Showing papers on "Mobility model published in 2000"

Empirical low-field mobility model for III-V compounds applicable in device simulation codes

Abstract: A Caughey–Thomas-like mobility model with temperature and composition dependent coefficients is used in this work to describe the dependence of electron and hole mobilities on temperature, doping concentration, and alloy composition. Appropriate parameter sets are given for a large number of III–V binary and ternary compounds, including: GaAs, InP, InAs, AlAs, GaP, Al0.3Ga0.7As, In0.52Al0.48As, In0.53Ga0.47As, and In0.49Ga0.51P. Additionally, physically justifiable interpolation schemes are suggested to find the mobilities of various ternary and quaternary compounds (such as AlxGa1−xAs, In1−xGaxP, In1−xGaxAs, In1−xAlxAs, and In1−xGaxAsyP1−y) in the entire range of composition. The models are compared with numerous measured Hall data in the literature and very good agreement is observed. The limitations of the present model are also discussed. The results of this work should be extremely useful in device simulation packages, which are currently lacking a reliable mobility model for the above materials.

Mobility prediction in wireless networks

Abstract: Wireless networks allow a more flexible communication model than traditional networks since the user is not limited to a fixed physical location. Unlike cellular wireless networks, ad hoc wireless networks do not have any fixed communication infrastructure. In ad hoc networks, routes are mostly multihop and network hosts communicate via packet radios. Each host moves in an arbitrary manner and thus routes are subject to frequent disconnections. In typical mobile networks, nodes exhibit some degree of regularity in the mobility pattern. By exploiting a mobile user's non-random traveling pattern, we can predict the future state of network topology and thus provide a transparent network access during the period of topology changes. In this paper we present various enhancements to unicast and multicast routing protocols using mobility prediction. The proposed scheme utilizes GPS location information. By simulation, we evaluate the effectiveness of mobility prediction.

Using semantic caching to manage location dependent data in mobile computing

Abstract: Location-dependent applications are becoming very popular in mobile environments. To improve system performance and facilitate disconnection, caching is crucial to such applications. In this paper, a semantic caching scheme is used to access location dependent data in mobile computing. We first develop a mobility model to represent the moving behaviors of mobile users and formally define location dependent queries. We then investigate query processing and cache management strategies. The performance of the semantic caching scheme and its replacement strategy FAR is evaluated through a simulation study. Our results show that semantic caching is more flexible and effective for use in LDD applications than page caching, whose performance is quite sensitive to the database physical organization. We also notice that the semantic cache replacement strategy FAR, which utilizes the semantic locality in terms of locations, performs robustly under different kinds of workloads.

TeleMIP: telecommunications-enhanced mobile IP architecture for fast intradomain mobility

Abstract: This article first surveys existing protocols for supporting IP mobility and then proposes an extension to the mobile IP architecture, called TeleMIP. Our architecture attempts to achieve smaller handoff latency by localizing the scope of most location update messages within an administrative domain or a geographical region. TeleMIP is intended for use in evolving third-generation wireless networks, and introduces a new logical entity, called the mobility agent, which provides a mobile node with a stable point of attachment in a foreign network. While the MA is functionally similar to conventional foreign agents, it is located at a higher level in the network hierarchy than the subnet-specific FAs. Location updates for intradomain mobility are localized only up to the MA; transmission of global location updates are necessary only when the mobile changes administrative domains and/or geographical regions. By permitting the use of private or locally scoped addresses for handling intradomain mobility, TeleMIP allows efficient use of public address space. Also, by reducing the frequency of global update messages, our architecture overcomes several drawbacks of existing protocols, such as large latencies in location updates, higher likelihood of loss of binding update messages, and loss of inflight packets, and thus provides better mobility support for real-time services and applications. The dynamic creation of mobility agents (in TeleMLP) permits the use of load balancing schemes for the efficient management of network resources.

