Tuan Phung-Duc

Tuan Phung-Duc
University of Tsukuba · College of Policy and Planning Sciences

Doctor of Informatics (Kyoto University)

About

137
Publications
19,447
Reads
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1,150
Citations
Introduction
Tuan Phung-Duc is an Associate Professor at University of Tsukuba. He received a Ph.D. in Informatics from Kyoto University in 2011. He is currently on the Editorial Board of some International Journals and was a Guest Editor of four Special Issues of Annals of Operations Research. Dr. Phung-Duc received the Research Encourage Award from The Operations Research Society of Japan in 2013. His research interests include Stochastic Modelling, Performance Analysis and Stochastic Models.
Additional affiliations
January 2019 - present
University of Tsukuba
Position
  • Professor (Associate)
April 2016 - December 2018
University of Tsukuba
Position
  • Professor (Assistant)
April 2012 - March 2016
Tokyo Institute of Technology
Position
  • Professor (Assistant)
Education
April 2008 - March 2011
Kyoto University
Field of study
  • Graduate School of Informatics

Publications

Publications (137)
Article
Full-text available
This paper considers a double-ended queueing system in which both the supply and demand sides adopt strategic behaviors in observable and unobservable cases. Systems with only one type of strategic agents are common in literature. Agents in these systems follow the crowd and form a common strategy adopted by all at the evolutionary endpoint, which...
Article
Full-text available
This paper considers a modified Erlang loss system for cognitive wireless networks and related applications. A primary user has pre-emptive priority over secondary users, and the primary customer is lost if upon arrival all the channels are used by other primary users. Secondary users cognitively use idle channels, and they can stay (either in an i...
Chapter
Full-text available
This paper considers a retrial tandem queue with single orbit, Poisson arrivals of incoming calls and without intermediate buffer. The first server provides services for incoming calls for an arbitrary random time, while the second server does for an exponentially distributed random time. Blocked customers at either the first server or the second s...
Article
Full-text available
In this study, the existing game theoretical framework is extended to strategic queuing in search of solutions for a two-population game in observable double-ended queuing systems with zero matching times. We show that multiple Nash equilibria and one unique subgame perfect Nash equilibrium exist in this game.
Article
Full-text available
This paper considers an observable double-ended queueing system of passengers and taxis, where matching times follow an exponential distribution. We assume that passengers are strategic and decide to join the queue only if their expected utility is nonnegative. We show that the strategy of passengers is represented by a unique vector of thresholds...
Article
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This paper deals with an observable batch service queueing system in which customers rationally choose whether to form a batch with another customer or not, in addition to deciding whether or not to join the queue. When choosing whether to form a batch, a customer in an incomplete batch decides on an optimal waiting time for the next customer to ar...
Article
Full-text available
This paper studies a single-server retrial queue with two types of calls (incoming and outgoing calls). Incoming calls arrive at the server according to a renewal process, and outgoing calls of N−1 (N≥2) categories occur according to N−1 independent Poisson processes. Upon arrival, if the server is occupied, an incoming call joins a virtual infinit...
Article
Full-text available
This paper considers queueing models for cognitive radio networks that account for the sensing time of secondary users (SUs). In cognitive radio networks, secondary users are allowed to opportunistically use idle channels originally allocated to primary users (PUs). To this end, SUs must sense the state of the channels before transmission. After se...
Article
Full-text available
In this paper, we propose Car/Ride-Share (CRS), which is a new transportation service aiming at reducing the uneven distribution of cars in traditional carsharing service. The proposed service might be used as an alternative for buses in the case of congestion. In our model a car will depart from a bus stop at a university to a train station if the...
Article
Full-text available
Mobile Edge Computing architecture is one of the most promising architectures that can satisfy different quality of Services required by various applications. In this paper, we model mobile edge computing architecture with queue-length thresholds at user equipments and edges to determine whether the task is offloaded or not in federated cloud and e...
Chapter
Full-text available
In this paper, we consider an asymptotic analysis for the stationary queue length of a tandem queueing system with one orbit, Poisson arrival process of incoming calls and two sequentially connected servers. Under the condition that the average delay time of calls in the orbit is extremely large, we obtain the asymptotic probability distribution of...
