Cost Optimization in a GI/M/2/N Queue with Heterogeneous Servers, Working Vacations, and Impatient Customers via the Bat Algorithm

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Publicado en:Mathematics vol. 13, no. 21 (2025), p. 3559-3593
Autor principal: Guendouzi Abdelhak
Otros Autores: Bouzebda Salim
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MDPI AG
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100 1 |a Guendouzi Abdelhak  |u Institute of Science, University Center of Aflou, B. P. 603, Aflou 03001, Algeria 
245 1 |a Cost Optimization in a <i>GI</i>/<i>M</i>/2/<i>N</i> Queue with Heterogeneous Servers, Working Vacations, and Impatient Customers via the Bat Algorithm 
260 |b MDPI AG  |c 2025 
513 |a Journal Article 
520 3 |a This paper analyzes a finite-capacity <inline-formula>GI/M/2/N</inline-formula> queue with two heterogeneous servers operating under a multiple working-vacation policy, Bernoulli feedback, and customer impatience. Using the supplementary-variable technique in tandem with a tailored recursive scheme, we derive the stationary distributions of the system size as observed at pre-arrival instants and at arbitrary epochs. From these, we obtain explicit expressions for key performance metrics, including blocking probability, average reneging rate, mean queue length, mean sojourn time, throughput, and server utilizations. We then embed these metrics in an economic cost function and determine service-rate settings that minimize the total expected cost via the Bat Algorithm. Numerical experiments implemented in R validate the analysis and quantify the managerial impact of the vacation, feedback, and impatience parameters through sensitivity studies. The framework accommodates general renewal arrivals (<inline-formula>GI</inline-formula>), thereby extending classical (<inline-formula>M/M/2/N</inline-formula>) results to more realistic input processes while preserving computational tractability. Beyond methodological interest, the results yield actionable design guidance: (i) they separate Palm and time-stationary viewpoints cleanly under non-Poisson input, (ii) they retain heterogeneity throughout all formulas, and (iii) they provide a cost–optimization pipeline that can be deployed with routine numerical effort. Methodologically, we (i) characterize the generator of the augmented piecewise–deterministic Markov process and prove the existence/uniqueness of the stationary law on the finite state space, (ii) derive an explicit Palm–time conversion formula valid for non-Poisson input, (iii) show that the boundary-value recursion for the Laplace–Stieltjes transforms runs in linear time <inline-formula>O(N)</inline-formula> and is numerically stable, and (iv) provide influence-function (IPA) sensitivities of performance metrics with respect to <inline-formula>(μ1,μ2,ν,α,ϕ,β)</inline-formula>. 
653 |a Customers 
653 |a Customer services 
653 |a Performance measurement 
653 |a Mathematical analysis 
653 |a Cost function 
653 |a Feedback 
653 |a Markov processes 
653 |a Parameter sensitivity 
653 |a Optimization 
653 |a Formulas (mathematics) 
653 |a Algorithms 
653 |a Probability 
653 |a Cost control 
653 |a Queuing theory 
653 |a Economic impact 
653 |a Vacations 
653 |a Heterogeneity 
653 |a Business metrics 
700 1 |a Bouzebda Salim  |u Université de Technologie de Compiègne, LMAC (Laboratory of Applied Mathematics of Compiègne), CS 60 319, 60 203 Compiègne, France 
773 0 |t Mathematics  |g vol. 13, no. 21 (2025), p. 3559-3593 
786 0 |d ProQuest  |t Engineering Database 
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856 4 0 |3 Full Text + Graphics  |u https://www.proquest.com/docview/3271047264/fulltextwithgraphics/embedded/7BTGNMKEMPT1V9Z2?source=fedsrch 
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