HMIPv6: A hierarchical mobile IPv6 proposal

Abstract: The IETF Mobile IPv6 protocol has been developped to manage global (macro) mobility. It is not adapted to local (micro) mobility since it does not support any kind of hierarchy. This paper presents a hierarchical protocol, built on top of Mobile IPv6, that separates local mobility (within a site) from global mobility (across sites) management. Local handoffs are managed locally and transparently to a mobile node' correspondent hosts while global mobility is managed with Mobile IPv6. Our scheme is flexible (several levels of hierarchy can be used), scalable, interworks with Mobile IPv6 and can be deployed gradually.

Method and apparatus for providing mobility within a network

Abstract: The present invention is a novel method and apparatus for providing transparent mobility of an entity within a network. The present invention allows a given entity, which has a communication path set up between it and a peer entity, to move from one location to another, without informing the peer entity of this movement, and without having the communication path broken. The present invention is applicable to decentralized networks using the IP protocol, and is particularly applicable on networks wherein it is desired that the mobility mechanism neither introduces latency nor decreases the available bandwidth of the network. In the present invention, neither is latency increased nor is bandwidth utilization increased, as is done in other mobility models. Additionally, the present invention utilizes standard protocols that are widely available from a plurality of equipment manufacturers on a variety of platforms. Thus, the present invention provides a very cost-effective model for network providers that need to support transparent mobility within their network.

Seven degrees of separation in mobile ad hoc networks

Abstract: We present an architecture that enables the sharing of information among mobile, wireless, collaborating hosts that are intermittently connected to the Internet. Participants in the system obtain data objects from Internet-connected servers, cache them and exchange them with others who are interested in them. The system exploits the fact that there is a high locality of information access within a geographic area. It aims to increase the data availability to participants with lost connectivity to the Internet. We investigate how user mobility and query patterns affect data dissemination in such an environment. We discuss the main components of the system and possible applications. Finally, we present simulation results that show that the ad hoc networks can be very effective in distributing popular information.

Nonclassical traffic modeling and performance analysis of cellular mobile networks with and without channel reservation

Abstract: We present a two-moment performance analysis of cellular mobile networks with and without channel reservation. Unlike classical analysis where handoff traffic is modeled as Poisson, we characterize handoff traffic as a general traffic process and represent it using the first two moments of its offered traffic. We empirically show that handoff traffic is a smooth process under negative exponential channel holding times. We also show how one may determine customer-oriented grade-of-service parameters such as new-call blocking, handoff call blocking, and forced termination probability under the two-moment representation of traffic offered to each cell. We present extensive results validating our analysis. We compare the performance of the proposed two-moment analysis with classical single-moment analysis and simulation results. Our simulation employs five different mobility models. We show that our proposed model outperforms the existing analytical method when compared to simulation results employing all five mobility models.

Paging area optimization based on interval estimation in wireless personal communication networks

Abstract: We consider an optimum personal paging area configuration problem to improve the paging efficiency in PCS/cellular mobile networks. The approach is to set up the boundaries of a one-step paging area that contain the locations of a mobile user with a high probability and to adjust the boundaries to gain a coverage that is matched to the mobile user's time-varying mobility pattern. We formulate the problem as an interval estimation problem. The objective is to reduce the paging signaling cost by minimizing the size of the paging area constrained to certain confidence measure (probability of locating the user), based on a finite number of available location observations of the mobile user. Modeling user mobility as a Brownian motion with the drift stochastic process and by estimating the parameters of the location probability distribution of the mobility process, the effects of the mobility characteristics and the system design parameters on the optimum paging area are investigated. Results show: (1) the optimum paging area expands with the time elapsed after the last known location of the user; (2) it also increases with the length of a prediction interval and the location probability; (3) the relative change in the paging area size decreases with the increase in the number of location observations.

Context-Aware Shared Control of a Robot Mobility Aid for the Elderly Blind

Abstract: This paper describes the use of a Bayesian network to provide context-aware shared control of a robot mobility aid for the frail blind. The robot mobility aid, PAM-AID, is a “smart walker” that aims to assist the frail and elderly blind to walk safely indoors. The Bayesian network combines user input with high-level information derived from the sensors to provide a context-aware estimate of the user’s current navigation goals. This context-aware action selection mechanism facilitates the use of a very simple, low bandwidth user interface, which is critical for the elderly user group. The PAM-AID systems have been evaluated through a series of field trails involving over 30 potential users.

