Next-generation wireless/mobile networks will be IP-based cellular networks integrating Internet with the existing cellular networks. Recently, Hierarchical Mobile IPv6 (HMIPv6) was proposed by the Internet Engineering Task Force (IETF) for efficient mobility management. HMIPv6 reduces the amount of signaling and improves the performance of MIPv6 in terms of handoff latency. Although HMIPv6 is an efficient scheme, the performance of wireless networks is highly dependent on various system parameters such as user mobility model, packet arrival pattern, etc. Therefore, it is essential to analyze the network performance when HMIPv6 is deployed in IP-based cellular networks. In this paper, we develop two analytic models for the performance analysis of HMIPv6 in IP-based cellular networks, which are based on the random-walk and the fluid-flow models. Based on these analytic models, we formulate the location update cost and the packet delivery cost. Then, we analyze the impact of cell residence time and user population on the location update cost and the packet delivery cost, respectively. In addition, we study the variation of the total cost as the session-to-mobility ratio is changed and the optimal MAP domain size to minimize the total cost is also investigated.

This paper presents a new mobility protocol that supports multiple namespaces on IPv6 networks. Our proposed protocol framework allows a mobile node to specify a correspondent node by a name that is defined in any namespace as a node identifier. This technique removes certain restrictions on the space of node identifiers and allows mobile nodes to communicate with each other regardless of their location. Mobile nodes negotiate a pseudo node identifier, which is unique between the two nodes, with a correspondent node that is identified by the name. We make this pseudo node identifier compatible with the IPv6 address format; we can thus use existing IPv6 applications with our proposed mobility framework. This framework is based on Location Independent Network Architecture (LINA), and provides mobility support in a simple fashion and with low protocol overhead. We also demonstrate how to provide anonymity to our mobility protocol by using a dynamic pseudo node identifier. Our prototype implementation shows minimal overhead compared to a conventional IPv6 implementation.

Resulting from the spread of Mobile Internet, the mobile communication with QoS guarantee will be required in order to realize mobile video interactions. So far, there are some studies focusing on QoS Mobile IP communication, but they require backbone routers to maintain per-flow QoS information for all individual Mobile Nodes. So these approaches suffer from the lack of scalability. Against them, we are developing an approach which the per-flow QoS information is maintained only by Mobile IP agents such as the Home Agent and the Foreign Agent. We have adopted a hierarchical method with MPLS which MPLS paths with large bandwidth are introduced between Mobile IP related nodes, and a per-flow path with small bandwidth called Pathlet is established for individual communication between a Mobile Node and a Fixed Host. The maintenance of Pathlets is only performed by Home Agent, Foreign Agent and Fixed Host, and the network backbone MPLS routers only take care of MPLS paths with large bandwidth. In the simulation, we compare our scheme with conventional scheme by observing the total number of entries managed by routers and bandwidth prepared at individual links.

The exciting goals of ubiquitous computing and communication services can only be achieved if we can increase the efficiency with which the location of mobile terminals can be managed; current mobile infrastructures are not efficient since they treat all mobile terminals uniformly despite that fact that many mobiles often move together (i.e. passengers on the same train or a group of cars on a road). This paper presents a hierarchical location management scheme that handles such grouped mobiles collectively and so reduces the overhead costs of location management. In our scheme, mobiles that move together for long enough form a mobile network and make a hierarchy in the wireless access network. The scheme also adjusts the number of mobile networks to keep communication overhead low. We apply the scheme to Mobile IPv6 and evaluate the resulting performance improvement. Simulation results confirm that our hierarchical approach can greatly reduce the overhead costs of location management, and that it is very practical since it can flexibly develop suitable mobile networks.

Channel estimation is one of the key technologies in mobile communications. Channel estimation is critical in providing high data rate services and to overcome fast fading in very high-speed mobile communications. This paper presents a novel channel estimation based on hybrid spreading of I and Q signals (CEHS). Simulation results show that it can effectively mitigate the influence of fast fading and enable to provide high data rates for very high speed mobile systems.