Chapter
NFV (Network Functions Virtualization) technology widely deployed in recent cloud computing is essential to provide network services. NFV is useful for saving operational cost because VNFs (Virtualized Network Functions) are created dynamically by scaling in/out virtual machines. On the other hand, utilizing existing computing resources, which are...
Chapter
We employ Mixture Density Networks (MDNs) as a general approach for estimation of customer waiting times in queueing systems based on system states that customers observe upon their arrival. We generate a large amount of data by using discrete-event simulation. Part of the generated dataset is used to train the model, and we utilize the whole datas...
Chapter
Full-text available
In this research, we discuss Car/Ride-Share (CRS), which is a novel concept of Demand Responsive Transportation (DRT) aiming at reducing the uneven distribution of cars in traditional carsharing service and the congestion of cars and people. We model a scenario where CRS service is introduced between a spot (e.g., university, company, etc.) and its...
Chapter
Full-text available
In this paper, we consider an infinite server queue with batch service. Although many studies on queues with finite number of servers and batch service have been conducted, there are only a few research related to the infinite server queue with batch service and they only consider the moments of the queue length. We present the derivation of the st...
Chapter
Full-text available
In this paper, we present a diffusion limit for the time-dependent distribution of the number of customers in the orbit for a tandem queueing system with one orbit, Poisson arrival process of incoming calls and two sequentially connected servers using a characteristic function approach. Under the condition that the mean time of a customer in the or...
Article
Full-text available
Motivated by the trade-off issue between delay performance and energy consumption in modern computer and communication systems, we consider a single-server queue with phase-type service requirements and with the following two special features: Firstly, the service speed is a piecewise constant function of the workload. Secondly, the server switches...
Chapter
In this paper, we consider a single-server retrial queue with unreliable server and two-way communication. Inbound calls arrive according to a Poisson process. If the server is busy upon arrival, an incoming call joins the orbit and retries to occupy the server after some exponentially distributed time. Service durations of incoming calls follow th...
Chapter
This paper considers a priority multi-server retrial queue with two classes of customers. Primary customers have preemptive priority over secondary users. The dynamics of primary customers is the same as that of an Erlang loss system with Poisson input and exponential service time distribution. Secondary users can cognitively use the channels when...
Preprint
Full-text available
This paper considers a modified Erlang loss system for cognitive wireless networks and related applications. A primary user has preemptive priority over secondary users and the primary customer is lost if upon arrival all the channels are used by other primary users. Secondary users cognitively use idle channels and they can wait at an infinite buf...
Book
This book constitutes the refereed proceedings of the 17th European Workshop on Computer Performance Engineering, EPEW 2021, and the 26th International Conference, on Analytical and Stochastic Modelling Techniques and Applications, ASMTA 2021, held in December 2021. The conference was held virtually due to COVID 19 pandemic. The 29 papers presented...
Article
Full-text available
In the paper, we consider a multi-server retrial queueing system with setup time which is motivated by applications in power-saving data centers with the ON-OFF policy, where an idle server is immediately turned off and an off server is set up upon arrival of a customer. Customers that find all the servers busy join the orbit and retry for service...
Chapter
Full-text available
The paper deals with a queueing model, arising in the cognitive radio networks, with one server and two types of users - primary and secondary. The primary users arrive according to a Poisson flow and have preemptive priority over the secondary users, which form a quasi-random input of demands. Each secondary user upon its arrival has to join the o...
Chapter
Sharing services such as carsharing and ridesharing have been widely spreading in our modern society. This paper considers “Car Ride Sharing (CRS)” which is a mixed model of carsharing and ridesharing. CRS is a new means of transportation which shares “car” and “ride” simultaneously and it is expected to reduce the redistribution cost of cars. We i...
Chapter
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This paper considers the performance of a collision channel where the transmissions of packets are split in two phases. Arriving packets who see the transmission channel idle, occupy it immediately. Arriving packets cannot detect ongoing transmissions during the first phase of transmission. Hence, if the first part or phase of the packet is being t...
Chapter
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We propose an analytical method for an M/M/1 vacation queue with workload dependent service rates. We obtain the distribution of the workload in the system, and consider a power-saving and performance trade-off problem. Numerical experiments reveal that square root service rate function has lower cost than that of linear and quadratic service funct...
