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Conventionally, the problem of capacity-flow assignment in packet switching computer networks has been considered mainly for the purpose of improving the network performance and the effective usage of the resources in the networks. The problem of the fair allocation of the network resources to each user (fairness) has been investigated little. Because one of the most important purposes of the computer network is that a plural number are arranged dispersively in the network, we must make sufficient study of fairness in the problem of the flow assignment of the packet and the problem of the distribution of the line capacity. However, no clear definition of the fair allocation has been proposed to data. In this paper, we adopt the "power" (function) as the performance measure and discuss the problem of the network capacity-flow assignment in which maximized network power ensures effective usage of networks, and equalized power for each user realizes the fairness. The results of this study provide a new guideline to solve the problem of distributing the resources effectively and fairly. The method in this paper can be discussed generally without limitation of the network topology. However, since the concrete numerical calculation is so complicated, we take loop networks for the object of the analysis. [ABSTRACT FROM AUTHOR]

In the video and speech transmission using packets, the media synchronization control is applied, especially in the system for real-time transmission. In the system containing the media synchronization, the allowable time delay is defined, and the packet after this delay limit is discarded. In protocols such as ARQ (automated repeat request), where the packet retransmission is executed for error correction, if the delay or the error rate of the channel is large, the packet delay is greatly increased when an error occurs. The packet is discarded when the packet delay exceeds the allowable delay, which produces degradation of quality. This paper proposes an adaptive protocol relay system considering the allowable delay, in order to cope with this problem. In the adaptive protocol relay system, the protocol relay is executed at the relay node, when a certain condition for each packet is satisfied. By reducing the time spent in the packet retransmission due to the error, the number of packets that do not arrive at the receiving terminal within the allowable delay is reduced. This paper examines the effect of the protocol relay on the packet discard rate, when the proposed method is used. The condition for the adaptive control at the relay node is also discussed. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(8): 50–59, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10031 [ABSTRACT FROM AUTHOR]

FRN (flexible radio network) is an ad hoc network product that can realize a wide-area data collection network. This paper discusses a performance improvement method when TCP is applied to the transport layer in FRN. It is shown that even when the terminal is not moving as in FRN, the throughput can be improved in radio link failure due to noise or obstacles by combining ELFN (explicit link failure notification), which is proposed as a method for TCP performance improvement in ad hoc networks, with routing information. The proposed method is evaluated by simulation in this paper. A further objective is to reduce the performance degradation due to packet collision. The delayed ACK and the ACK retransmission with priority in the case of packet collisions are analyzed and the effectiveness of the method is demonstrated. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 99–107, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10134 [ABSTRACT FROM AUTHOR]

In cellular communication systems, every call is carried through a base station, and when the communication path to the base station is obstructed by buildings or other obstacles, the communication may not be established. It is expected that ad hoc relaying of such an obstructed call will increase the performance of the network as a whole. This paper discusses how to theoretically analyze the communication traffic performance of a cellular system with ad hoc networking and shows that the network performance can be increased even with relatively small range of relaying capability of terminals. This paper also shows by simulation that multihop relaying does not give significantly greater performance improvement than that by two-hop relaying. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 1–10, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10135 [ABSTRACT FROM AUTHOR]

Self-healing has been investigated as a technique for efficient path failure restoration in VP-based networks. This paper discusses self-healing in networks with multiple reliability classes, and evaluates restoration performance of different failure recovery procedures that introduce priority orders in the failure recovery process based on the reliability class for each failed path. The authors present a composite-type restoration procedure in which preplanned-type and flooding-type procedures are combined. This paper also presents a bumping added-type restoration procedure. The authors evaluated the performance of the above proposed techniques assuming various failure modes. The simulation results revealed that the proposed methods show improved performance. In addition, we propose an enhanced technique that introduces a subsidiary priority criterion in the paths belonging to the same reliability class, in order to increase the number of paths to be recovered. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(7): 1–17, 2001 [ABSTRACT FROM AUTHOR]

