• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권8호
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• pp.3068-3078
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• 2015

Although the massive MIMO system supports a high throughput, it requires a lot of channel information for channel compensation. For the reduction of overhead, the massive MIMO system generally uses TDD as duplexing scheme. Therefore, the massive MIMO system is sensitive to rapidly changing fast fading in according to time. For the improvement of reduced SINR by fast fading, the adaptive power control is proposed. Unlike the conventional scheme, the proposed scheme considers mobility of device for adaptive power control. The simulation of the proposed scheme is performed with consideration for mobility of device. The result of the simulation shows that the proposed scheme improves SINR. Since SINR is decreased in according to the number of device in the network by unit of cell, each base station can accommodate more devices by the proposed scheme. Also, because the massive MIMO system with high SINR can use high order modulation scheme, it can support higher throughput.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.498-501
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• 2009

Electrophoretic displays (EPDs) are attracting considerable attentions as a paper-like display. Especially, Electrophoretic cell consists of micron-sized, charged particles dispersed in a viscous fluid. When an external electric field is applied, the charged particles move with a speed proportional to the particle mobility and the local field strength. In electrophoretic displays fast switching times are required, so knowing the particle mobility is very important. In this paper, we study a novel simulation for calculating the particle motions submerged in a viscous fluid for horizontal switching electrophoretic cell.

• 한국통신학회논문지
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• 제28권1B호
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• pp.64-70
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• 2003

In order to provide seamless wireless Internet service, the basic mobile IP protocol should be enhanced to solve packet loss problem from large registration latency because frequent handoffs occur in cellular networks. In this paper, we suggest a new micro-mobility management protocol based on MPLS while supporting Qos, and evaluate its performance using simulation. We use MPLS label switching techniuqe in cellular access networks to simplify location management and speed up packet transmission. We adopt context transfer procedure to minimize the delay needed to attain prior level of service after handoff Packet loss can be minimized during handoff by transmitting received packets from old BSLER to new BSLER using a spliced LSP between them. Simulation results show that the proposed MPLS-based micro-mobility management protocol provides a seamless handoff and supports QoS of user traffic.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.3018-3040
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• 2018

The mobility model is one of the most important factors that impacts the evaluation of any transportation vehicular networking protocols via simulations. However, to obtain a realistic mobility model in the dynamic urban environment is a very challenging task. Several studies extract mobility models from large-scale real data sets (mostly taxi GPS data) in recent years, but they do not consider the statuses of taxi, which is an important factor affected taxi's mobility. In this paper, we discover three simple observations related to the taxi statuses via mining of real taxi trajectories: (1) the behavior of taxi will be influenced by the statuses, (2) the macroscopic movement is related with different geographic features in corresponding status, and (3) the taxi load/drop events are varied with time period. Based on these three observations, a novel taxi mobility model (T-START) is proposed with respect to taxi statuses, geographic region and time period. The simulation results illustrate that proposed mobility model has a good approximation with reality in trajectory samples and distribution of nodes in four typical time periods.

• 한국정보과학회논문지:정보통신
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• 제29권3호
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• pp.216-223
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• 2002

본 논문에서는 차세대 셀룰라 이동통신망을 위한 효율적인 위치관리기법을 설계한다 제안된 기법에서는 사용자를 이동성 특성에 따라 HMU(high mobility user)와 LMU(low mobility user) 두 가지 클래스(class)로 분류하고, 각 사용자 클래스에 따라 각각 적합한 서로 다른 기법으로 위치를 관리한다. 제안된 기법과 순수 지능 페이징 기법의 성능을 컴퓨터 시뮬레이션을 이용하여 비교하여, 제안된 기법이 순수한 지능 페이징 기법에 비해 우수한 성능을 제공함을 보인다.

• 한국정보과학회논문지:정보통신
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• 제33권1호
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• pp.28-37
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• 2006

최근 새로운 트랜스포트 계층 프로토콜인 SCTP를 기반으로 한 트랜스포트 계층 이동성 지원방안이 제안되었다. 본 논문에서는 이들 트랜스포트 계층 이동성 지원 방안이 지금까지 제안되어 온 대표적인 IPv6 기반 네트워크 계층에서의 이동성 지원 방안들에 비하여 어느 정도의 성능을 보이는지 그 위치를 가늠해 보고, 이들 각 프로토콜이 수반하는 오버헤드를 비교하였다 시뮬레이션 결과를 통하여 트랜스포트 계층에서의 종단 간 이동성 지원 방안이 네트워크 계층 이동성 지원 방안들이 수반하는 오버헤드보다 더 낮은 오버헤드를 가지며 전송 성능이나 핸드오버 지연 측면에서 MIPv6와 유사하거나 더 좋은 성능을 보임을 알 수 있었다.