Article
Full-text available
This paper considers a finite capacity multiserver queue for performance modeling of data centers. One of the most important issues in data centers is to save energy of servers. To this end, a natural policy is to turn off a server immediately once it has no job to process. In this policy, which is called ON–OFF policy, the server must be setup upo...
Article
Full-text available
In this paper we deal with a single-server, finite-source retrial queue where the server not only accepts incoming calls but after some exponentially distributed idle time makes outgoing calls. The service times of incoming and outgoing calls follow two distinct arbitrary distributions. The outgoing calls are directed not to the customers in the sy...
Chapter
Full-text available
Queues with setup time are extensively studied because they have application in performance evaluation of power-saving data centers. In data centers, there are a huge number of servers which consume a large amount of energy. In the current technology, an idle server still consumes about 60% of the energy when it is busy. Thus, a simple way to save...
Article
In this paper, we consider an MX/M/1/GSET-VARI queue, which is a single server queue with a variable service speed, batch arrivals and general setup times. The service speed of the server is proportional to the number of jobs in the system. Our model is motivated by power-aware servers in data centers where dynamic scaling techniques are used. In t...
Book
This book constitutes the refereed proceedings of the 16th European Workshop on Computer Performance Engineering, EPEW 2019, held in Milan, Italy, in November 2019. The 10 papers presented in this volume together with one invited talk were carefully reviewed and selected from 13 submissions. The papers presented at the workshop reflect the diversit...
Chapter
In this paper, we consider the multiclass M/M/1/1 retrial queueing system. Customers of each class arrive from outside the system according to a Poisson process. The service times of customers are assumed to be exponentially distributed with the parameter corresponding to the type of the customer. If the server is busy incoming customers join the o...
Chapter
In this paper, we consider a multiserver retrial queue with two-way communication. Incoming calls arrive according to the stationary Poisson process and occupy the servers. Durations of incoming calls have an exponential distribution. If all the servers are busy upon arrival, the incoming call joins the orbit. The time spent by the call in the orbi...
Chapter
In this paper, we consider a retrial queue with batch Poisson input process, arbitrarily distributed service times and arbitrarily distributed number of calls in the batch. Upon arrival, a call from the batch occupies the server if it is idle. The other calls from the batch join the orbit. If the server is busy, all calls from the batch go to the o...
Chapter
The main purpose of present paper is to study the busy period in one single-server, finite-source retrial queue with outgoing calls. The specific feature of this system is that the outgoing calls do not affect the customers in the system. This allows the model to be considered as a queue with two types of customers. The service times of incoming an...
Chapter
In this paper, we consider a single server queueing model \(M^{[n]}|GI|GI|1|L\) with Batch Poisson input flow. Upon arrival, an incoming call from the batch occupies the server, if the server is idle. Other calls from the batch join the orbit and try to occupy the server after an exponentially distributed time. If the server is busy all incoming ca...
Chapter
This paper considers a cognitive radio network system which has two classes of users that we call Primary Users and Secondary Users. We model this system using a single server retrial queueing model. In the conventional retrial queue, if a customer cannot find an idle channel, he joins the orbit and retries to occupy a channel. The new feature of o...
Chapter
Full-text available
In modern data centers, the trade-off between processing speed and energy consumption is an important issue. Motivated by this, we consider a queueing system in which the service speed is a function of the workload, and in which the server switches off when the system becomes empty, only to be activated again when the workload reaches a certain thr...
Chapter
Full-text available
Nowadays, Parcel Delivery Service (PDS) has become popular due to the popularization of Electric Commerce (EC). The redelivery problem has also become serious due to the absence of receivers and the courier must deliver again at a later time. The increase in the number of redeliveries causes social losses such as extra workload of delivery, carbon...
Preprint
Full-text available
Retrial phenomenon naturally arises in various systems such as call centers, cellular networks and random access protocols in local area networks. This paper gives a comprehensive survey on theory and applications of retrial queues in these systems. We investigate the state of the art of the theoretical researches including exact solutions, stabili...
Article
Full-text available
We consider a retrial queueing model for random access protocols arising in local area networks such as carrier sense multiple access networks. In our model, one channel is shared among multiple nodes. Each node accesses the channel according to a Poison process and the holding time of the channel is exponentially distributed. Blocked users join th...
