A konferencia előadás címe: An effcient method to solve a two-server heterogeneous retrial queue with threshold policy
A cikk címe: Modeling the Performance and the Energy Usage of Wireless Sensor Networks by Retrial Queueing Systems
This paper deals with wireless transmission problems in sensor networks. In order to study the performance measures and characteristics, a finite source retrial queueing model is introduced. Two classes of sensors are considered: "time driven" sensors for normal requests and "event driven" sensors with high priority for special, eg. emergency requests. The main goal is to investigate the relationship between the performance and the energy usage of the sensor network. Two operations are compared. In the first case only the event driven requests can initiate reaching the radio transmission (RF) unit. Time driven requests have to wait for a listening period of RF unit. In the second case the time driven requests also are able to access the sleeping RF unit, which will go to power save (sleeping) state immediately after the job is served. The steady-state performance measures and probabilities are given by the help of the MOSEL-2 tool.
Benyújtotottam a Modeling the RF communication in sensor networks by using finite-source retrial queueing system című cikket a Scientific Bulletin of the "Politehnica" University of Timisoara folyóiratba.
In this paper we study the radio frequency (RF) transmission in wireless sensor networks. A new finite source queueing model is introduced in order to calculate the most important system performance characteristics (e.g. mean waiting time, mean number of requests waiting for transmission). The sensors form the "sources" and the RF unit represents the "service station" of the queueing model. The sensors are classified according to their working purposes: The first class is the "Emergency" class, which is responsible to notify special emergency situations (e.g. fire alarms). The second class is the "Standard" class, which performs the measurement of standard environmental data (e.g. humidity). The RF unit may enter into energy saving (or "sleeping") working mode in order to spare energy and have longer battery life. The RF communication is stopped in the sleeping mode. Concerning the "wake up" mechanism from the energy saving mode we differentiate two cases and create two models to compare their steady-state system performance measures: In the first model the RF transmission possibility will be available randomly for the sensor nodes (Non Controlled case). In the second model the RF transmission requests coming from the emergency class, will access the wireless channel immediately (Controlled case).
A cikk címe: Modeling the RF communication in sensor networks by using finite-source retrial queueing system
In this paper we study the radio frequency (RF) transmission in wireless sensor networks. A new finite source retrial queueing model is introduced in order to calculate the most important system performance characteristics (e.g. mean waiting time, mean number of requests waiting for transmission). The sensors form the "sources" and the RF unit represents the "service station" of the queueing model. The sensors are classified according to their working purposes: The first class is the "Emergency" class, which is responsible to notify special emergency situations (e.g. fire alarms). The second class is the "Standard" class, which performs the measurement of standard environmental data (e.g. humidity, temperature). The RF unit may enter into energy saving (or "sleeping") working mode in order to spare energy and have longer battery life. The RF communication is stopped in the sleeping mode. Concerning the "wake up" mechanism from the energy saving mode we differentiate two cases and create two models to compare their steady-state system performance measures: In the first model the RF transmission possibility will be available randomly for the sensor nodes (Non Controlled case). In the second model the RF transmission requests coming from the emergency class, will access the wireless channel immediately (Controlled case).
Az előadás címe: Using PRISM to model spectrum renting in mobile cellular networks
We report on the use of high performance computing in order to analyze with the probabilistic model checker PRISM mobile cellular networks, in particular the system described in the paper "A New Finite-Source Queueing Model for Mobile Cellular Networks Applying Spectrum Renting" by Tien v. Do et al [1]. That paper proposes a new finite-source retrial queueing model with the finite number of sources to investigate the performance measures of the system. In the original paper the numerical results was produced using MOSEL-2 softver tool. Our results show that the model can be also appropriately described and analyzed in PRISM.
Benyújtotottam a "A Finite-Source Queuing Model for Spectrum Renting in Mobile Cellular Networks" című cikket az ELEKTRO2014 Szlovákiában megrendezésre kerülő konferenciára.
Nowadays, spectrum renting is a frequently investigated research topic with the aim of improving the efficiency of spectrum usage in mobile cellular networks. In this paper, we propose a finite-source queuing model, in which service providers may rent each other’s unutilized frequency bands. Our model contains two source pools: one for subscribers generating fresh calls in the investigated mobile cell, and another for modeling handover calls. The model considers the traveling of subscribers over the borders of the investigated mobile cell, too. Moreover, we take into account the retrial phenomenon caused by the impatience of subscribers.
