• Journal of the Korean Operations Research and Management Science Society
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• v.27 no.3
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• pp.59-74
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• 2002

This study investigates two basic operations of mobility management of PCNs (Personal Communication Networks), i.e., the location update and the paging of the mobile terminal. From the realistic consideration that a user either moves through several cells consecutively or stays in a cell with long time, we model the mobility pattern by introducing two types of CRT (Cell Residence Time). Mobility patterns of the mobile terminal are classified Into various ways by using the ratios of two types of CRT. Cost analysis is performed for distance-based and movement-based location update schemes combined with blanket polling paging and selective paging scheme. It is demonstrated that in a certain condition of mobility pattern and call arrival pattern, 2-state CRT model produces different optimal threshold and so, is more effective than IID ( Independently-Identically-Distributed) CRT model. An analytical model for the new CRT model is compact and easily extendable to the other location update schemes.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.3
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• pp.53-63
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• 2001

An efficient mobility management for mobile stations plays an important role in mobile communication network. This paper studies the mobility management scheme that combines a distance-based registration(DBR) and a selective paging (SP). We introduce an analytical model based on 2-dimensional random walk mobility model and evaluate the performance of the proposed mobility management scheme using the model to determine the optimal size of location area that results in the minimum signaling traffic on radio channels. Numerical results are provided to demonstrate the performance of the proposed mobility management scheme under various circumstances. These results can be used effectively in design and evaluation of registration methods considering the system circumstances.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.6
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• pp.90-97
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• 2012

In this paper, the new user mobility model which can be utilized to register user's location for interworking with heterogeneous overlay convergent networks under the time-varying radio propagation environment has been proposed. Thus the user mobility model is considered in order to evaluate the behaviors of users in the overlay convergent networks. This Mobile IP user mobility model will be very useful to model the user mobility behaviors and can be used to estimate the signaling traffic and frequency spectrum demands for massive data transfer for the heterogeneous overlay convergent networks.

• Korean Management Science Review
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• v.23 no.1
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• pp.21-41
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• 2006

Given the growing deployment of mobile offices, we need to understand the fectors which affect their successful use and implementation. We in this paper present a parsimonious model which integrates the IS success model and the TAM. The main feature of the model is that it allows one to explore the role of mobility of mobile office systems in determining the level of system usage and dependence. Although the mobility is the key property of any mobile system, there is little research effort exerted to understand how mobility affects the traditional IS factors such as perceived ease of use and usefulness. In addition to the system usage, this model also uses dependence as the dependent variable. This is expected to provide richer understanding of the study context. We collected survey data from 1,614 field service workers of a major domestic electronic company. They use PDAs to retrieve information regarding the specifics of the customer service requests and to report what has been done for each service job. The results from SEM analysis show that mobility improves the perceived ease of use which then leads the field service workers to depend more on the PDA systems. Interestingly enough, however, the workers' satisfaction does not cause more frequent use of the system.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.209-217
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• 2014

Of several approaches for future Internet, separating two properties of IP address into locator and identifier, is being considered as a highly likely solution. IETF's LISP (Locator ID Separation Protocol) is proposed for this architecture. In particular, the LISP model easily allows for device mobility through simple update of information at MS (Mapping Server) without a separate protocol. In recent years, some of the models supporting device mobility using such LISP attributes have emerged; however, most of them have the limitation for seamless mobility support due to the frequent MS information updates and the time required for the updates. In this paper, PMIPv6 (Proxy Mobile IPv6) model is applied for mobility support in LISP model. PMIPv6 is a method that can support mobility based on network without the help of device; thus, this we define anew the behavior of functional modules (LMA, MAG and MS) to fit this model to the LISP environment and present specifically procedures of device registration, data transfer, route optimization and handover. In addition, our approach improves the communication performance using three tunnels identified with locators between mobile node and corresponding node and using a route optimized tunnel between MN's MAG and CN's MAG. Finally, it allows for seamless mobility by designing a sophisticated handover procedure.

