Support User Mobility Research Articles

Agent-based user mobility support mechanism in RFID networking environment

In ubiquitous network environment, mobility is supported among various networks. When a user enjoying the media streaming service changes his attachment point, the service need to be provided continuously. In this paper, we propose a mechanism to provide seamless mobility for a user using RFID tag. We build a test bed for user mobility, and confirm that the seamless service can be provided according to the user movement. Also, we measure service delay time in case of moving a user to new access network.

Performance evaluation of planar antenna arrays onboard low earth orbit satellites

Earth orbit satellite (LEOS) systems offer continuous service using constellations, which stand out for their global coverage capacity, broadcast and ability to support user mobility. However, the low gain offered by omnidirectional antennas, as well as the large number of handovers within the satellite footprint due to the use of sector and spot beam antennas, along with the short satellite viewing time from the earth stations (ES), waste satellite power and degrades communications link quality. In this paper we present the use of a planar array antenna to establish communication links between LEOS and ES, allowing a more efficient use of satellite power and an increase in digital communications performance. The continuous steering of the antenna array radiation pattern (direction of arrival, DOA), adaptively directs the main lobe onboard the satellite towards the desired direction over the earth, allowing longer visibility time. A more directive downlink beam is obtained, increasing antenna gain and improving the bit error rate (BER) probability within quality of service (QoS) limits.

Design and Implementation of the DLNA Family Intercom System for Smart Homes

In a traditional intercom system that only allows place-to-place communication in a house, it is necessary to dial the extension number of a specific family member, or dial each extension number individually via the intercom broadcasting, in order to reach the desired person. Additional master stations controlled the intercom system are required, and it is load to maintain the stations for general users. In order to solve these problems, we propose the digital living network alliance (DLNA) compatible family intercom system (DFIS): the architecture to support user mobility. This architecture makes it possible to quickly reach a family member without the knowledge of the extension number that caters to a fixed location. In other words, it will be not necessary to dial the extension number of the location of the desired person. We introduce call control and phone handling under the subject of DFIS architecture and demonstrate that the proposed DLNA family intercom device and DLNA family intercom adaptor can work well.

On mobility-supporting transmit beamforming in MISO FDD wireless systems

When operating in frequency-division duplex (FDD) mode, transmit beamforming in multiple-input single-output (MISO) wireless communication systems typically requires accurate knowledge of downlink channel state information (CSI) at the transmitter. In practical FDD systems, obtaining such downlink CSI at the transmitter is challenging, if not impractical. To circumvent such challenge and support user mobility, we present a new method for transmit beamforming based on simple beam-control commands (BCCs) in MISO FDD mobile systems. We then numerically evaluate the effects of BCC errors in terms of transmit power efficiency, system capacity, and outage probability.

A QoS WMN with mobility support

We present QMesh, a software package that allows utilizing multiple geographically scattered Windows desktops as a wireless mesh network infrastructure with seamless user mobility support. QMesh supports its users through standard protocols, and does not require any client software installation. We optimize the solution's quality of service (QoS) by providing a centralized management infrastructure, which allows an assignment of users to Internet gateways that balances between distance and load considerations. QMesh is implemented as a Windows XP driver, on top of the Mesh Connectivity Layer (MCL) toolkit from Microsoft Research that provides basic routing capabilities. To the best of our knowledge, this is the first mobile mesh solution implemented within the Win32 kernel space.

Mykil : A Secure and Highly Available Key Management System Forlarge Group Multicast

This paper describes the design, implementation and evaluation of Mykil, a new key management system for supporting secure group multicast. Mykil was developed on a combination of group-based hierarchy and key-based hierarchy systems for secure group key management. The advantages of Mykil include a fast and efficient rekeying operation for large group sizes, continuous availability of the key management service in a disconnected network environment, an ability to map group structure to the underlying network infrastructure, and support for user mobility and smaller, hand-held devices. A prototype of Mykil has been implemented. The paper describes this implementation and reports on the performance measured.