Benyújtotottuk a "Performance Modeling of Finite-Source Cognitive Radio Network" című cikket az ASMTA-2014 konferenciára.
This paper deals with the topic of radio frequency licensing. The performance can be increased by the idea of the cognitive radio. Licensed users (Primary Users - PUs) and normal users (Secondary Users - SUs) are considered. The main idea is, that the SUs are able to access to the available non-licensed radio frequencies. Queueing theory can be successfully applied to analyze this problem. In this paper a finite source queueing model is introduced with two (non independent) frequency bands. A service unit with a priority queue and a service unit with an orbit are assigned to the PUs and SUs, respectively. The users are classified into two classes: the PUs have got a licensed frequency. The SUs have got a frequency band too, but it suffers from the overloading. We perform numerical calculations to investigate the behaviour the cognitive radio. The main focus is to get an optimal number of SUs, where the gained utilization (when switching to the cognitive radio) has a maximum value.
Elfogadták a "A Finite-Source Queuing Model for Spectrum Renting in Mobile Cellular Networks" című cikket az ELEKTRO2014 konferenciára.
Nowadays, spectrum renting is a frequently investigated research topic with the aim of improving the efficiency of spectrum usage in mobile cellular networks. In this paper, we propose a finite-source queuing model, in which service providers may rent each other’s unutilized frequency bands. Our model contains two source pools: one for subscribers generating fresh calls in the investigated mobile cell, and another for modeling handover calls. The model considers the traveling of subscribers over the borders of the investigated mobile cell, too. Moreover, we take into account the retrial phenomenon caused by the impatience of subscribers.
Elfogadták a "Probabilistic Model Checking on HPC Systems for the Performance Analysis of Mobile Networks" című cikket az Annales Mathematicae et Informaticae folyóiratba.
We report on the use of HPC resources for the performance analysis of the mobile cellular network model described in \enquote{A New Finite-Source Queueing Model for Mobile Cellular Networks Applying Spectrum Renting} by Tien Van Do {\it et al}. That paper proposed a new finite-source retrial queueing model with spectrum renting that was analyzed with the MOSEL-2 tool. Our results show how this model can be also appropriately described and analyzed with the probabilistic model checker PRISM, although at some cost considering the formulation of the model; in particular, we are able to accurately reproduce most of the analytical results presented in that paper and thus increase the confidence in the previously presented results. However, we also outline some discrepancies which may hint to deficiencies of the original analysis. Moreover, by applying a parallel computing framework developed for this purpose, we are able to considerably speed up studies performed with the PRISM tool. The investigations are illustrated by figures and conclusions are drawn.
A Hírközlési és Informatikai Tudományos Egyesület az Infocommunications Journal 2013/2. évi számában megjelent „The effect of RF unit breakdowns in sensor communication networks” cikkéért az Egyesület Pollák-Virág díj kitüntetésben részesíet.
Az előadás címe: A new nite-source queueing model for Spectrum Renting and handover calls in Mobile Cellular Networks
Az előadás címe: A queueing model for Spectrum Renting and handover calls in Mobile Cellular Networks
Following the common practice applied in the theory of retrial queues for performance evaluation, this paper proposes a finite-source retrial queueing model to consider spectrum renting and handover calls in mobile cellular networks, in which service providers may rent each other’s unutilized frequency bands. The model incorporates switching servers on and off in groups, considers new and handover calls. We present a novel way to take into account the blocking probability of new and handover calls.
Elfogadták a "Modeling a QoS classified communication in a multiuser Wi-Fi environment" című cikket az Infocommunication folyóiratba.
The aim of the present paper is to propose a finite source queueing model in order to include the random backoff feature of the wireless communication. Two classes of sources (high priority and low priority traffic) are included. The random backoff feature is implemented by using retrial queues for each traffic class. Supposing exponentially distributed interevent times the MOSEL software tool is used to develop the special software to calculate the most important steady-state performance characteristics of the system, such as utilizations, mean orbit sizes, mean waiting times, that is mean time spent in the orbit. It is showed how the retrial discipline effects the mean waiting times (compared to the FIFO discipline): not only the values, but also the form of the curve is quite different in the case of packet reordering.