Article
In this paper, we consider an MMPP/M/1/1 retrial queue where incoming fresh calls arrive at the server according to a Markov modulated Poisson process (MMPP). Upon arrival, an incoming call either occupies the server if it is idle or joins a virtual waiting room called orbit if the server is busy. From the orbit, incoming calls retry to occupy the...
Article
This paper considers the stationary queue length distribution of a Markov-modulated MX/M/∞queue with binomial catastrophes. When a binomial catastrophe occurs, each customer is either removed with a probability or is retained with the complementary probability. We focus on our model under a heavy traffic regime because its exact analysis is difficu...
Book
This book constitutes the proceedings of the 14th International Conference on Queueing Theory and Network Applications, QTNA 2019, held in Ghent, Belgium, in August 2019. The 23 full papers included in this volume were carefully reviewed and selected from 49 initial submissions. The papers are organized in topical sections on Retrial Queues; Contro...
Article
This paper considers the stationary queue length distribution of a Markov-modulated MX/M/∞ queue with binomial catastrophes. Binomial catastrophes occur according to a Poisson process, and each customer is removed with a probability and retained with the complementary probability upon the arrival of a binomial catastrophe. We focus on our model und...
Conference Paper
This paper considers a multiserver loss system with servers-orbit interaction and feedbacks motivated from call centers. Incoming calls that are blocked upon arrival join an orbit from which they independently retry after some random time. In addition, idle servers make outgoing calls to the customers either in the orbit or outside. We assume that...
Conference Paper
Full-text available
We analyze a novel Markovian single-server system with two queues for call-back option and feedback. If upon arrival the server is busy, the job registers to be called back later by the server. A job that completes its service may request another round of service. Registered jobs and feedback jobs are said to be in two separated queues from which t...
Chapter
In this paper, we apply a regenerative approach to reprove some recent steady-state results [1, 8, 9] for an orbit-queue (also known as retrial queue with a constant retrial rate) with outgoing calls. Stability conditions are discussed as well. Moreover, some generalizations of the model are also considered.
Article
Full-text available
We calculate asymptotics of the distribution of the number of customers in orbit in a two-class priority retrial $M/G/1$-type queueing model. In this model, priority customers wait in line while non-priority customers join an orbit and retry later. Although the generating function and moments of the number of customers in orbit has been analyzed be...
Conference Paper
Full-text available
How Profitable is the period of idleness of a server in a network? Queueing theory aims to answer to such a question amongst others. We restrict ourself to the problem of profitability of idleness of the server from the point of view of two-way communication in call centers in relation with retrial queueing models. This problem has been investigate...
Conference Paper
Full-text available
The paper deals with two-way communication M/M/1/1 retrial queue where the server during its idle time makes outgoing calls of two types - to the customers in orbit and to the customers outside it. Durations of these calls follow two distinct exponential distributions. After completion of the outgoing call to a customer from orbit, this customer wi...
Conference Paper
In this paper, we consider an MMPP/M/1/1 retrial queue where incoming fresh calls arrive at the server according to a Markov modulated Poisson process. Upon arrival, an incoming call either occupies the server if it is idle or joins an orbit if the server is busy. From the orbit, an incoming call retries to occupy the server and behaves the same as...
Article
Full-text available
In this paper, we consider an M(Formula presented.)/M/1/SET-VARI queue which has batch arrivals, variable service speed and setup time. Our model is motivated by power-aware servers in data centers where dynamic scaling techniques are used. The service speed of the server is proportional to the number of jobs in the system. The contribution of our...
Article
Full-text available
This paper considers a multiserver retrial queue with setup time which is motivated from application in data centers with the ON-OFF policy, where an idle server is immediately turned off. The ON-OFF policy is designed to save energy consumption of idle servers because an idle server still consumes about 60% of its peak consumption processing jobs....
Conference Paper
We consider in this paper retrial queue with one server that serves a finite number of customers, each one producing a Poisson flow of incoming calls. In addition, after some exponentially distributed idle time the server makes outgoing calls of two types - to the customers in orbit and to the customers outside it. The outgoing calls of both types...