This paper presents a new construction of the distributively controlled homogeneous self-routing space switch network, which is composed of single-kind 2 x 2 unit modules. The feature of the proposed method is that the order is defined among the destination addresses according to their binary representation by the bitwise comparison. The bionic sort is executed based on the order. In the conventional space switch network composed of a single kind of module, the total number of unit modules is of the order of N2 at the minimum, where N is the number of I/O ports. In the space switch network proposed in this paper, the total number of unit modules is of the order of (N log3N). The total number of unit modules in the proposed method is equal to that of the conventional method for N>16. When N = 1024, for example, the total number of unit modules in the proposed method is approximately one-sixth that of the conventional method. Another point is that the processing speed within the 2 x 2 unit module is independent of N, as in the conventional method, and is small. This is advantageous in the high-speed operation. [ABSTRACT FROM AUTHOR]

In multicast delivery in a network environment with various bandwidth limitations, it is effective to apply the layered multicast technique, which realizes delivery at a reception rate matched to each receiver, although the rate is set discretely. This paper assumes a multimedia session such as a multichannel broadcast or a video conference, composed of multiple streams. In such an application, it is desirable from the viewpoint of efficient use of bandwidth that not only should the streams be transmitted with stable quality, but that the rate should be assigned according to requests, such as attention to the speaker. However, it is difficult to achieve the above goal by directly applying the conventional layered multicast rate control technique, since each stream controls the rate independently. From such a viewpoint, this paper presents a session level mechanism covering multiple layered streams. A multiple streams controller (MSC) is introduced into each receiver, and each MSC autonomously controls the reception rate with interstream coordination in the session. The MSC monitors the reception state of the multiple streams simultaneously and estimates the bandwidth information on the bottleneck link and the set of transiting streams, based on the detected congestion data. Based on the estimation, the learning efficiency of the reception rate is improved and rate assignment control over the streams is applied. An evaluation is performed by computer simulation, and it is shown that the reception quality of the stream is improved by applying the proposed method, and that the reception rate can be coordinated among the streams. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(8): 18–31, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20142 [ABSTRACT FROM AUTHOR]

This paper considers the ubiquitous environment, in which a tremendous number of objects, such as physical devices, multimedia contents, and software components, exist everywhere. In order to provide and utilize various services transparently in such an environment, there must be a service synthesis technique that can dynamically construct services by mutually connecting objects. The realization of service synthesis requires a position-independent naming service which can securely and transparently call from the network the functions (functional objects) that act as the service component. The authors designed an interface-based naming service which can perform transparent calling of functional objects on the basis of interface information on the objects. The interface-based naming service not only can call functional objects efficiently from the network, but also can provide several useful features of service synthesis support: when two functional objects are interconnected, the required supplementary functional object is automatically determined, and when a function cannot be found, that function is realized equivalently by using multiple functional objects. This paper describes the architecture of the interface-based naming service, together with its algorithm. The approach is evaluated by simulation and it is shown that the interface-based naming service is a useful system in a ubiquitous environment with an increased number of objects and an enlarged network scale. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(3): 63–75, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10177 [ABSTRACT FROM AUTHOR]

In reliable multicast, the same information is transmitted to specified receiving nodes while maintaining reliability, with the information rate aligned to the receiving node with the lowest throughput by end-to-end control. However, the consideration of the receiving node with the lowest throughput produces the problem that other receiving nodes belonging to the same multicast group are limited to a considerably lower throughput than their own reception limits. This is a problem inherent to multicast communications, where the receiving nodes generally differ in congestion status. This fairness problem for receiving nodes is called intrasession fairness. In reliable multicast, it is impossible to realize intrasession fairness by using only end-to-end control. The purpose of this paper is to realize intrasession fairness by a scheme in which servers independently apply congestion control to the downlink by placing servers in the network and providing network support. The proposed scheme is evaluated by simulation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10125 [ABSTRACT FROM AUTHOR]

Channel efficiency can be improved by transmission that integrates voice and the data. When this idea is applied to multicellular systems, channels must be assigned so that the intercellular interference power is minimized. Furthermore, channels must be provided with priority for voice calls, since real-time transmission is required. As a system that considers these requirements, this paper investigates a method of reducing intercellular interference in a circuit switching system with channel segregation in which data are transmitted with priority, using the silent period of voice calls. It is shown by computer simulation that the proposed method can improve performance characteristics such as the interference rate, blocking rate, forced termination rate, and hand-off rate. [ABSTRACT FROM AUTHOR]