• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.25-28
• /
• 1999

Consider connection-oriented wireless cellular net-works. To establish a circuit or virtual circuit in such a network, a paging message is broadcast over a region at which the destined mobile station is presumed to reside, (identified as a paging area). For an effective paging mechanism, it is desirable to provide the location information of mobile stations to the network. In this paper, we consider a mobile controlled location update scheme under which each mobile station periodically reports its current location information to the network by using an inherent timer (without measuring the power of signals transmitted from base stations). Based on the latest information about a mobile station's location, a paging area is selected to page the mobile station. Note that under this scheme, a mobile station may not yet have reported its location change while sojourning out of the current paging area. In such situation, the mobile station can not receive a paging message destined to it. Frequent location updates can reduce the paging failure rate incurred by mobile stations'sojourning out of the paging area. However, larger bandwidth is needed for location update as the location update rate is increased. On the other hand, as the size of the paging area is increased, the paging failure rate is decreased, while larger bandwidth is required for paging. Thus, we first present a model for mobility, paging and location update processes, and secondly investigate the effect of network parameters on the paging failure rate and the amount of bandwidth used for paging and location update. Finally, we formulate problems to find proper values for the location update rate and paging area size under the constraints on the bandwidth usage levels for location update and paging.

• International Journal of Internet, Broadcasting and Communication
• /
• 제12권2호
• /
• pp.144-149
• /
• 2020

A database called Home Location Register(HLR) plays a major role in location management in mobile cellular networks. The objectives of this paper are to identify the problems of the current HLR system through rigorous analysis, to suggest solutions to them. The current HLR backup method is a process of simply writing the changed memory SLD block to disk, which has a problem in maintaining database consistency. Since information change and backup are performed separately by separate processes, there is a risk of information inconsistency when an error restart occurs. To solve this problem, a transaction concept was introduced for subscriber-related operation functions and a recovery method through logging and checkpointing was introduced. The subscriber related functions of tasks terminated normally by the suggested process are recovered with consistency even after system restarts. Performance is also not affected seriously because disk tasks for log occur with only subscriber related functions.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.114.4-114
• /
• 2001

Recently, variety services are more and more developed due to supply of PDA, cellular phone, and etc. Also, a services based on location information are very helpful in traffic, shopping, and emergency. Thus the user position is positively necessary for these services. One of the latest applications in GPS is the E911 call service for wireless phones. In this case, current GPS Navigation accuracy meets the FCC requirements but the hardware size and power consumption of GPS is issued for implementation. And, some case of applications need to snapshot location solution with fast TTFF(Time-To-Fist-Fix) than continuous location solution. The software GPS receiver could be the solution ...

• 산업기술연구
• /
• 제27권A호
• /
• pp.141-147
• /
• 2007

In this paper, we define the multi-states exponential cell resident time mobility model for describing the mobility characteristics of mobile user and analyzed the total cost of the hybrid method using multi-states cell resident time. Generally, the mobile user has three states for its movement, such as staying, walking and driving. This multi-states cell resident time based hybrid method reflects the movement characteristics of mobile user and adapts the location update period according to the states of mobility speed. As a results of the performance analysis, we can get the optimum parameters of the hybrid method for multi-states based mobile users.

• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2005년도 하계학술대회
• /
• pp.318-322
• /
• 2005

An IP address plays both endpoint identifier and location identifier in wire based network. However, one IP address can not provide both endpoint identifier and location identifier for mobile Internet environment such as cellular network and portable Internet. To resolve this problem, mobile IPv4 and mobile IPv6 technologies are developed. These technologies are based on the concept of separation the endpoint identifier from location identifier. This paper describes some results of the recent studies such as mobile IPv4, mobile IPv6, host identify protocol and so on. Also, we propose the criteria to decide which technologies are suitable for deployment in the practical network environment.

• International journal of advanced smart convergence
• /
• 제8권2호
• /
• pp.39-46
• /
• 2019

Human mobility estimation plays a key factor in a lot of promising applications including location-based recommendation systems, urban planning, and disease outbreak control. We study the human mobility estimation problem in the case where recent locations of a person-of-interest are unknown. Since matrix decomposition is used to perform latent semantic analysis of multi-dimensional data, we propose a human location estimation algorithm based on matrix factorization to reconstruct the human movement patterns through the use of information of persons with correlated movements. Specifically, the optimization problem which minimizes the difference between the reconstructed and actual movement data is first formulated. Then, the gradient descent algorithm is applied to adjust parameters which contribute to reconstructed mobility data. The experiment results show that the proposed framework can be used for the prediction of human location and achieves higher predictive accuracy than a baseline model.