• ETRI Journal
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• 제28권6호
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• pp.799-802
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• 2006

Capacity has always been a major concern in wireless networks. This letter studies the impact of mobility on the overall system capacity in wireless cellular networks. In this letter, we present a simple system model which we developed to capture the inherent relationships among system capacity, new call blocking probability, handoff dropping probability, call terminating probability, and bandwidth utilization rate. We investigate the complex relationship between mobility and capacity-related parameters. Through simulation, we demonstrate that mobility has a significant impact on capacity and is reversely proportional to the bandwidth reserved for handoff traffic.

• Journal of Communications and Networks
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• 제11권4호
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• pp.337-349
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• 2009

In this paper, we introduce a novel mobility model for mobile sinks in which the sinks move towards randomly distributed destinations, where each destination is associated with a mission. The novel mobility model is termed the random mobility with destinations. There have been many studies on mobile sinks; however, they merely support two extreme cases of sink mobility. The first case features the most common and general mobility, with the sinks moving randomly, unpredictably, and inartificially. The other case takes into account mobility only along predefined or determined paths such that the sinks can gather data from sensor nodes with minimum overhead. Unfortunately, these studies for the common mobility and predefined path mobility might not suit for supporting the random mobility with destinations. In order to support random mobility with destination, we propose a new protocol, in which the source nodes send their data to the next movement path of a mobile sink. To implement the proposed protocol, we first present a mechanism for predicting the next movement path of a mobile sink based on its previous movement path. With the information about predicted movement path included in a query packet, we further present a mechanism that source nodes send energy-efficiently their data along the next movement path before arriving of the mobile sink. Last, we present mechanisms for compensating the difference between the predicted movement path and the real movement path and for relaying the delayed data after arriving of the mobile sink on the next movement path, respectively. Simulation results show that the proposed protocol achieves better performance than the existing protocols.

• Journal of Information Processing Systems
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• 제13권2호
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• pp.236-255
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• 2017

The rapid growth of smart devices demands an enhanced throughput for network connection sustainability during mobility. However, traditional wireless network architecture suffers from mobility management issues. In order to resolve the traditional mobility management issues, we propose a novel architecture for future wireless access network based on software-defined network (SDN) by using the advantage of network function virtualization (NFV). In this paper, network selection approach (NSA) has been introduced for mobility management that comprises of acquiring the information of the underlying networking devices through the OpenFlow controller, percepts the current network behavior and later the selection of an appropriate action or network. Furthermore, mobility-related scenarios and use cases to analyze the implementation aspects of the proposed architecture are provided. The simulation results confirm that the proposed scenarios have obtained a seamless mobility with enhanced throughput at minimum packet loss as compared to the existing IEEE 802.11 wireless network.

• Journal of Computing Science and Engineering
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• 제9권3호
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• pp.155-162
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• 2015

The last decade has seen a rapid growth in the use of mobile devices all over the world. With an increasing use of mobile devices, mobile applications are becoming more diverse and complex, demanding more computational resources. However, mobile devices are typically resource-limited (i.e., a slower-speed CPU, a smaller memory) due to a variety of reasons. Mobile users will be capable of running applications with heavy computation if they can offload some of their computations to other places, such as a desktop or server machines. However, mobile users are typically subject to dynamically changing network environments, particularly, due to user mobility. This makes it hard to choose good offloading decisions in mobile environments. In general, users' mobility can provide some hints for upcoming changes to network environments. Motivated by this, we propose a mobility model of each individual user taking advantage of the regularity of his/her mobility pattern, and develop an offloading decision-making technique based on the mobility model. We evaluate our technique through trace-based simulation with real log data traces from 14 Android users. Our evaluation results show that the proposed technique can help boost the performance of mobile devices in terms of response time and energy consumption, when users are highly mobile.