Characterization of user mobility in low earth orbit mobile satellite systems

Abstract: Future mobile communication networks will provide a global coverage by means of constellations with nongeosynchronous satellites. Multidspotdbeam antennas on satellites will allow a cellular coverage all over the Earth. Due to the unstationarity of satellites a call may require many cell changes during its lifetime. These passages will be managed by interdbeam handover procedures. This paper deals with the modeling of the user cell change process during call lifetime in Low Earth OrbitdMobile Satellite Systems lLEOdMSSsr. The analytical derivations presented in this study can be also applied to different mobility models provided that basic assumptions are fulfilled. This paper evaluates the impact of user mobility on the blocking performance of channel allocation techniques. Moreover, the handover arrival process towards a cell has been characterized by using a usual statistical parameter for stationary point processes. Finally, a performance analysis has been carried out on the basis of the classic teletraffic theory for telephone systems.

A mobile agent infrastructure for terminal, user, and resource mobility

Abstract: The telecommunication and the Internet scenarios have pointed out the possibility of accessing resources and services while moving in open distributed global systems. Mobility should allow users to access services and to maintain their preferred working environment independently of their current point of attachment, and has motivated the investigation of new models and solutions. The mobile agent technology is intrinsically suitable to describe, model and implement mobility. The paper describes how a mobile agent framework, called SOMA, can provide an infrastructure to support not only the traditional concepts of terminal and user mobility but also the mobility of resources in general. SOMA permits terminal mobility by introducing the mobile place abstraction that represents a mobile host for agent execution, and user mobility by supporting the virtual home environment service. SOMA supports resource mobility via the resource discovery service that can preserve client/server relationships among SOMA resources and users independently of current positions. The paper also gives experimental results about the costs associated with the main mechanisms for supporting terminal, user, and resource mobility.

H.323 mobility protocol for terminal, user and service mobility

Abstract: The H.323 standard is extended to support mobility in a multimedia communication system with services over packet-based networks. Such mobility is supported in a transport independent way. New H.323 messages and/or message elements have been created, and extensions to existing messages provided to accommodate mobility. Messages are provided to facilitate mobility binding as the mobile entity moves from one place to another. The mobile entity periodically registers with different gatekeepers to obtain support for an H.323 communication that includes at least one of audio, video and data.

Selection of mobility agent in access network

Abstract: In an access network which supports macro mobility management, an access node (SGSN) checks (3) during an attach procedure of a mobile station (MS) whether the mobile has macro mobility capability, i.e. whether there is a potential need for macro mobility services. Macro mobility entity (FA2) may be any entity which provides a point of attachment on the macro mobility level, such as a mobility agent in Mobile IP type mobility management. If there is no mobility capability, a normal attach procedure is performed. However, if there is macro mobility capability, the access node (SGSN) selects a suitable mobility entity (FA2) to the mobile station (MS), sends the identity of the selected mobility entity to the mobile station and requests (8) the mobile station to initiate an activation of a packet protocol (PDP) context in the system.

