• Information and Communications Magazine
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• v.28 no.8
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• pp.10-17
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• 2011

3GPP($3^{rd}$ Generation Partnership project)는 3세대 이동통신인 UMTS(Universal Mobile Telecommunication System)의 초기 표준화 이후 HSPA(High Speed Packet Access), MBMS(Multimedia Broadcast Multicast Service) 등의 기술 개발로 UMTS시스템을 지속적으로 발전시켜 왔다. 그리고, 최근 새로운 무선 접속 기술을 기반한 LTE(Long Term Evolution)시스템에 대한 표준화를 완료하고 ITU-T(International Telecommnunications Union-Radio)의 IMT-Advanced 요구사항을 만족하는 LTE-Advanced 시스템에 대한 연구를 진행하고 있다. 한편 LTE-Advanced 표준의 목표인 무선 전송속도를 한층 더 높이고, 단위비용(cost per bit)을 더욱 낮추고, 셀 커버리지 및 용량을 확대하기 한 저출력의 피코셀, 펨토셀, 무선중계기들을 이용하여 실내외의 소규모 영역을 서비스하도록 하는 heterogeneous network에 대한 국제 표준이 활발히 논의되고 있다. 그러나 여러 셀이 혼재하는 경우 셀들간의 신호 간섭이 발생하여 사용자의 통신 품질이 크게 저하될 우려가 있다. 본 고에서는 heterogeneous network 와 관련하여 국제 표준 LTE-Advanced에서 논의되고 있는 간섭 제어 기법에 대해 소개한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.69-70
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• 2013

Through shipbuilding industry and IT convergence, high effiency of production facilities and process will be achieved. Using LTE based communicator, variable sensing data obtained from shipyard cabe be transmitted to central server. This agent system can be applied to total monitoring, sail test, and accident prevention, etc.

• Journal of Information Processing Systems
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• v.4 no.4
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• pp.145-152
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• 2008

The specification of the Home Evolved NodeB (Home-eNB), which is a small base station designed for use in residential or small business environment, is currently ongoing in 3GPP LTE (Long Term Evolution) systems. One of the key requirements for its feasibility in the LTE system is the mobility management in the deployment of the numerous Home-eNBs and other 3GPP network. In this paper, we overview the characteristic of Home-eNB and also describe the mobility management issues and the related approaches in 3GPP LTE based Home-eNB systems.

• Journal of Auto-vehicle Safety Association
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• v.15 no.4
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• pp.65-70
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• 2023

In the paper, we propose a design method and process of a hybrid V2X communication module that combines WAVE communication, LTE-V2X communication, and legacy LTE communication in evaluating vehicle V2X electromagnetic compatibility. C-ITS is suitable for safety service applications due to its low latency, and legacy LTE is suitable for applications such as traffic information and infotainment due to its high latency and high capacity. In order to evaluate the V2X communication system, the evaluation equipment must have communication performance of the same level or higher. The main design contents presented in this paper will be applied to the implementation of a hybrid V2X communication module for electromagnetic compatibility evaluation.

• Journal of KIISE
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• v.41 no.9
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• pp.715-727
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• 2014

The number of subscribers in 4th generation mobile system has been increased rapidly. Along with that, preserving subscribers' privacy has become a hot issue. To prevent users' location from being revealed publicly is important more than ever. In this paper, we first show that the privacy-related problem exists in user authentication procedure in 4th generation mobile system, especially LTE. Then, we suggest an attack model which allows an adversary to trace a user, i.e. he has an ability to determine whether the user is in his observation area. Such collecting subscribers' location by an unauthorized third party may yield severe privacy problem. To keep users' privacy intact, we propose a modified authentication protocol in LTE. Our scheme has low computational overhead and strong secrecy so that both the security and efficiency are achieved. Finally, we prove that our scheme is secure by using the automatic verification tool ProVerif.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3A
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• pp.217-224
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• 2010