Design of a SIP-based real-time visitor communication and door control architecture using a home gateway

Though typical video door phone systems can be used to talk to the visitors at the door, they have some shortcomings: the resident should stay in house and he/she is not informed of any visitor information on his/her return to home. To overcome these limitations, we propose an architecture supporting user mobility, with which the resident at anywhere can view and converse with a visitor at the front door using PCs, PDA's and home servers with Internet connections. We implemented the proposed architecture using SIP (session initiation protocol) and a home gateway system connected to a conventional intercom or a video door phone system.

Evaluation of a mobile IPv6-based architecture supporting user mobility QoS and AAAC in heterogeneous networks

This paper presents a Mobile IPv6-based overlay network architecture for heterogeneous environments, designed entirely based on IPv6, that aims to be implemented seamlessly irrespectively of the supporting network infrastructure. All transmission technologies are handled at the physical and data-link layers, imposing IPv6-based protocols for all higher layer communications and signaling. The architecture builds on Mobile IPv6 including improved fast handover, and integrates quality-of-service and authentication, authorization, accounting, and charging control per user. The most critical issues of the proposed architecture, mainly related to the handover process, were subject of a performance evaluation via ns-2 simulations. Finally, a field trial of the system was implemented, overlaying part of the GEANT infrastructure between Madrid and Stuttgart, which results are presented here.

Aviation Data Networks

Aircraft data networks are fast becoming more of a necessity due to their support for user mobility. Many aircraft manufacturers are planning to deploy data networks within their airplanes and provide internet connectivity to their passengers. While a data network within the aircraft and passenger access to it causes some security concerns, it open up some safety enhancement opportunities. With internet connectivity within the airplane, the activity within the airplane can be monitored in real-time from the ground station. Also, using the high bandwidth satellite links, the flight critical data could be downloaded to a server in the ground station in real-time flight or periodically, thereby enabling real-time flight status monitoring. The information technology (IT) revolution, combined with people’s need to access information quickly, has resulted in the explosive growth of the Internet in the past decade. An integrated security framework requires a careful consideration of the security features of the network within an airplane. Potentially, the aircraft could consist of three kinds of networks namely passenger network, crew network and control network. The security protocol implemented must ensure a proper separation of these networks and also watch for any security protocol violations. Ill. 5, bibl. 4 (in English; summaries in Lithuanian, English and Russian).

Proactive context transfer and forced handover in IEEE 802.11 wireless LAN based access networks

In recent years, many protocols have been developed to support user mobility in wireless networks, e.g. Mobile IP suite of protocols designed to support IP routing to mobile nodes. However, support for truly seamless mobility requires more than just routing: every service associated with the mobile user needs to be transferred smoothly to the new access network. In this paper, we will concentrate on the problem of transferring service state (context) at both the link and the IP layers. We propose a method to estimate the best moment in time for transferring context information associated with the mobile user. As one of key issues in the proactive context transfer scheme is accuracy of handover prediction, we suggest and describe a new concept of Forced Handover that can provide very low handover latency. The simulation results and the following discussions show that our scheme is helpful in ensuring seamless mobility, while keeping the number of unnecessary handovers resulting from the proactive nature of the scheme at a controllable level.

Supporting User Mobility through Cache Relocation

Traffic and access delay can be reduced in a mobile network by caching data objects at network nodes near the clients. Traditional caching techniques, however, are unsuitable in this environment because they do not account for the changing location of the users. To deal with this problem, cache relocation techniques can be applied to dynamically relocate data objects so they remain close to the moving clients. Existing relocation techniques rely heavily on path prediction. Unfortunately, the inaccuracy of path prediction can lead to high relocation overhead and poor response time. This paper presents an analytical study of the effects of client mobility on network cache performance. Two new cache relocation techniques are proposed to deal with the issue of poor path prediction and reduce the overhead of existing cache relocation schemes. The first technique, 2PR, compensates for poor path prediction by temporarily moving data objects to a common parent node prior to a handover. Objects are moved to the correct destination once the client′s new location has been confirmed. The second technique, ROLP, reduces the traffic overhead associated with cache relocation by ensuring duplicate objects are not relocated and relocation of objects are performed only from the nearest node to the destination. Test results show that 2PR reduces the query delay experienced by mobile clients by 60 to 83% after handovers, while ROLP reduces the overhead of cache relocation by between 33 to 65% compared to existing schemes.