Motion prediction in mobile/wireless networks

Abstract: This dissertation concerns the benefits of using mobility prediction to improve connection quality in wireless networks. A cellular wireless network consists of fixed based stations connected together by a wired network. Mobile terminals in a cellular network establish connections through their local base stations. There is a limit on the number of users that a base station can support simultaneously. Thus, an incoming connection is dropped when there is insufficient bandwidth in the current cell to support it. The number of ongoing connections that are dropped can be lowered by rejecting new call requests. One possible method of achieving this is to reserve bandwidth for a mobile terminal in a cell prior to its arrival. In this dissertation, reservation schemes that exploit mobility prediction to improve connection quality in cellular networks are investigated. Predictions are made on a mobile terminal's future location based on its previous history (i.e., the last cell that it has been in). Simulations for the prediction schemes are performed and the results are compared. Also, a cost function is developed to determine the efficiency of the schemes under investigation. Unlike cellular networks, an ad hoc network does not have any fixed communication infrastructure. For an active connection, the end hosts as well the intermediate nodes (which must act as routers in this case) are subject to mobility. Since the network topology is dynamic, data routes are subject to frequent disconnections. The research presented here exploits non-random mobility patterns that mobile users exhibit. Prediction of link connectivity is done by using Global Position Systems (GPS) and velocity vector information obtained from the mobile terminals. The predicted information is used to estimate the future state of network topology and perform route reconstruction pro-actively in a timely manner. In this research, mobility prediction enhancements are incorporated into various routing protocols for ad hoc networks. Simulations for the proposed enhancements are performed and the results are evaluated. The relationship between mobility speed and packet lost rate is also analyzed in this dissertation.

Mobility modeling and traffic analysis in three-dimensional high-rise building environments

Abstract: To efficiently plan future personal communications services, we need to solve various mobility/traffic problems in one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) micro- or pico-cell environments. Although many users exhibit vertical motion inside elevators in high-rise buildings, there have been no studies regarding cell planning which take into account vertical motion with elevators. We extend the previous 3-D indoor mobility modeling by considering the proper boundary conditions on each floor and vertical motions through elevators and modeling mobility in high-rise buildings in order to estimate the number of handoffs. We then propose a blocking probability model with mobility as a traffic model in 3-D indoor environments. Using this model, we can obtain the required number of channels per cell under the given blocking probability constraint. These results can be used in planning the networks of future personal communications services.

On the mobility of the austenite-ferrite interface in Fe-Co and Fe-Cu

Abstract: The kinetics of diffusional transformations in steels depend on a large number of parameters, such as grain geometry, nucleation behavior, and growth kinetics. An essential step in the process is the lattice transformation, the kinetics of which can be expressed by the mobility of the interface between the matrix and the newly forming phase. To study the intrinsic mobility of the austenite-ferrite interface, i.e., the mobility of the interface in the absence of long-range diffusion, differential thermal analysis (DTA) experiments were performed on high-purity dilute Fe-Co and Fe-Cu alloys. The data obtained were analyzed using a three-dimensional geometry, based on a tetrakaidecahedron model for the austenite grain and a recent interface mobility model. The observed transformation behavior is described accurately, with the interface mobility being composition dependent.

The implication of the next-generation wireless network design: cellular mobile IPv6

Abstract: The initiatives to add mobility to the Internet and packet data services for next-generation cellular systems are being considered by many mobile service providers. IPv6 is a new version of the Internet protocol that was standardized by the Internet Engineering Task Force (IETF). It supports mobility and is presently being standardized by the IETF Mobile IP Working Group. At the same time, cellular is an inevitable and developing architecture for the Personal Communication Service system (PCS). In this paper, cellular mobile IPv6 (CMI), a new algorithm that is migrated from mobile IPv6 is proposed for mobile nodes moving among small wireless cells at high speed. It is important for future mobile communication environments and should eventually, integrate its functions with the Internet. The purpose of this paper is to solve the problems of a communication break within smaller cellular coverage during high-speed movement with packet-switched data or the real-time voice messages. Thus, voice over IP (VoIP) packets were chosen to implement the system. Simulation results show smooth and non-breaking handoff during high-speed movement using the proposed algorithm.

Paging and location update algorithms for cellular systems

Abstract: Several alternative strategies for reducing paging and location update costs have been proposed lately. This paper initially compares four well-known strategies, that differ in the manner they approach that problem. The same mobility model and performance evaluation criteria were used for all strategies analyzed. Users are classified utilizing the call-to-mobility-ratio (CMR) metric. Results are given weighting in different ways the signaling cost in the radio interface and in the fixed network part. Based on the results obtained, this paper also introduces an alternative paging and location update algorithm. The subscriber call patterns and its mobility profile are used to define the size and shape of the location areas. Further analysis showed that this technique yields a significant signaling load reduction.