In this paper, we propose a hard handover algorithm for a base station's self-optimization, one of the automatic operational technologies for the 3GPP LTE systems. The proposed algorithm simultaneously considers a mixed target sell selection method for optimal selection and a multiple parameter based active hysteresis method with the received signal strength from adjacent cells and the cell load information of the candidate target cells from information exchanges between eNBs through X2 interface. The active hysteresis method chooses optimal handover hysteresis value considering the costs of the various environmental parameters effect to handover performance. The algorithm works on the optimal target cell and the hysteresis value selections for a base station's automatic operational optimization of the LTE system with the gathered informaton effects to the handover performance. The simulation results show distinguished handover performances in terms of the most important performance indexes of handover, handover failure rate and load balancing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9A
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• pp.656-663
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• 2009

In 3GPP LTE system downlink, PSS (primary synchronization signal) and SSS (secondary synchronization signal) sequences are used for initial cell search and synchronization. UE (user equipment) detects slot timing, frequency offset, and cell ID by using PSS. After that it should detect frame timing, cell group ID, and CP length by using SSS. But in 3GPP LTE, there are two kinds of CP length, so we should operate FFT twice. In this paper, to minimize SSS detection complexity in cell searcher, we propose a CP length pre-decision algorithm that reduces the arithmetical complexity by half at most, with negligible performance degradation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.498-508
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• 2009

In wireless mobile environments, large bandwidth and high QoS (Quality of Service) are recently required to support the increased demands for multimedia services. LTE (Long Term Evolution) is one of the promising solutions for the next generation broadband wireless access systems. To efficiently use downlink resource and effectively support QoS, packet scheduling algorithm is one of the important features in LTE system. In this paper, we proposed DAPS (Delay-Aware Packet Scheduling) algorithm to consider QoS requirements of delays for various traffic classes as well as channel condition and fairness. To reflect delay experiences at scheduling instance, DAPS observes how queue waiting time of packet is closed to maximum allowable delay. The simulation results show that the DAPS algorithm yields better performance for delay experience by increasing the number of transmitted packets with satisfying the required delay time compared with existing scheduling algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.565-572
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• 2007

3G Long Term Evolution (3G LTE) is a next generation cellular networks system capable or providing various mobile multimedia services by using OFDMA and MIMO based radio access technology. Among many differences from existing WCDMA based systems, the facts that 3G LTE uses Physical Resource Block (PRB) as its radio resources and provides all services through the PS domain make the development of new resource management schemes necessary. This paper proposes an adaptive partitioning based downlink call admission control scheme. It separates realtime call requests from non-realtime ones, specifies maximum allowable resource amounts for each type, but if the maximum is exceeded, call requests are accepted with probability proportional to remaining resource amounts. Despite the fact that such adaptive concept has been already adopted by other call admission schemes, the contributions of our paper, which are that we are able to find an efficient way to apply the proposed scheme exploiting PRB characteristics and measure the resource usage of base stations by PRB utilization and payload ratio, are still valid. When judging from simulation results in comparison with others, our scheme is able to prioritize realtime call requests over non-realtime ones, and at the same time, overall system performance is superior.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.5
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• pp.356-364
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• 2019

The Ministry of Science and ICT recently announced its policy direction that involves charging the economic value of radio spectrum for promoting its efficient usage. According to the policy, there will be much efforts to estimate the economic values of various usages of radio spectrum. In this study, the economic value of radio spectrum is estimated for trunked radio system(TRS) by employing the least cost alternative methodology. The proposed methodology estimates the value of radio spectrum according to the cost of an alternative that can be employed for providing the same service. The value of radio spectrum for TRS was determined on the basis of the cost associated with the provision of TRS through the LTE network, wherein the value of radio spectrum for TRS comprises the LTE network cost, capital expenditure for the LTE service, subsidy for the LTE handset, and compensation cost for migration. Results obtained from this study can aid in calculating the economic values of radio spectra for other services and applications.