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Performance Evaluation of the Threshold Call Admission Policy in Multi-rate Loss Systems

Moscholios Ioannis D., Chousainov Iskanter-Alexandros, Panagoulias Panagiotis I., Sarigiannidis Panagiotis G., Logothetis Michael D.

Journal of Telecommunications and Information Technology

2020

nr 2

51--60

In this paper we consider a link, characterized by speciﬁc capacity, that services multi-rate random or quasirandom traﬃc. Random traﬃc is generated by an inﬁnite number of traﬃc sources, while quasi-random traﬃc is generated by a ﬁnite population of traﬃc sources. The link is modeled as a multi-rate loss system. Handover and new calls are distinguished. New calls compete for the available bandwidth under a threshold call admission policy. In that policy, a new call of a particular service-class is not allowed to enter the system if the in-service handover and new calls of the same service-class plus the new call, exceed a predeﬁned threshold (which can be diﬀerent for each service-class). On the other hand, handover calls compete for the available bandwidth based on the complete sharing policy. We show that the steady state probabilities in the proposed models have a product form solution (PFS). The PFS leads to a convolution algorithm for accurate calculation of congestion probabilities and link utilization.

Performance metrics in OFDM wireless networks supporting quasi-random traffic

Panagoulias P., Moscholios I., Sarigiannidis P., Piechowiak M., Logothetis M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2020

Vol. 68, nr 2

215--223

We consider the downlink of an orthogonal frequency division multiplexing (OFDM) based cell that accommodates calls from different service-classes with different resource requirements. We assume that calls arrive in the cell according to a quasi-random process, i.e., calls are generated by a finite number of sources. To calculate the most important performance metrics in this OFDM-based cell, i.e., congestion probabilities and resource utilization, we model it as a multirate loss model, show that the steady-state probabilities have a product form solution (PFS) and propose recursive formulas which reduce the complexity of the calculations. In addition, we study the bandwidth reservation (BR) policy which can be used in order to reserve subcarriers in favor of calls with high subcarrier requirements. The existence of the BR policy destroys the PFS of the steady-state probabilities. However, it is shown that there are recursive formulas for the determination of the various performance measures. The accuracy of the proposed formulas is verified via simulation and found to be satisfactory.

Low Discrepancy Initialized Particle Swarm Optimization for Solving Constrained Optimization Problems

Pant M., Thangaraj R., Abraham A.

Fundamenta Informaticae

2009

Vol. 95, nr 4

511-531

Population based metaheuristics are commonly used for global optimization problems. These techniques depend largely on the generation of initial population. A good initial population may not only result in a better fitness function value but may also help in faster convergence. Although these techniques have been popular since more than three decades very little research has been done on the initialization of the population. In this paper, we propose a modified Particle Swarm Optimization (PSO) called Improved Constraint Particle Swarm Optimization (ICPSO) algorithm for solving constrained optimization. The proposed ICPSO algorithm is initialized using quasi random Vander Corput sequence and differs from unconstrained PSO algorithm in the phase of updating the position vectors and sorting every generation solutions. The performance of ICPSO algorithm is validated on eighteen constrained benchmark problems. The numerical results show that the proposed algorithm is a quite promising for solving constraint optimization problems.