TeleMIP: Telecommunications-Enhanced Mobile IP Architecture for

Abstract: This article first surveys existing protocols for supporting IP mobility and then proposes an extension to the Mobile IP architecture, called TeleMIP. Our architecture attempts to achieve smaller handoff latency by localizing the scope of most location update messages within an administrative domain or a geographical region. TeleMIP is intended for use in evolving third-generation wireless networks, and introduces a new logical entity, called the mobility agent, which provides a mobile node with a stable point of attachment in a foreign network. While the MA is functionally similar to conventional foreign agents, it is located at a higher level in the network hierarchy than the subnet-specific FAs. Location updates for intradomain mobility are localized only up to the MA; transmission of global location updates are necessary only when the mobile changes administrative domains and/or geographical regions. By permitting the use of private or locally scoped addresses for handling intradomain mobility, TeleMIP allows efficient use of public address space. Also, by reducing the frequency of global update messages, our architecture overcomes several drawbacks of existing protocols, such as large latencies in location updates, higher likelihood of loss of binding update messages, and loss of inflight packets, and thus provides better mobility support for real-time services and applications. The dynamic creation of mobility agents (in TeleMIP) permits the use of load balancing schemes for the efficient management of network resources.

Integrating mobility prediction and resource pre-allocation into a home-proxy based wireless Internet framework

Abstract: This paper provides a novel home-proxy based framework which integrates the mobility management and QoS management techniques that have been adopted in the Internet environment. It then combines a mobility prediction and resource pre-allocation scheme with the above home-proxy based framework to provide an efficient mobility management environment capable of supporting real-time services. The viability and efficiency of the scheme is demonstrated through a simplistic analysis.

Evaluation of Constrained Mobility for Programmability in Network Management

Abstract: In recent years, a significant amount of research work has addressed the use of code mobility in network management. In this paper, we introduce first three aspects of code mobility and argue that constrained mobility offers a natural and easy approach to network management programmability. While mobile agent platforms can support constrained mobility in a rather heavyweight fashion, optimized approaches such as our CodeShell platform presented here can provide performance and scalability comparable to those of static distributed object platforms such as Java-RMI and CORBA. Properly implemented constrained mobility is thus of great importance in network management, resulting in flexible, extensible, programmable systems without prohibitive performance overheads.

Global internet roaming with ROAMIP

Abstract: Reachability and session continuity represent two distinct services that global mobility protocols should provide. Reachability is the possibility for Internet hosts to initiate sessions to mobile users. Session continuity refers to mechanisms that ensure that active transport or application layer sessions are not broken due to mobility. We present ROAMIP, a global mobility architecture that uses application layer solutions for global reachability and reuses transparent Mobile IP tunnelling mechanisms to ensure session continuity. ROAMIP eliminates long triangular routes, yet it is compatible with mobility unaware correspondent hosts. It is applicable to IPv6 as well as IPv4 networks. The ROAMIP architecture naturally lends itself to easy, gradual deployment and can reuse existing Mobile IP or SIP message formats. We conclude the paper by showing example traces from an experimental implementation.

Mobile RSVP with dynamic resource sharing

Abstract: We propose and analyze an extension of the concept of RSVP to guarantee the service quality of mobile Internet-based applications. Our Mobile RSVP protocol provides an advanced resource reservation mechanism in a wireless cellular environment. Furthermore, we propose the dynamic resource sharing algorithm to make better use of network resources in those cells, where advance reservation takes place. We analyze our proposed protocol and the corresponding dynamic resource sharing algorithm by simulating the behavior of distinct call types in a single cell. We also investigate the effect of user mobility behavior on the performance of future resource reservation protocols with mobility support. By analyzing the pattern of user mobility as well as possible application priorities, we hope to be able to put constraints to the scope of service provision.

