Akira Idoue

A media synchronization method for real-time group communication in a multiple device environment

This paper proposes a media synchronization method for real-time group communication within a multiple device environment. The method controls the output time of each media unit received at multiple devices and synchronizes them, even if the arrival time of the media unit temporarily fluctuates. This fluctuation is caused by variation in bandwidth and the network delay between different access networks. This paper also evaluates the system performance, in terms of aspects such as the average time of difference between the output and input times of each media unit, in order to confirm the effectiveness of the proposal.

Design of Protocol Monitor Emulating Behaviors of TCP/IP Protocols

Recently, the TCP/IP protocols are widely used and it is mentioned that, in some cases, throughput is limited due to problems such as network congestion. To solve such problems, the details of communication need to be examined. In order to support these examinations, we are developing an ‘intelligent’ protocol monitor which can estimate what communication has taken place by emulating the behaviors of the TCP protocol entities in a pair of communicating computers. This paper describes the overview of the monitor and the detailed design of the TCP behavior emulation function for both the state transition based behaviors and the internal procedures for the flow control, such as the slow start algorithm.

Adaptive channel and time allocation for body area networks

Personal health care is a promising application of a body area network (BAN). The BAN for health care application consists of a data collector and multiple wearable sensors that send data to the collector according to a sampling interval determined by the application. The data collector may be any hand-held or portable device such as a mobile phone, a PDA or a wristwatch. An individual user needs a BAN to detect, track or manage his/her health. Multiple BANs for such purpose are likely to appear in a nearby area, especially a place where population density is high. Since multiple BANs must share wireless medium in this scenario, a problem of packet collisions among BANs is unavoidable. To deal with such problem, this study proposes an adaptive scheme to allocate channel and time for coexisting BANs. The proposed scheme distinguishes inter-BAN and intra-BAN communications, and adaptively allocates channel and time according to the current number of BANs that exist in a nearby area. As a salient feature, the proposed scheme allocates time by attempting to satisfy the requirement of sampling interval determined by the application. The evaluation results demonstrate that our scheme achieves much higher packet delivery rate than the existing scheme.

Coordination path control method to reduce traffic load on NGN access gateway

Supporting Quality of Service (QoS) in a core transport is an important feature of a next generation network. This feature not only enables real-time communication services such as Voice over IP (VoIP) and video telephony, but also helps create new applications. However, access gateway such as Packet Data Gateway (PDG) in IMS WLAN Interworking, located at the edge of an IMS core network, must inspect all passing traffic tao support QoS, resulting in extensive concentration of network load on the access gateway. Moreover, the traffic control process in it must be performed according to various factors including a operator policy, service contracts, and network conditions, which increases the processing load. These negative factors increase the equipment cost of many access gateways to accommodate numerous users and their traffic. This paper proposes a path control method to reduce load concentration on the access gateway by offloading specified flows from PDG.

Resource Allocation for Coexisting ZigBee-Based Personal Area Networks

Personal healthcare is a promising market of a personal area network (PAN). The PAN consists of a data collector and multiple wearable sensors which must send data to the collector according to the frequency specified by each PAN. The data collector may be any hand-held or portable device, e.g., a mobile phone, a PDA, or a wristwatch. An individual user needs a PAN in order to detect, track, or manage his/her health. Multiple PANs for such purposes are likely to coexist in a same area, especially a place where a large number of users exist. Because multiple PANs must share resources (e.g., wireless channels, transmitting time) in this scenario, a problem of packet collisions among such PANs is unavoidable. As a result, the personal healthcare system using PAN cannot be provided as a service for the users because the data collector cannot collect sensing data from each sensor correctly. This paper proposes an adaptive scheme to allocate resources for coexisting PANs. The scheme distinguishes a PAN and a node when allocating resources such as wireless channel and transmitting time. Resources are dynamically allocated according to the current number of PANs that exist in the same area. In particular, the proposed scheme automatically reallocates resources when any PANs come into or leave from the coexisting area. As one of salient features, the scheme allocates transmitting time to meet a requirement on reporting interval determined by an application. Thus applications that are sensitive to delay can collect sensing data correctly and in time. The evaluation results show that our scheme achieves higher packet delivery rate than the standard ZigBee.

