• International journal of advanced smart convergence
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• 제7권3호
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• pp.61-65
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• 2018

A Location Register(LR) system manages each subscriber's location information, which continuously changes in mobile cellular network. For this purpose, the LR database system provides backup management facilities. The objectives of this paper are to identify the problems of the current LR system through rigorous analysis, to suggest solutions to them. I proposed efficient backup methods that takes into account the characteristics of LR database transactions. In the proposed backup method, I use two kinds of dirty flags in order to solve the performance degradation problem caused by frequent registration- location operations.

• 한국통신학회논문지
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• 제42권4호
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• pp.750-757
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• 2017

최근 스마트폰과 모바일 단말의 수가 증가함으로서 모바일 인터넷 트래픽도 급격하게 증가하였다. D2D(Device to Device)는 급격한 인터넷 트래픽을 해결하기 위한 방법으로 주목받고 있다. D2D는 기지국이 해결해야하는 많은 트래픽 오버헤드를 줄여주고 네트워크 성능을 향상시켜준다. 그러나 D2D는 간섭이 증가하면 증가할수록 효율이 감소하는 문제를 가지고 있다. 이 논문은 업 링크 셀룰러 네트워크 환경에서 자원을 공유할 때 셀룰러의 자원효율을 높힐 수 있는 자원할당 알고리즘을 제안한다. eNB가 모든 단말의 위치를 알고 있을 때 D2D 통신은 위치 정보를 활용하여 자원할당을 한다. 제안된 기법은 D2D의 성능을 보장하기 위해 위치정보를 통하여 셀룰러 단말의 일부를 선택하게 된다. 그리고 선택된 단말만을 이용하여 자원할당을 할 단말을 찾기 시작한다. 시뮬레이션 결과에서는 D2D 성능을 최대한으로 보장하기 위해 단말 선택의 최적 값을 찾아보고 다른 자원할당기법과 비교를 해 보았다.

• 컴퓨터교육학회논문지
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• 제8권6호
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• pp.123-132
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• 2005

이동망의 위치관리에서 위치갱신 비용 최소화를 위한 많은 연구 결과들이 있다. 위치갱신 비용의 최소화를 위해서는 각 사용자들의 이동 패턴을 고려해야만 한다. 본 논문은 과거의 사용자 이동에 대한 이력으로부터 각 사용자에 대한 위치영역 리스트 생성과 이를 위한 3 단계 페이징 방안을 제안한다. 사용자의 이동은 공간적으로 뿐만 아니라 시간적으로도 규칙적인 패턴이 존재한다. 따라서 제안된 위치영역 리스트 생성방안은 이상의 2가지 측면에서 사용자의 방문빈도를 이용하여 규칙성을 발견하고, 이에 대한 위치영역리스트를 생성한다. 제안된 방안의 성능분석 위해서 제안된 방안에 대하여 사용자 이동 패턴을 고려한 모의실험을 수행하였다. 모의실험 결과 제안된 방안이 위치관리 비용 측면에서 장점이 있음이 확인되었다.

• Journal of Communications and Networks
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• 제7권2호
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• pp.207-221
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• 2005

The proliferation of wireless local area networks (WLANs) offering high data rate in hot spot area have spurred the demand for possible WLANs and third-generation (3G) cellular network integration solutions as the initiative step towards 4G systems. This paper provides a novel architecture for seamless location-aware integration of WLANs into 3G cellular networks and also an analysis for the efficient handover techniques. We introduce location as a key context in secure roaming mechanism for context-aware interworking in 4G systems. The fast secure roaming with location-aware authentication is implemented at an entity called location-aware service (LAS) broker that utilizes the concepts of direction of user and pre-warming zone. The location-ware interworking architecture supports seamless roaming services among heterogeneous wireless networks including WLANs, wireless metropolitan area networks (WMANs), and 3G cellular networks. This paper also includes a description of procedures needed to implement efficient mobility and location management. We show how the LAS broker with pre-warming and context transfer can obtain significant lower latency in the vertical handover.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권6호
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• pp.2132-2143
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• 2015

This paper presents two distance geometry-based algorithms for wireless location in cellular network systems-distance geometry filtering (DGF) and distance geometry constraint (DGC). With time-of-arrival range measurements, the DGF algorithm estimates the mobile station position by selecting a set of measurements with relatively small NLOS (non-line-of-sight) errors, and the DGC algorithm optimizes the measurements first and then estimates the position using those optimized measurements. Simulation results show that the proposed algorithms can mitigate the impact of NLOS errors and effectively improve the accuracy of wireless location.