SMIL is a markup language which enables us to describe multimedia contents. This paper proposes a design model of SMIL browser functionality for mobile phones whose resources are limited. We introduce SMIL Component, which is based on attachable software architecture to a pre-installed generic web browser and an event-based SMIL scheduler, which is a part of SMIL Component, to provide the multimedia presentation scheduling functionality. These lead to reducing the memory amount that SMIL Component consumes and brings high portabilty of SMIL Component for various web browsers. We implement SMIL Component and evaluate RAM sizes and presentation delays. As a result, we conclude that SMIL Component is practical for MMS presentations on a mobile phone.

The authors have performed a simple computer simulation for a topography that models change in propagation characteristics due to change in traffic volume. The results of this simulation revealed that path loss for a traffic volume of about 2000 vehicles every 30 minutes in a typical urban environment exhibits a Rayleigh distribution. This result agrees well with that of actual measurements demonstrating that even a simple simulation can be a useful tool in system design.

A mobile ad hoc network (MANET) is characterized by multi-hop wireless links in the absence of any cellular infrastructure as well as by frequent host mobility. This paper proposes a SMPQ: Spiral-Multi-Path QoS routing protocol in a MANET, while the MAC sub-layer adopts the CDMA-over-TDMA channel model. This work investigates the bandwidth reservation problem of on-demand QoS routing in a wireless mobile ad-hoc network. The proposed approach increases the ability of a route to identify a robust path, namely a spiral-multi-path, from source host to destination host, in a MANET to satisfy certain bandwidth requirements. Two important contributions of the proposed spiral-multi-path are: (1) the spiral-multi-path strengthens route-robustness and route-stability properties and (2) the spiral-multi-path increases the success rate of finding the QoS route. Performance analysis results demonstrate that our SMPQ protocol outperforms other protocols.

This paper outlines the perspectives on Software Defined Radio (SDR) technology in viewpoint of the standardization of the future mobile communication systems. The activities of ITU-R SG8 Working Party 8F (WP8F) and mITF (mobile IT Forum) of Japan for systems beyond IMT-2000 (B3G) or 4-th generation mobile systems are firstly summarized. The latest discussions relating to SDR technology in the both parties are reported. It is followed by consideration on both expectations and technical issues on SDR in order to realize the technology in the future mobile communication systems. They are clarified in the viewpoint of standardization activity on B3G. Also some regulation issues are lastly summarized.

The Communications Research Laboratory (CRL) started a new project named the New Generation Mobile Network Project in April 2002. The target of this project is the development of new technologies to enable seamless and secure integration of various wireless access networks such as 3rd and 4th generation cellular, wireless LAN, high-speed mobile wireless, wired communications, and broadcasting networks. This paper presents an overview of CRL's new generation mobile communication system that is called The Multimedia Integrated Network by Radio Access Innovation Plus (MIRAI+), as well as details the role of Software Radio Technology (SDR) in MIRAI+.

Fault-tolerant execution of a mobile agent is an important design issue to build a reliable mobile agent system. Several fault-tolerant schemes for a single agent system have been proposed, however, there has been little research result on the multi-agent system. For the cooperating mobile agents, fault-tolerant schemes should consider the inter-agent dependency as well as the mobility; and try to localize the effect of a failure. In this paper, we investigate properties of inter-agent dependency and agent mobility; and then characterize rollback propagation caused by the dependency and the mobility. We then suggest some schemes to localize rollback propagation.

This paper presents a framework for building mobile agent-based components. The framework introduces the notion of agent hierarchy and inter-agent migration and thus allows a group of mobile agents to be dynamically assembled into a single mobile agent. It provides a powerful method of constructing complex, large-scale mobile agent-based applications. To demonstrate how to exploit our framework, we construct an extensible and portable mobile agent system for executing and migrating hierarchical mobile agents. The system itself is also implemented as a collection of mobile agents and can thus dynamically change and adapt its functions through migrating agents that offer the functions. Mobile agent-based applications running on the system can naturally inherit the extensibility and adaptability of the system.

A mathematical expression for the received signal power in a severe frequency-selective fading channel is derived. Using the derived expression, the signal power distributions are obtained by Monte-Carlo simulation and compared with the Nakagami m-power distribution. It is found that the power distribution matches well with the Nakagami m-power distribution when the multipath channel has a uniform power delay profile.

We propose an effective method to localize a maneuvering mobile station by means of fixed base stations using the interacting multiple model (IMM) supporting the geometry-based localization algorithms. Representative performance analysis confirms that the proposed IMM solution significantly reduces location error and is better than that of Kalman filter implementation.

