Cache technology (e.g., P2P, CDN, web proxy, and ICN/CCN) is used for file duplication and load balancing in a file delivery system. In these systems, service latency when customers send requests and receive files is very important in file content delivery for customer satisfaction. Optimal file delivery scheduling to minimize the latency in a one-link model has already been proposed, so in this paper, we study the scheduling with fixed file sizes in a two-link model. First, we derive the optimal file delivery scheduling without changes in the delivery order at the intermediate node. We then discuss the difficulty to obtain the optimal scheduling with delivery order change at the intermediate node. We also examine the conditions of reducing the total service latency and an upper bound of the latency improvement rate. Finally, we analyze the file delivery scheduling in a general network environment and show that practical consideration of the delivery order change at the intermediate node is not necessary.

This paper improves the conventional scheme of contents sharing in unstructured P2P networks, where each of the peers and content cache routers keeps contents cache as well as query transmission records, which are used to guide content searching queries and reduce the number of the queries without losing contents discovery rates. In this paper, the decision whether a content item is cached or not on the router is executed as a part of the algorithm running in the contents sharing system according to the content item's popularity and the degree of the router as a network node, in order to reduce the frequency of contents loss caused by the displacement or overwriting of caches in the routers. The efficiency of the improvement is discussed using the results of computer simulations.

In this paper, we propose dynamic control of output timing of fragrance in a networked virtual environment to improve Quality of Experience (QoE). The control changes the output timing of fragrance dynamically according to the movement speed and direction of an object which is a fragrance source. We implement the control in a remote ikebana system using olfactory and haptic media and investigate the effect of the control by QoE assessment. As a result, we demonstrate that Mean Opinion Score (MOS) in the case where the control is used is high and does not largely depend on the average movement speed and movement direction of a flower, which is a fragrance source.

In this paper, we handle an air hockey game which two users play with haptic interface devices as an example of networked real-time games. In order to improve the interactivity of the air hockey game, we propose the adaptive Δ (delta)-causality control scheme with prediction, which keeps the consistency and causality high and predicts positional information after a constant time. In QoE (Quality of Experience) assessment, we assess the output quality and interactivity of local mallet, output quality of opponent's mallet, output quality and interactivity of puck, and comprehensive quality. As a result, we illustrate that the proposed scheme is effective and there exists the optimal value of the prediction time.

In this paper, we investigate the influence of network delay on the quality of experience (QoE) for a tele-operation system with 3D (i.e., stereoscopic) video and haptic media. We assess the video output quality, operability of the haptic interface device, inter-stream synchronization quality (or inter activity), and comprehensive quality as QoE. We also evaluate the application-level quality of service (QoS). By multiple regression analysis, we demonstrate that it is possible to estimate QoE parameters from QoS parameters with a high degree of accuracy.

In this paper, we deal with a remote haptic instruction system in which a teacher teaches a student how to write characters by using haptic interface devices. We have two cases in the system. In one case, a pen is attached to only the student terminal, and video is transmitted from the student terminal to the teacher terminal. In the other case, a pen is attached to each of the two terminals, and video is transmitted bi-directionally between the terminals. In both cases, we make a comparison between two-way transmission and one-way transmission of the sense of force by subjective assessment.

By subjective assessment, this paper investigates the effects of group (or inter-destination) synchronization control in networked virtual environments where users have a conversation with each other by using avatars constructed by computer graphics (CG) and live voices. Assessment results show that the fairness among the users can be maintained high under the group synchronization control in networked competitive work. We also demonstrate that the synchronization quality of networked collaborative work can be improved under the group synchronization control. In addition, we make an experiment in which we use videos instead of avatars, and we examine the difference between results of the avatar case and those of the video case.

In this paper, we deal with a remote haptic calligraphy system in which a teacher instructs multiple students at remote location show to write characters while conveying the sense of force by multicast communications. We also propose an error control scheme which transmits important media units (MUs) multiple times which include the positional information in the case where the speed of the teacher's brush stroke is faster than a threshold value by adding the MUs to the succeeding MUs as well as transmitting them independently. By experiment, we demonstrate that the proposed scheme can keep the media output quality high at the expense of slight increase of the traffic amount.

In this paper we propose a new scheduler. Deadline fair sharing (DFS), which consists of link scheduling and dropping mechanisms to provide absolute delay and loss guarantees in DiffServ networks. The scheduling mechanism uses dynamic weight associated with each class to schedule the packets and to make a dropping decision when an absolute delay guarantee violation occurs. The dropping mechanism drops packets and detects the onset of an early violation for absolute loss guarantee. When an early violation for the absolute loss guarantee of a class is detected, the scheduling mechanism gives that class more priority for transmitting its packets to prevent that violation. The simulation results show that the proposed scheduler can provide a wide range of absolute loss and delay bounds under various traffic load conditions without controlling the traffic.

This paper describes a new distributed control method for the connection-oriented-type packet network, where a number of connections must be established at the same time, and each connection has different characteristics, for example, different allowable delays or different traffic densities. In the described method, routing and priority control based on game theory are applied; two players, a connection player and a network player play the game based on the mini-max principle. The computer simulation shows that this method can decrease the number of packet losses caused by the transmission delay.