Seamless User-Level Handoff in Ubiquitous Multimedia Service Delivery

Advancing mobile computing technologies are enabling “ubiquitous personal computing environment”. In this paper, we focus on an important problem in such environment: user mobility. In the case of user mobility, a user is free to access his/her personalized service at anytime, anywhere, through any possible mobile/fixed devices. Providing mobility support in this scenario poses a series of challenges. The most essential problem is to preserve the user's access to the same service despite changes of the accessing host or service provider. Existing system-level mobility solutions are insufficient to address this issue since it is not aware of the application semantics. On the other hand, making each application to be mobility-aware will greatly increase the development overhead. We argue that the middleware layer is the best place to address this problem. On one hand, it is aware of application semantics. On the other hand, by building application-neutral mobility functions in the middleware layer, we eliminate the need to make each application mobility-aware. In this paper, we design a middleware framework to support user mobility in the ubiquitous computing environment. Its major mobility functions include user-level handoff management and service instantiation across heterogeneous computing platforms. We validate the major mobility functions using our prototype middleware system, and test them on two multimedia applications (Mobile Video Player and Mobile Audio Player). To maximally approximate the real-world user-mobility scenario, we have conducted experiments on a variety of computing platforms and communication paradigms, ranging from T1-connected high-end PC to handheld devices with wireless networks. The results show that our middleware framework is able to provide efficient user mobility support in the heterogeneous computing environment.

User mobility support in an urban CDMA-based wireless network

A salient feature of wireless networks is the ability to support user roaming. However, user mobility has a profound effect on grade of service (GoS) and quality of service (QoS) provisioning. Code division multiple access (CDMA) is the multiple access technology for the third-generation wireless standard (3G) and is envisioned to be the multiple access technology beyond 3G. CDMA is interference-limited. The signal-to-interference (SIR) ratio, expressible in the form of Eb/I0, is an important parameter in CDMA systems and has a profound effect on the system capacity. The system capacity in turn affects the call-level GoS of the network layer in terms of new call blocking probability and forced termination probability. The effect of user mobility on (i) degradation in utilization and (ii) excess capacity needed to satisfy the QoS/GoS requirements, in an urban environment, is examined and quantified. A relationship between the link-layer Eb/I0 specification and the call-level GoS parameters in the presence of user mobility is also established. Numerical results which display the linkages between the link-layer QoS and call-level GoS parameters are presented and discussed. This coupling gives a quantification of the link-layer requirement to provision the call-level GoS, in the presence of user mobility.

Fast handoff scheme based on mobility prediction in public wireless LAN systems

Recently, wireless LAN systems have been widely deployed for public mobile Internet services. Public wireless LAN systems can provide high speed Internet connectivity using portable devices such as laptop computers, personal digital assistants (PDAs), etc. In public wireless LAN systems, reliable user authentication and mobility support are essential issues. However, re-authentication during handoff procedures causes long handoff latency and this affects the quality of service in real-time multimedia applications. A fast handoff scheme based on mobility prediction is proposed. In this scheme, a mobile host entering the area covered by an access point (AP) performs authentication procedures for multiple APs, rather than just the current AP. These multiple APs are selected by a prediction method called the frequent handoff region (FHR) selection algorithm, which takes into account users' mobility patterns, service classes, etc. Since a mobile host is registered and authenticated for an FHR in advance, handoff latency resulting from re-authentication can be significantly reduced. Simulation results show that the proposed scheme is more efficient than other schemes in terms of handoff delay and buffer requirements.