The performance of a mobile ad hoc network (MANET) is related to the efficiency of the routing protocol in adapting to changes in the network topology and the link status. However, the use of many different mobility models without a unified quantitative "measure" of the mobility has made it very difficult to compare the results of independent performance studies of routing protocols. In this paper, a mobility measure for MANETs is proposed that is flexible and consistent. It is flexible because one can customize the definition of mobility using a remoteness function. It is consistent because it has a linear relationship with the rate at which links are established or broken for a wide range of network scenarios. This consistency is the strength of the proposed mobility measure because the mobility measure reliably represents the link change rate regardless of network scenarios.

The QoS(Quality of Service) guarantee mechanism is one of critical issues in the wireless network. Real-time applications like VoIP(Voice over IP) in All-IP networks need smooth handoffs in order to minimize or eliminate datagram loss as a Mobile Host(MH) transitions between network links. In this paper, we design a new DB(Dynamic Buffering) mechanism for IPv6 by which an MH can request that the router on its current subnet buffers packets on its behalf while the MH completes registration procedures with the router of a new subnet. Performance results show that our proposed buffering scheme with a dynamic buffer space allocation is quite appropriate for mobile Internet, or the All-IP environment in terms of the datagram loss rate and average waiting time.

Recently, in wired networks, a hierarchical structure has been introduced to improve management and routing. In ad hoc networks, we introduce a hierarchical structure to achieve the same goal. However, it is difficult to introduce the hierarchical structure because all mobile hosts are always moving around the network. So, we proposed the clustering scheme to construct the hierarchical structure before. In this paper, we propose a new hierarchical routing protocol called Hi-TORA based on the clustering scheme. And we show the experimental evaluation of Hi-TORA with respect to the number of control packets, accuracy of packet delivery and hop counts in comparison with TORA.

Information service provision and utilization is an important infrastructure in the high-assurance distributed information service system. In order to cope with the rapidly evolving situations of providers' and users' heterogeneous requirements, one autonomous information service system has been proposed, called Faded Information Field (FIF). FIF is a distributed information service system architecture, sustained by push/pull mobile agents, through a recursive demand-oriented provision of the most popular information closer to the users to make a tradeoff between the cost of service allocation and access. In this system, users' requests are autonomously driven by pull mobile agents in charge of finding the relevant service. In the case of a mono-service request, the system is designed to reduce the time needed for users to access the information and to preserve the consistency of the replicas. However, when the user requests joint selection of multiple services, synchronization of atomic actions and timeliness have to be assured by the system. In this paper, the relationship that exists among the contents, properties and access ratios of information services is clarified. Based on these factors, the ratio of correlation and degree of satisfaction are defined and the autonomous integration and optimal allocation of information services for heterogeneous FIFs to provide one-stop service for users' multi-service requirements are proposed. The effectiveness of the proposed technology is shown through evaluation and the results show that the integrated services can reduce the total users access time and increase services consumption compared with separate systems.

Broadcast disks are suited for disseminating information to a large number of clients in mobile computing environments. In broadcast disks, the server continuously and repeatedly broadcasts all data items in the database to clients without specific requests. The clients monitor the broadcast channel and read data items as they arrive on the broadcast channel. The broadcast channel then becomes a disk from which clients can read data items. In this paper, we propose a cache conscious concurrency control (C4) algorithm to preserve the consistency of read-only client transactions, when the values of broadcast data items are updated at the server. The C4 algorithm is novel in the sense that it can reduce the response time of client transactions with minimal control information to be broadcast from the server. This is achieved by the judicious caching strategy of the client and by adjusting the currency of data items read by the client.

This paper proposes a framework for building a reusable mobile agent from two kinds of components: an itinerary component and an application-specific logic component. Both components are implemented as mobile agents. The former is a carrier of the latter over particular networks and the latter defines management tasks performed at each host independently of the network. This framework also provides a mechanism for matchmaking the two mobile agent-based components. Since the mechanism is formulated based on a process algebra approach, it can strictly select a suitable itinerary component to perform management tasks at the hosts that the tasks want to visit over the networks. A prototype implementation of this framework and its application were built on a Java-based mobile agent system. We summarize the lessons learned while formalizing and implementing the approach and we compare it to related work.