Interoperability Testing System of TCP/IP Based Communication Systems in Operational Environment

Recently, TCP/IP protocols are widely used. Here, although the protocols are realized in operating systems and users of communication systems pay no attention to their detail, some system errors are actually reported. Since those errors occur only in specific communication situations, the interoperability testing by watching communication by a testing system is appropriate to detect them. This interoperability testing has the following requirements. Firstly, since the system that includes system errors is not unidentified, the testing system needs to check all communication systems attached to a network. Secondly, for the similar reason, all protocols in the TCP/IP protocol stack need to be checked. Thirdly, the testing system needs to discriminate operational failures, such as server down and mis-configuration of parameters in clients, from system errors, when it detects any problems in the communication. Based on these considerations, we have designed an interoperability testing system of TCP/IP based communication systems applied in an operational environment. This paper describes the detailed design of our testing system and the testing algorithm for DHCP (Dynamic Host Configuration Protocol), for which some system errors are reported.

Dynamic Session Modification between Multiple Devices in the IMS/MMD Architecture

Multi-device communication will be usual in a ubiquitous networking environment with features of heterogeneity and ubiquity. Under such circumstances, users shall be able to communicate via a method optimized based on their surroundings and preferences. This paper shows a dynamic session modification mechanism that enables users to switch their communication resources via operation from remote devices during a session. With this in mind, the session manager and presence manager are introduced as application servers (AS) in IMS/MMD infrastructures. A prototype system, including implementation on a cellular phone, and performance evaluations are also shown.

A Novel Web Synchronization Method for Supporting Smooth Web Communication

Users employ various communication services such as browser-based remote assistance to support voice communication in a call center. However, there is an issue with web services regarding smooth communication due to out-of-synchronization of output time on browsers in an environment where network delay and rendering time fluctuates among devices. This status is perceived as being somewhat strange, or even irritating. Several methods have been studied to prevent out-of-synchronization for real-time services such as voice and video. We also target synchronization of browser operations (e.g. page movement) for web services. We propose a novel web synchronization method (WSM). WSM continues to synchronize the output time of web content among browsers. Synchronized output is realized by controlling the time to notify each browser of browser operations, and by controlling the time to send web content according to network delay and rendering performance. For usability, WSM is unnecessary for installing new software on a browser. We implemented a prototype system and measured the difference in the output time among browsers. The results show that WSM achieves web synchronization within about 300 ms (target time: 400 ms).

Proposal on network-wide rollback scheme for fast recovery from operator errors

This paper proposes a new network-wide rollback scheme for fast recovery from operator errors, toward the high availability of networks and services. A technical issue arises from the fact that operators, who manipulate one or more diverse devices and services due to their network-wide dependency in a typical management task, are the major cause of failure. The lack of systems or tools fully addressing the issue motivated us to develop a new scheme. The underlying idea is that, for any operational device or service, the observable behavior is identical whenever the same setting is configured. High availability will thus be achieved by rolling the settings that may cause an abnormal state by an operator error, back to past ones with which devices and services were stable. Certain policies for the network-wide rollback are identified and a prototype implementation and preliminary results will be presented.

Design of Intelligent OSI Protocol Monitor

As the OSI protocols come to be widely adopted in various communication systems, the testing of OSI protocol implementations becomes important. In this testing, the interoperability testing is performed to examine the interconnectability which cannot be checked in the conformance testing. In this paper, we propose the Intelligent OSI Protocol Monitor which observes PDUs (Protocol Data Units) exchanged between OSI system and analyzes the protocol behaviors as well as the PDU format according to the protocols of OSI 7 layers. This monitor is effectively used to observe the actual communication for a long period and to detect protocol errors which cannot be detected by the conformance testing. This paper describes the detailed design of the Intelligent OSI Protocol Monitor and shows how it works for actual OSI protocols.