The present investigation deals with the performance prediction of finite Markovian retrial queues with unreliable server. The arrivals of the customers follow geometric distribution while the service pattern follows exponential distribution. The customers are served in two stages i.e. first essential service (FES) which is compulsory for all the arriving customers and second optional service (...

The advantages in modularity and power of microkernel-based operating systems such as Mach 3.0 are well known. The existing performance problems of these systems, however, are signi cant. Much of the performance degradation is due to the cost of maintaining separate protection domains, traversing software layers, and using a semantically rich inter-process communication mechanism. An approach t...

In this chapter we provide an overview of the application of the results obtained in Sensoria (i.e., techniques, methods and languages developed in the technical work packages WP1-WP7) to case studies from the Automotive, eUniversity, Finance and Telecommunication domains (developed in work package WP8).

Studies based on British Crime Survey (BCS) data suggest that the overall incidence of workplace assault is relatively low. However, these data have a number of limitations. They include only assaults carried out by clients or the public, provide limited information about the individuals involved and their workplaces, and tell us little about perceived causes of violence at work. The 2008 Workp...

Jackson networks are versatile models for analyzing complex networks. In this paper we study generalized Jackson networks with single-server stations, where nodes may have an infinite supply of work. We allow simultaneous breakdown of servers and consider group repair strategies. We establish the existence of a steadystate distribution of the queue-length vector at stable nodes for different ty...

Broadband communications are concerned with various types of failures, varying from single link failures such as fibre cuts, inline equipment breakdown to multiple network failures which significantly affects the backbone of the Internet. Alternative routing schemes and backup metholodgy is needed to recovery from link failures. In this paper we propose a multipath routing schemes for various l...

Modelsandanalyticaltechniquesaredevelopedtoevaluatetheperformanceoftwovariationsof singlebuffers(conventionalandbufferrelaxationsystem)multiplequeuessystem.Intheconventional system,eachqueuecanhaveatmostonecustomeratanytimeandnewlyarrivingcustomersfindthe bufferfullarelost.Inthebufferrelaxationsystem,thequeuebeingservedmayhavetwocusto...

Accurate and reliable time is necessary for financial and legal transactions, transportation, distribution systems, and many other applications. Time synchronization protocols such as NTP (the Network Time Protocol) have kept clocks of such applications synchronized to each other for many years. Nowadays there are many commercial GPS based NTP time server products at the market but they almost ...

a single server queue with bernoulli vacation has been considered. in addition the admission to queue is based on a bernoulli process and the server gives two type of services. for this model the probability generating function for the number of customers in the queue at different server's state are obtained using supplementary variable technique. some performance measures are calculated. ...