• Korean Journal of Biological Psychiatry
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• v.29 no.1
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• pp.1-8
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• 2022

Objectives In regard to the social competition hypothesis, depression is viewed as an involuntary defeat strategy. A previous study has demonstrated that adaptation in microenvironments can result in a wide range of behavioural patterns including defense activation disorders. Using a simulation model with evolutionary ecological agents, we explore how the fitness of various defence activation traits has changed over time in different environments with high and low social mobility. Methods The Evolutionary Ecological Model of Defence Activation Disorder, which is based on the Marginal Value Theorem, was used to examine changes in relative fitness for individuals with defensive activation disorders after adjusting for social mobility. Results Our study examined the effects of social mobility on fitness by varying the d-values, a measure of depression in the model. With a decline in social mobility, the level of fitness of individuals with high levels of defense activation decreased. We gained insight into the evolutionary influence of varying levels of social mobility on individuals' degrees of depression. In the context of a highly stratified society, the results support a mismatch hypothesis which states that high levels of defence are detrimental. Conclusions Despite the fact that niche specialization in habitats composed of multiple microenvironments can result in diverse levels of defensive activation being evolutionary strategies for stability, decreased social mobility may lead to a decrease in fitness of individuals with highly activated defence modules. There may be a reason behind the epidemic of depression in modern society.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.8
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• pp.1082-1087
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• 2021

In MANET(mobile ad hoc network), Mobility models vary according to the application-specific goals. The most widely used Random WayPoint Mobility Model(RWPMM) is advantageous because it is simple and easy to implement, but the random characteristic of nodes' movement is not enough to express the mobile characteristics of the entire sensor nodes' movements. The random mobility model is insufficient to express the inherent movement characteristics of the entire sensor nodes' movements. In the proposed Stochastic mobility model, To express the overall nodes movement characteristics of the network, the moving nodes are treated as random variables having a specific probability distribution characteristic. The proposed Stochastic mobility model is more stable and energy-efficient than the existing random mobility model applies to the routing protocol to ensure improved performances in terms of energy efficiency.

• Electrical & Electronic Materials
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• v.9 no.2
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• pp.174-179
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• 1996

We present a new physically based analytical equation for electron effective mobility in MOS inversion layers. The new semi-empirical model is accounting expicitly for surface roughness scattering and screened Coulomb scattering in addition to phonon scattering. This model shows excellent agreement with experimentally measured effective mobility data from three different published sources for a wide range of effective transverse field, channel doping and temperature. By accounting for screened Coulomb scattering due to doping impurities in the channel, our model describes very well the roll-off of effective mobility in the low field (threshold) region for a wide range of channel doping level (Na=3.0*10$^{14}$ - 2.8*10$^{18}$ cm$^{-3}$ ).

• Journal of Korean Institute of Industrial Engineers
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• v.29 no.2
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• pp.135-144
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• 2003

Traffic performance in a microcellular system is much more affected by cell dwell time and channel holding time in each cell. Cell dwell time of a call is characterized by its mobility pattern, i.e., stochastic changes of moving speed and direction. Cell dwell time provides important information for other analyses on traffic performance such as channel holding time, handover rate, and the average number of handovers per call. In the next generation mobile communication system, the cell size is expected to be much smaller than that of current one to accommodate the increase of user demand and to achieve high bandwidth utilization. As the cell size gets small, traffic performance is much more affected by variable mobility of users, especially by that of pedestrians. In previous work, analytical models are based on simple probability models. They provide sufficient accuracy in a simple second-generation cellular system. However, the role of them is becoming invalid in a picocellular environment where there are rapid change of network traffic conditions and highly random mobility of pedestrians. Unlike in previous work, we propose an improved probability model evolved from so-called Random walk model in order to mathematically formulate variable mobility of pedestrians and analyze the traffic performance. With our model, we can figure out variable characteristics of pedestrian mobility with stochastic correlation. The above-mentioned traffic performance measures are analyzed using our model.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.502-504
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• 2004

이동성이 중요시되는 네트워크에서 특정 프로토콜의 성능 평가를 위해서는 노드의 이동패턴을 정확하게 표현할 수 있는 Mobility Model이 필요하다. 노드의 연속적인 이동패턴을 필요로 하는 Mobile Ad-hoc 네트워크를 위해선 Markov process 기반의 Gauss-Markov Mobility Model이 적절하다. 그러나 맵의 엣지 부근에서 노드 이동의 부적절한 처리로 인해, 기존의 Gauss-Markov Model은 편중된 이동 패턴을 야기한다. 본 논문은 엣지 부근의 평균 이동각도를 랜덤하게 조정함으로써 기존의 모델이 가진 문제를 해결하고, 시뮬레이션을 통해서 이를 검증한다.