A fast rerouting scheme using reservation in wireless ATM

With growing demand for higher bandwidth multimedia services in the wireless domain over the past few years, wireless asynchronous transfer mode (ATM) has emerged as a fine solution. Wireless ATM provides mobility support for mobile ATM users as they move among base stations. One of the key issues to support user mobility is the handoff. For a relatively smaller cell environment in wireless ATM, a handoff scheme should exhibit low handoff delay. Efficient usage of network resources is also required. We propose a fast rerouting scheme for wireless ATM; it is referred to as a path reservation scheme. For localized handoffs, we adopt a wireless cell clustering method. Cell grouping and a path reservation technique are proposed to achieve fast handoffs. The paper presents an analysis of the proposed scheme and simulation results of several handoff schemes compared with the proposed scheme. From the simulation results, our path reservation scheme achieves low handoff delay and efficient usage of network resources such as buffer and bandwidth requirements.

A network infrastructure for IP mobility support in metropolitan areas

The original design of the Internet and its underlying protocols did not anticipate users to be mobile. With the growing interest in supporting mobile users and mobile computing, a great deal of work is taking place to solve this problem. For a solution to be practical, it has to integrate easily with existing Internet infrastructure and protocols, and offer an adequate migration path toward what might represent the ultimate solution. In that respect, the solution has to be incrementally scalable to handle a large number of mobile users and wide geographical scopes, and well performing so as to support all application requirements including voice and video communications and a wide range of mobility speeds. In this paper, we present a survey of the state-of-the-art and propose a scalable infrastructure to support mobility in Internet protocol networks. In that respect, we exploit local area network (LAN) technologies to create the network infrastructure necessary to offer connectivity to mobile users across any geographical area (building, campus and metropolis). The intrinsic properties of LAN technologies and their underlying protocols, namely flat address space, transparent learning and low complexity renders this solution particularly cost effective for supporting user mobility. In particular, we propose a network topology and a set of protocols that render the infrastructure scalable to a large geographical area and many users.

Performance of wideband CDMA systems supporting multimedia traffic

We evaluate the performance of wideband CDMA cellular systems providing different classes of multimedia traffic and supporting user mobility. A Markovian teletraffic model of the user dynamics is developed. Constraints are imposed in the model which account for the multiple access interference among active users. Results are shown in terms of call blocking probabilities and average number of active connections. The methodology proposed is a useful tool for the design and planning of third generation cellular systems.

MC2 platform supporting mobile computing and communication

Mobile computing, in which a small computer connected to a computer network by means of a mobile communication network can be carried by the user, is becoming possible. In the mobile computing environment, there occur problems specific to wireless communication that are not experienced in wired networks, such as disconnection of the communication channel and inability to make a connection. Also, the user may use computers other than his own portable one, depending on the location. In this paper, an agent platform that takes into account the characteristics of mobile computing is proposed. The proposed platform supplements the deficiencies of the wireless communication and provides an environment in which agents that support user mobility are available. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(11): 63–72, 1999

Untraceable mobility or how to travel incognito

User mobility is rapidly becoming an important and popular network feature. This is especially evident in wireless/cellular networks where user mobility raises a number of important security issues and concerns. Foremost among them is the ability to track mobile users' movements and whereabouts. Ideally, no entity other than the user himself and a responsible authority in the user's home domain (if any) should know both the real identity and the current location of the mobile user. At present, most environments supporting user mobility either do not address the problem at all or base their solutions on assumptions that are specific to today's cellular phone networks. This paper discusses a number of issues related to anonymity and location privacy in mobile networks. It reviews current state-of-the-art approaches, identifies their exposures of anonymity and proposes several low-cost solutions which vary in complexity, degree of protection and assumptions about the underlying environment.

Defining Open Software Architectures for Customized Remote Execution of Web Agents

Agent-based solutions promise to ameliorate Web services, by promoting the modular construction of Web servers, relieving the network from transferring useless data, supporting user mobility, etc. However, existing Web servers do not favor the hosting of agents. This paper proposes a description of agent behavior in terms of its requirements regarding resource utilization (e.g. memory, and disk space), functional services (e.g. system calls), and non-functional properties (e.g. degree of replication, and access control). When formally expressed, these requirements can be used in an automated decision process, which is based on software specification matching techniques. Upon the acceptance of an agent, the host uses these requirements to construct an environment customized to agent's execution. We discuss the benefits of this approach, and how it can be used to promote existing agent-based solutions in the Web framework.