• IEIE Transactions on Smart Processing and Computing
• /
• 제1권2호
• /
• pp.117-124
• /
• 2012

A client collaboration (CC) system is proposed for a user relay system. The proposed scheme focuses on the management of transmit power and leakage interference. In the proposed CC system, edge users transmit signals to the masters considered as user relays. The masters relay the signals of the edge users to the base station using the resource blocks (RBs) that are assigned to the edge users. The leakage interference and power consumption were analyzed in the CC system. In addition, an optimal master location problem was formulated based on the signal-to-leakage-plus-noise ratio (SLNR). Because the optimal master location problem is quite complex, a sub-optimal master location problem was proposed and a closed-form sub-optimal master location was obtained. The edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC. The numerical results showed that the edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC, and the average throughput increases.

• 한국컴퓨터산업학회논문지
• /
• 제4권12호
• /
• pp.986-998
• /
• 2003

이동 객체 관리 시스템은 사람, 동물, 자동차, 휴대용 단말기 등과 같이 시간에 따라 연속적으로 위치를 변경하는 시공간 데이터를 관리하며, 차량 추적 시스템, 디지털 전장, 동물 서식지 관리등과 같은 위치기반서비스에 적용된다. 기존의 이동 객체 관리 시스템은 이동 객체의 불확실한 위치 추정 기능을 제공하지 못하며, 실시간 환경에서 발생되는 위치 정보의 손실을 처리하지 못한다 이로 인해 사용자가 요청하는 질의에 응답하지 못하거나 부정확한 질의 처리 결과를 제공하는 문제점이 발생된다. 이 논문에서는 이와 같은 문제점을 해결할 수 있는 이동 객체 관리 시스템을 설계한다. 제안 시스템은 시간에 종속적인 위치 변화 함수를 이용하여 이동 객체의 과거 및 미래의 위치 정보를 함께 처리할 수 있다. 또한, 실시간 환경에서 발생되는 이동 객체의 위치 정보 손실을 보완하기 위한 위치 정보 트리거링 기법을 제안한다. 마지막으로, 제안 시스템을 PDA 기반의 차량 검색 시스템에 적용 및 구현한다 이로 인해 제안 시스템이 위치기반서비스에 적용 가능함을 보인다.

• 대한전자공학회논문지TC
• /
• 제47권1호
• /
• pp.35-42
• /
• 2010

이동 통신망을 이용한 지상파 측위 기술은 GPS와 더불어 LBS를 구성하기 위한 핵심 기술이다. WiBro 시스템은 차세대 통신망으로 주목 받고 있으며, WiBro 망에서 매 프레임마다 방송되는 프리앰블 심볼의 특성을 이용하면 TDOA 방식의 무선 측위가 가능하다. 그러나 WiBro 시스템은 셀룰러 구조로 되어 있기 때문에 일반적으로 단말기가 다수의 기지국 신호로부터 거리정보를 구하기 어렵다. WiBro 망에서 삼변측량을 이용한 무선 측위를 하기 위해서는 수신 신호의 세기를 증가시켜야 하며, 장기 중첩 기법을 이용하여 가청성을 향상 시킬 수 있다. 본 논문에서는 주파수 잔여 오차와 수신 신호의 SNR에 따른 동기 중첩 및 비동기 중첩의 성능을 비교하여 WiBro 망에서 최적의 혼합 중첩 방법을 제시하였다. 컴퓨터 시뮬레이션을 통하여 혼합 중첩의 성능을 분석하고 WiBro 망을 이용한 무선 측위의 가능성 및 한계를 확인하였다.

• 한국통신학회논문지
• /
• 제35권12B호
• /
• pp.1199-1210
• /
• 2010

최근 Ad-hoc 통신과 관련하여 기회 컴퓨팅(Opportunistic Computing)에 대한 관심이 점차로 커지고 있으며 실질적인 서비스 및 관련된 요구사항에 대한 연구가 크게 요구되고 있다. 본 논문에서는 가상의 기회 컴퓨팅 응용서비스인 "어린이 보호 시스템"에 대해 먼저 논의하고 이 서비스에 적합하도록 새롭게 제작된 사용자용 Ad-hoc 통신 장치인 휴대폰 연동형 노드(uMobile)와 의복내장형 노드(uClo)를 제안한다. uMobile은 휴대폰에 연결되어 휴대폰 통신과 Ad-hoc 통신을 연동할 수 있고 uClo는 다양한 센서를 사용하여 사용자의 상태정보를 인식하며 의복에 내장될 수 있도록 제작되었다. 개발된 통신 장치를 사용하여 위치인식과 상황인지 서비스를 구현하였고 실제 실내 환경에서 테스트하여 그 결과를 나타내었다. 본 연구가 기회 컴퓨팅 기반의 다양한 서비스를 위한 참조 서비스로 활용될 수 있을 것으로 기대한다.