Kyoko Yamori

Relation between willingness to pay and guaranteed minimum bandwidth in multiple-priority service

In recent years, the necessity of quality guaranteed services is increasing in the Internet. The differentiated services, which have multiple classes using priority control, are being introduced. Various issues need to be addressed when providing differentiated services, such as what sort of quality should be guaranteed, and what kind of pricing should be made for the service. We address this problem by making it easier for test subjects to visualize the quality of service available with a minimum guaranteed bandwidth when evaluating the willingness to pay. In this paper, the quantitative relation between the guaranteed minimum bandwidth and the willingness to pay is shown by the subjective experiment of streaming contents and by the questionnaire survey of the waiting time for download.

A service quality coordination model bridging QoS and QoE

Both of Quality of Service (QoS) and Quality of Experience (QoE) are defined to specify the degree of service quality. Although they are dealt with in different layers in multi-layered models, collaboration of these is necessary to improve the user satisfaction for telecommunication services. In this paper, after sorting out the concepts and specification of QoS and QoE, a service quality coordination model combining these is proposed. The model is applied to a video-sharing service and its coordination model is derived based on subjective experiments. The structural equation modeling is used to compute the user satisfaction from QoS and QoE.

A practical dimensioning method for ATM systems

In this paper, a simplified practical method for dimensioning asynchronous transfer mode (ATM) systems is proposed. Packet switching services are classified into two categories: connection-oriented packet switching (COPS) with quality of service (QoS) guaranteed and connection-less packet switching (CLPS) on a best effort basis. A new control scheme is proposed for maintaining the cell-level QoS requirement for the COPS even in overload conditions. A dimensioning method is also proposed for the system where the COPS is served with nonpreemptive priority over the CLPS. The methods proposed are expected to contribute to the realization of robust and economical ATM systems.

Quality of experience modeling with psychological effect for interactive Web services

Notion of the user-centered design (UCD) is requisite to improve user satisfaction. Matching the concept of UCD, Quality of Experience (QoE) is expected to become a paradigm shift from the existing operator-initiative network services. There are, however, several difficulties to realize practical communication services based on QoE. One difficulty is how to bridge QoE and Quality of Service (QoS) parameters relevant to system performance. Moreover, since QoE is based on the end-user subjective evaluation, flexible modeling corresponding to the end-user psychological status is needed. In this paper, an interactive Web service is considered and a QoE model with end-user psychological effect is derived by use of the Weber-Fechner law. Data of QoE and QoS parameter are collected through experiments and the mapping functions between QoE and QoS are estimated from the data.

Price Optimization of Contents Delivery Systems with Priority

For data delivery systems such as video-on-demand service, an optimum design is presented to maximize the revenue of the system with priority classes. The willingness-to-pay (WTP) is introduced for a measure of utility (price), and the optimum design is discussed to maximize the revenue. For the system with two priority classes, the optimum condition is given in terms of the traffic load, waiting time for service and pricing for the priority and non-priority classes. In this paper, we use the WTP as the measure of pricing. And we would like to examine the optimum design to propose the optimum pricing methods for timebase and flat-base. In this paper, using the WTP, the utility (price) of the data delivery system has been quantified, and the optimum condition to maximize the revenue of the system has been analyzed. From the numerical examples, the optimum condition for the service grade (waiting time for service) and pricing for priority and non-priority classes has been discussed.

Distributed association control considering user utility and user guidance in IEEE802.11 networks

Public WLANs based on IEEE802.11 standard are now widely deployed. In an environment offering several APs (Access Points), a UTE (User Terminal Equipment) needs to choose which AP to associate with. Conventionally, the UTE associates with the AP with the strongest RSSI (Received Signal Strength Indicator). This simple approach, however, can degrade the efficiency of network utilization since the UTE is likely choose a heavily loaded AP, even though choosing a more lightly loaded AP would be more effective. So far, some AP association schemes have been proposed. To the best of our knowledge, however, these existing schemes do not take into account of individual difference among UTEs in terms of user utility, physical data rate, traffic characteristics such as traffic demand and frame length. In this paper, we propose a distributed user association control scheme that does considering such UTE characteristics. The proposed scheme needs to estimate uplink and downlink throughput, so that we introduce a throughput estimation method that considers UTE diversities. Through numerical simulations, we confirm that our distributed control scheme can improve user utility and fairness.

Content Clustering Based on Users’ Subjective Evaluation

Users demand of the quality of streaming service depends on intrinsic characteristics of the content. Various items can be considered as a characteristic. These characteristics are rated on a scale of intensity from 1 to 5. In this paper it is denoted that intensity based on sound or image quality is a characteristic of the content. A subjective evaluation experiment was carried out on several genres of content. The relation between content characteristics and content types is shown by using, principal component analysis. Then, based on the image quality and sound quality, the content is divided into several groups using cluster analysis

Measure of user behaviour before and during disaster congestion

Network congestion during large scale disasters seems inevitable. Sudden influx of traffic caused by users calling their loved ones, coupled with the possibility that many base stations and routers in the area are damaged by the disaster; leads to resource shortage which causes congestion, which in turn causes many users becoming disgruntled and their quality of experience dropping. If a study can be made on predicting user behaviour, based on usual user habits and way of acting immediately after a disaster, then the network provider can regulate traffic accordingly or take precautions in areas within disaster zones.

Integration of time-dependent pricing with transmission rate control for flattening out peak-time demand

This paper studies the impact of transmission rate control and pricing on the congestion management practices on bottleneck links of Internet service provider (ISP). QoS negotiation between ISP and users is conducted by letting users specify their minimum and maximum transmission rate required. Each link tentatively allocates the maximum transmission rates to the traffics that are going to cross it. When the available capacity becomes not enough to satisfy the maximum transmission rate requirements of all on-going users, ISP reduces the allocated transmission rates of connections one by one according to their priorities. When the transmission rate allocated to every user decreases to the minimum transmission rate required, ISP then sends peak-time notification to all on-going users and employs pricing as an incentive mechanism to encourage voluntary disconnections (soft delay). Prices adopted during congestion is completely time-dependent and varies according to the real-time network congestion level. Specifically, the price of each time slot is obtained by solving a maximization problem of network utilization. If the available capacity is still not enough to satisfy the minimum transmission rate requirements of all on-going users, ISP forcibly delays connections one by one also on a priority basis (hard delay). Simulation results show that the proposed approach can significantly shift demand from peak time to off-peak time. When baseline demand is set to be 25% over the capacity of the link (i.e., peak time), 28.2% users voluntarily delay their connections for 0.23 hour under the price incentives, and only 0.84% users are forcibly delayed by ISP.

Analysis of willingness to pay in guaranteed multiple-priority service

Differentiated services, which have multiple classes using priority control have recently been introduced. Various issues need to be addressed when providing multiple-priority, such as what sort of quality should be guaranteed, and what kind of pricing should be applied to the service. In this paper, the quantitative relation between the guaranteed bandwidth and willingness to pay (WTP) is shown by the questionnaire survey. We also did a factor analysis using regression and quantification method I to identify the factors that affect WTP. We identified that the main factors that affect the potential WTP are the number of usage days per week and over-midnight usage. And we also showed that the main factors that affect the sensitivity of the increase in WTP are the bandwidth at response time and the usage duration per day.