• ETRI Journal
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• 제27권4호
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• pp.457-460
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• 2005

In this study, we consider a location-based location update (LU) scheme. We propose an enhanced LU (ELU) scheme that can store more cells to reduce the location update cost of the LU scheme and show that the ELU scheme always outperforms the LU scheme. Our scheme can be easily implemented in actual cellular systems.

• 대한임베디드공학회논문지
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• 제4권2호
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• pp.63-68
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• 2009

The location of mobile terminals in cellular networks is an important problem in the field of information technology with applications in resource allocation, location sensitive browsing, and emergency communications. Finding location estimation techniques that are robust to non-line of light (NLOS) propagation is a key problem in this area. Time of arrival (TOA) and pattern matching (PM) measurements can be made simultaneously by CDMA cellular networks at low cost. The different sources of errors for each measurement type cause TOA and PM measurements to contain independent information about mobile station (MS) locations. This paper combines the information of PM and TOA measurements to calculate a superior location estimate. The proposed location estimator is robust, provides lower error than the estimators based on the individual measurements, and has low implementation costs.

• 전자공학회논문지S
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• 제34S권3호
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• pp.1-11
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• 1997

Since the radio spectrum is limited, future wireless system will have micro cellular architecture in order to provide multimedia traffic services on personal communicatons network. The small coverage area of micro cellular systems results in frequent hadnoffs and location updates. We focuse on network load and terminal power due to frequent location updates and propose a location tracking scheme using embedded-pager PCS terminals. The proposed scheme is expected to minimize theconsumption of PCS terminal powr and improve the receiving rate of callee because of the power saving mechanism and the embedded-pager PCS terminal. This paper proposes signaling flows among the network elements for the proposed location tracking scheme. The signaling flows are accomodated to not only the existed network architectures but alsothe ATM backbone network arcitecture. To verify the signaling flows, we used petri-Net model. The resutls show that the signaling flows are suitable to our proposed location tracking scheme.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.638-648
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• 2013

Together with the GPS-based approach, geo-location through mobile communication networks is a key technology for location-based service. To save the cost, most geo-location system is implemented on the existed network service, which has a cellular structure. Still, multilateration is limited in cellular structure because it is difficult for the mobile terminal to acquire distance measurements from multiple base stations. This low hearability in the receiver is caused by co-channel interference and multipath environment. Therefore, hearability enhancement is necessary for multilateration under multipath and interference environment. Former time domain based hearability methods were designed for real signals. However, orthogonal frequency division multiplexing (OFDM) signal, which its usage has been increased in digital wireless communication, is a complex signal. Thus, different hearability enhancement method is needed for OFDM signals. This paper proposes a hearability enhancement method for forward-link multilateration using OFDM signals, which employ interference cancellation and multipath mitigation. A novel interference cancellation and multipath mitigation strategy for complex-valued OFDM signals is presented that has an iterative structure. Simulation results show that the proposed multilateration method provides the user's position with an accuracy of less than 80m through the mobile WiMAX cellular network in multipath environment.

• 산업공학
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• 제16권spc호
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• pp.21-27
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• 2003

Objective of this paper is to develop the user mobility model(UMM) which is used for the performance analysis of location update and paging algorithm and at the same time, consider the user mobility pattern(UMP) in zone-based cellular networks. User mobility pattern shows correlation in space and time. UMM should consider these correlations of UMP. K-dimensional Markov chain is presented as a UMM considering them where the states of Markov chain are defined as the current location area(LA) and the consecutive LAs visited in the path. Also, a new two dimensional Markov chain composed of current LA and time interval is presented. Simulation results show that the appropriate size of K in the former UMM is two and the latter UMM reflects the characteristic of UMP well and so is a good model for the analytic method to solve the performance of location update and paging algorithm.