Mobility modeling of rush hour traffic for location area design in cellular networks

Abstract: User mobility is one of the most important factors affecting the network performance in a cellular network. Increased mobility results in more location updates, handovers and hence an increase in the number of messages exchanged between various entities in the system. This signaling not only puts extra load on the radio interface but also on the infrastructure equipment. Thus, it is required to minimize the rate of occurrence of these mobility related events by optimally dividing the system into areas which have a minimum exchange of traffic. This paper presents a mobility model which can be used to predict the transient behavior of the traffic on the routes connecting these areas in a given network during rush hours when the capability of the network to handle mobility related signaling traffic is put to a severe test. Some algorithms which can use this information to optimally plan the network are also considered.

Quantum-mechanical 2D simulation of surface- and buried-channel p-MOS

Abstract: A two-dimensional MOS device simulator including quantum-mechanical effects has been developed and applied to surface- and buried-channel p-MOS devices. The Schrodinger equation is solved, retaining a large number of eigenstates, which are then used to build a modified classical distribution accounting for the high energy part of the distribution. With this approach, discontinuities in the gate capacitance near flat bands have been eliminated without introducing any empirical parameter. For accurate device simulation, experimental data on the hole mobility were collected, and a nonlocal mobility model was used for carriers in the bound levels. A standard mobility model is adopted instead for the classically-distributed carriers. Results are presented for the gate capacitance and drain current of 0.35 /spl mu/m p-MOSFET devices, showing a good agreement over a wide range of channel doping concentrations.

Tracking mobile users with uncertain parameters

Abstract: A method of reducing the wireless cost of tracking mobile users with uncertain parameters is developed in this paper. Such uncertainty arises naturally in wireless networks, since an efficient user tracking is based on a prediction of its future call and mobility parameters. The conventional approach based on dynamic tracking is not reliable in the sense that inaccurate prediction of the user mobility parameters may significantly reduce the tracking efficiency. Unfortunately, such uncertainty is unavoidable for mobile users, especially for bursty mobility pattern.In this study we propose a novel approach, which is efficient yet reliable. The basic idea is to incorporate a distributed scheme with a centralized scheme. The location update process incorporates a topology-independent distance based strategy and a load-sensitive timer. This combination forms a mechanism that bounds from above the total tracking cost. The registration activity is governed by the system, such that it increases at lowly loaded cells and decreases at heavily loaded cells.The expected wireless cost of tracking under the proposed method is significantly reduced, in comparison to the existing methods currently used in cellular networks. Furthermore, as opposed to other tracking methods, the worst case tracking cost is bounded from above and governed by the system. The proposed strategy can be easily implemented, and it does not require a significant computational power from the user.

Mobility model and performance analysis for zone-based registration in CDMA mobile communication system

Abstract: In this paper, we describe a mobility model and analysis for zone-based registration in the CDMA mobile communication system. We first propose a simple and proper mobility function for single zone-based registration. We establish the circumstances of multiple zone-based registration, which is based on the mobility function of single zone-based registration, and perform computer simulations for the circumstances. Using the simulation results, we obtain the optimal number of zones, N, that minimizes signaling traffic on radio channels. Results show that, in most cases, N is 2. We also show that multiple zone-based registration has lower signaling traffic on radio channels than single zone-based registration, and zone?based registration must be implemented as multiple zone?based registration.

Simulation of a Mobility Prediction Scheme Based on Neuro-Fuzzy Theory in Mobile Computing

Abstract: Mobility prediction is an important issue for efficient management in mobile computing. Whenever users move to a new location, mobile systems should know about their location change so that the connection is not in terrupted. In this paper, we focus on the simulation of a user mobility prediction scheme based on neuro-fuzzy theory. Our scheme predicts future locations from the movement patterns of users accumulated over several days or months, i.e., the user's location history. In or der to model users' movements, we use a neuro-fuzzy inference system. Whenever a user moves to a new lo cation, the system autonomously learns various move ment patterns. The prediction of the future location to which users will move is obtained by the approximate reasoning of the neuro-fuzzy inference system. This ap proach can derive an appropriate future location from learned location information, even if the mobile systems do not know the actual location history. Simulation re sults show that our prediction scheme has hig...