermore, a distributed algorithm for inter-cell copperative scheduling in this scheme is proposed to support proportional fairness among the cells. It has been shown that the proposed scheduling algorithm for the per-carrier cell selection scheme improves the cell-edge user throughput roughly by 50% over that of the conventional scheme.

• 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 Korea Institute of Information Security & Cryptology
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• v.32 no.3
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• pp.565-573
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• 2022

Current mobile communication system is in the mid-process of conversion from 4G LTE to 5G network. According to the generalization of mobile communication services, personal information such as user's identifiers and location information is transmitted through a mobile communication network. The importance of security technology is growing according to the characteristics of wireless mobile communication networks, the use of wireless shared channels is inevitable, and security technology cannot be applied to all network system elements in order to satisfy the bandwidth and speed requirements. In particular, for security threat analysis, researches are being conducted on various attack types and vulnerability analysis through rogue base stations or attacker UE to make user services impossible in the case of 5G networks. In this paper, we established a 5G network testbed using open sources. And we analyzed three security vulnerabilities related to NAS COUNT and confirmed the validity of two vulnerabilities based on the testbed or analyzing the 3GPP standard.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.11
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• pp.2015-2021
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• 2017

Recently, a lot of attention is fallen to IoT(Internet of Things) for hyper-connected society and the number of unlicensed wireless device has been increasing. Thus, this paper analyzed the impact of unlicensed wireless device on the basis of 802.11ah on licensed LTE user equipment in 900 MHz frequency band for efficient frequency use. As the interference analysis method, Minimum Coupling Loss (MCL) method and Monte Carlo (MC) method were used. In case of one interferer, minimum separation distance between interferer and victim was calculated as about 22 m through the MCL method under the assumption of the worst case. The maximum number of interferer to meet the interference probability of 5% below within a cell radius of the victim was computed as about 3000 by using MC method based on statistical technique. The analysis method and results in this paper are expected to be used for the coexistence between unlicensed wireless device and licensed wireless device.

• Journal of Communications and Networks
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• v.13 no.1
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• pp.70-76
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• 2011

This paper presents the unified user equipment (UE) baseband modulation and demodulation (modem) hardware platform architecture to support multiple radio access technologies. In particular, this platform selectively supports two systems; one is HEDGE system, which is the combination of third generation partnership project (3GPP) Release 7 high speed packet access evolution (HSPA+) and global system for mobile communication (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE), while the other is LEDGE system, which is the combination of 3GPP Release 8 long term evolution (LTE) and GSM/GPRS/EDGE. This is done by applying the flexible pin multiplexing scheme to a hardwired pin mapping process. On the other hand, to provide stable connection, high portability, and high debugging ability, the stacking structure is employed. Here, a layered board architecture grouped by functional classifications is applied instead of the conventional one flatten board. Based on this proposed configuration, we provide a framework for the verification step in wireless cellular communications. Also, modem function/scenario test and inter-operability test with various base station equipments are verified by system requirements and scenarios.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.1058-1068
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• 2017

In V2X communication, a random based resource selection scheme is needed with considerations of cases that support devices without sidelink reception capabilities and require reduction of UE's power consumption. In this paper, as improvement of D2D's resource section scheme that one TRP is repeated to data subframe pool within a PSCCH period, it is proposed that different TRPs is applied for enhanced random resource selection based on pseudo-random sequence having UE-specific seed value. By results of proposed scheme's performance by numerical analysis, it is confirmed that collision probability among resources allocated to each UE for data TB is reduced, and a number of UEs which can avoid resource collision as much as possible and have simultaneous resource allocation is increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.389-397
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• 2014

This paper focuses on advanced receiver for interference suppression or cancellation from neighbor cells in the 3GPP Rel-12 standard. From UE (User Equipment) perspective, the advanced receiver which can manage inter-cell interference of adjacent cell is required to support and manage fast-growing wireless data traffic. In 3GPP standard, NAICS which is one of approaches to improve SINR and receiver performance by directly suppression or cancellation of data (PDSCH) and control (PDCCH) signal from interference cells is discussed. In this paper, we briefly introduce the concept and candidate receivers for NAICS (Network Assisted Interference Cancellation and Suppression) based on 3GPP Rel-12 standard, and simulation results for basic NAICS receiver performance are provided.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1076-1084
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• 2012

In the CS/CB(Coordinated Scheduling/Beamforming) scheme, the cell edge user throughput is increased by selecting MIMO (Multiple Input Multiple Output) precoders which can minimize the interferences from adjacent base stations (BSs). However, in current LTE(Long Term Evolution) systems, the serving cell is selected in the initialization stage by using the synchronization signals and cell specific reference signals transmitted by adjacent BSs with a single antenna. The selected BS in the initialization stage may not be the best one since the MIMO precoding gain has not been considered in the cell selection stage. In this paper, a new cell selection technique is proposed for LTE systems with MIMO precoder by taking into account the effect of the precoder in the initialization stage. The proposed technique enables a user equipment (UE) in the cell boundary to select the serving BS by using the information (channel rank, effective channel capacity, and effective SINR(Signal to Interference plus Noise Ratio)) acquired from cell specific reference signals of candidate BSs. It is verified by computer simulation that the proposed technique can increase the channel capacity significantly in the multi-cell environments, compared with the conventional CS/CB scheme.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.13-18
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• 2016

In Long Term Evolution-Advanced (LTE-A), small cell enhancement(SCE) has been developed as a cost-effective way of supporting exponentially increasing demand of wireless data services and satisfying the user quality of service(QoS). However, there are many problems such as the transmission rate and transmission quality degradation due to the dense and irregular distribution of a large number of small cells. In this paper, we propose a clustering based interference management scheme in dense small cell network. We divide the small cells into different clusters according to the reference signal received power(RSRP) from user equipment(UE). Within a cluster, an almost blank subframe(ABS) is implemented to mitigate interference between the small cells. In addition, we apply the power control to reduce the interference between the clusters. Simulation results show that proposed scheme can improve Signal to Interference plus Noise Ratio(SINR), throughput, and spectral efficiency of small cell users. Eventually, proposed scheme can improve overall cell performance.