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001-es BibID:	BIBFORM077596
035-os BibID:	(Scopus)85061753742
Első szerző:	Nemouchi, Hamza
Cím:	Performance Simulation of Finite-Source Cognitive Radio Networks with Servers Subjects to Breakdowns and Repairs / H. Nemouchi, J. Sztrik
Dátum:	2019
ISSN:	1072-3374 1573-8795
Megjegyzések:	The present paper deals with the performance evaluation of a cognitive radio network with the help of a queueing model. The queueing system contains two interconnected, not independent sub-systems. The first part is for the requests of the Primary Units (PU). The number of sources is finite, and each source generates high priority requests after a exponentially distributed time. The requests are sent to a single server unit or Primary Channel Service (PCS) with a preemptive priority queue. The service times are assumed to be exponentially distributed. The second sub-system is for the requests of the Secondary Units (SU), which is finite sources system too; the inter-request times and service times of the single server unit or Secondary system Channel Service (SCS) are assumed to be exponentially distributed, respectively. A generated high priority packet goes to the primary service unit. If the unit is idle, the service of the packet begins immediately. If the server is busy with a high priority request, the packet joins the preemptive priority queue. When the unit is engaged with a request from SUs, the service is interrupted and the interrupted low priority task is sent back to the SCS. Depending on the state of the secondary channel, the interrupted job is directed to either the server or the orbit. In case the requests from SUs find the SCS idle, the service starts, and if the SCS is busy, the packet looks for the PCS. In the case of an idle PCS, the service of the low-priority packet begins at the high-priority channel (PCS). If the PCS is busy, the packet goes to the orbit. From the orbit it retries to be served after an exponentially distributed time. The novelty of our investigation is that each server is subject to random breakdowns, in which case the interrupted request is sent to the queue or orbit, respectively. The operating and repair times of the servers are assumed to be generally distributed. Finally, all the random times included in the model construction are assumed to be independent of each other. The main aim of the paper is to analyze the effect of the nonreliability of the servers on the mean and variance of the response time for the SUs by using simulation.
Tárgyszavak:	Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Journal of Mathematical Sciences. - 237 : 5 (2019), p. 702-711. -
További szerzők:	Sztrik János (1953-) (informatikus, matematikus)
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat Szerző által megadott URL
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001-es BibID:	BIBFORM084211
035-os BibID:	(Scopus)85082570473
Első szerző:	Tóth Ádám (mérnökinformatikus)
Cím:	The Simulation of Finite-Source Retrial Queueing Systems with Collisions and Blocking / Á. Tóth, T. Bérczes, J. Sztrik, A. Kuki, W. Schreiner
Dátum:	2020
ISSN:	1072-3374 1573-8795
Megjegyzések:	This paper investigates, using a simulation program, a retrial queuing system with a single server which is subject to random breakdowns. The number of sources of calls is finite, and collisions can take place. We assume that the failure of the server blocks the system's operation such that newly arriving customers cannot enter the system, contrary to an earlier paper where the failure does not affect the arrivals. All the random variables included in the model construction are assumed to be independent of each other, and all times are exponentially distributed except for the service time, which is gamma distributed. The novelty of this analysis is the inspection of the blocking effect on the performance measures using different distributions. Various figures represent the impact of the squared coefficient of the variation of the service time on the main performance measures such as the mean and variance of the number of customers in the system, the mean and variance of the response time, the mean and variance of the time a customer spends in the service, and the mean and variance of the sojourn time in the orbit.
Tárgyszavak:	Műszaki tudományok Informatikai tudományok konferenciacikk folyóiratcikk
Megjelenés:	Journal of Mathematical Sciences. - 246 : 4 (2020), p. 548-559. -
További szerzők:	Bérczes Tamás (1975-) (informatikus) Sztrik János (1953-) (informatikus, matematikus) Kuki Attila (1964-) (informatikus, matematikus) Schreiner, Wolfgang
Pályázati támogatás:	2017-2.2.4-TeT-AT-2017-00010 egyéb
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat Szerző által megadott URL
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001-es BibID:	BIBFORM077598
035-os BibID:	(Scopus)85063076146
Első szerző:	Tóth Ádám (mérnökinformatikus)
Cím:	Comparison of Two Operation Modes of Finite-Source Retrial Queueing Systems with Collisions and a Non-Reliable Server by Using Simulation / Á. Tóth, T. Bérczes, J. Sztrik, A. Kuki
Dátum:	2019
ISSN:	1072-3374 1573-8795
Megjegyzések:	In this paper a finite-source retrial queuing system with collision of the customers is investigated by means of computer simulation. The server is not reliable; it is subjected to breakdowns, and the repairs depend on whether the state of the server is idle. The random variables used in the model are jointly independent and are exponential and gamma distributed. Two operation modes are considered in the case of busy breakdown. The novelty of the investigation is a comparison of the performance measures of these modes, and estimations obtained by the simulation are graphically illustrated showing the influence of the difference of the working modes on the performance measures such as mean and variance of the response time, mean and variance of the number of customers in the system, mean and variance of the sojourn time in the orbit, mean and variance of time time a customer spent in service.
Tárgyszavak:	Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Journal Of Mathematical Sciences. - 237 : 6 (2019), p. 846-857. -
További szerzők:	Bérczes Tamás (1975-) (informatikus) Sztrik János (1953-) (informatikus, matematikus) Kuki Attila (1964-) (informatikus, matematikus)
Pályázati támogatás:	EFOP-3.6.1-16-2016-00022 EFOP EFOP-3.6.2-16-2017-00015 EFOP
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat Szerző által megadott URL
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