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23
Dynamic admission control in a call center with one shared and two dedicated service facilities
, 2002
"... Calls of two classes arrive at a call center according to two independent Poisson processes. The center has two dedicated stations, one for each class, and one shared station. All three stations consist of parallel servers and no waiting room. Calls of each type demand exponential service times wit ..."
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Cited by 13 (2 self)
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Calls of two classes arrive at a call center according to two independent Poisson processes. The center has two dedicated stations, one for each class, and one shared station. All three stations consist of parallel servers and no waiting room. Calls of each type demand exponential service times with different service rates and generate different rewards. Moreover, the service rates are different in the shared and dedicated stations. We assume nonpreemptive service. Our objective is to derive the structure of dynamic admission policies that maximize the total expected discounted revenue over an innite horizon as well as the longrun average revenue. We show that it is optimal to serve a customer in her dedicated station whenever it is possible. For the shared station, we derive a sufcient condition for each class under which it is always optimal to accept customers of that class to the shared station if the dedicated station is full and the shared station has available servers. Furthermore, the optimal admission policy at the shared station can be characterized as a monotonic threshold policy.
Admission control policies in multiservice cellular networks: optimum configuration and sensitivity
 Wireless Systems and Mobility in Next Generation Internet, Gabriele Kotsis and Otto Spaniol (eds.), Lecture Notes in Computer Science (LNCS
, 2005
"... Abstract. We evaluate different call admission control policies in various multiservice cellular scenarios. For each of the studied policies we obtain the maximum calling rate that can be offered to the system to achieve a given QoS objective defined in terms of blocking probabilities. We propose a ..."
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Cited by 6 (4 self)
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Abstract. We evaluate different call admission control policies in various multiservice cellular scenarios. For each of the studied policies we obtain the maximum calling rate that can be offered to the system to achieve a given QoS objective defined in terms of blocking probabilities. We propose an optimization methodology based on a hill climbing algorithm to find the optimum configuration for most policies. The results show that policies of the trunk reservation class outperform policies that produce a productform solution and the improvement ranges approximately between 5 and 15 % in the scenarios studied. 1
Optimal and Structured Call Admission Control Policies for ResourceSharing Systems
"... Abstract—Many communication and networking systems can be modeled as resourcesharing systems with multiple classes of calls. Call admission control (CAC) is an essential component of such systems. Markov decision process (MDP) tools can be applied to analyze and compute the optimal CAC policy that ..."
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Cited by 5 (0 self)
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Abstract—Many communication and networking systems can be modeled as resourcesharing systems with multiple classes of calls. Call admission control (CAC) is an essential component of such systems. Markov decision process (MDP) tools can be applied to analyze and compute the optimal CAC policy that optimizes certain performance metrics of the system. But for most practical systems, it is prohibitively difficult to compute the optimal CAC policy using any MDP algorithm because of the “curse of dimensionality.” We are, therefore, motivated to consider two families of structured CAC policies: reservation and threshold policies. These policies are easy to implement and have good performance in practice. However, since the number of structured policies grows exponentially with the number of call classes and the capacity of the system, finding the optimal structured policy is a complex unsolved problem. In this paper, we develop fast and efficient search algorithms to determine the parameters of the structured policies. We prove the convergence of the algorithms. Through extensive numerical experiments, we show that the search algorithms converge quickly and work for systems with large capacity and many call classes. In addition, the returned structured policies have optimal or nearoptimal performance, and outperform those structured policies with parameters chosen based on simple heuristics. Index Terms—Call admission control (CAC), combinatorial optimization, Markov decision process (MDP), reservation policy, resource sharing, threshold policy. I.
Comparative evaluation of admission control policies in cellular multiservice networks
 in Proceedings of the 16th International Conference on Wireless Communications
, 2004
"... Abstract. We evaluate different call admission control policies in various multiservice cellular scenarios. For each of the studied policies we obtain the maximum calling rate that can be offered to the system to achieve a given QoS objective defined in terms of blocking probabilities. We propose an ..."
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Cited by 5 (2 self)
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Abstract. We evaluate different call admission control policies in various multiservice cellular scenarios. For each of the studied policies we obtain the maximum calling rate that can be offered to the system to achieve a given QoS objective defined in terms of blocking probabilities. We propose an optimization methodology based on a hill climbing algorithm to find the optimum configuration for most policies. Preliminary results show that policies of the trunk reservation class outperform policies that produce a productform solution and the improvement ranges approximately between 5 and 15%.
Structured Admission Control Policy in Heterogeneous Wireless Networks with Mesh Underlay
"... Abstract—In this paper, we investigate into optimal admission control policies for Heterogeneous Wireless Networks (HWN), considering an integration of wireless mesh networks with an overlaying cellular infrastructure. In order to characterize the overflow traffic from the underlaying mesh to the ov ..."
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Cited by 3 (3 self)
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Abstract—In this paper, we investigate into optimal admission control policies for Heterogeneous Wireless Networks (HWN), considering an integration of wireless mesh networks with an overlaying cellular infrastructure. In order to characterize the overflow traffic from the underlaying mesh to the overlay, a PartiallyObservable MarkovModulated Poisson Process (POMMPP) traffic model is developed. This model captures the burstiness of the overflow traffic under the imperfect observability of the mesh network states. Then, by modeling the overlay network as a controlled POMMPP/M/C/C queueing system and obtaining structured decision theoretic results, it is shown that the optimal control policies for this class of HWNs can be characterized as monotonic threshold curves. Further, these results are used to design a computationally efficient algorithm to determine the optimal policy in terms of thresholds. Numerical observations suggest that the proposed algorithm is efficient in terms of timecomplexity and can drastically reduce the cost of dropped and blocked calls. I.
Threshold and reservation based call admission control policies for multiservice resourcesharing systems
 in Proc. IEEE INFOCOM
"... Abstract — Many communications and networking systems can be modelled as resourcesharing systems with multiple classes of calls. Call admission control (CAC) is an essential component of such systems. For most practical systems it is prohibitively difficult to compute the optimal CAC policy that op ..."
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Cited by 3 (1 self)
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Abstract — Many communications and networking systems can be modelled as resourcesharing systems with multiple classes of calls. Call admission control (CAC) is an essential component of such systems. For most practical systems it is prohibitively difficult to compute the optimal CAC policy that optimizes certain performance metrics because of the ‘curse of dimensionality’. In this paper we study two families of structured CAC policies: threshold and reservation policies. These policies are easy to implement and have good performance in practice. However, since the number of structured policies grows exponentially with the number of call classes and the capacity of the system, finding the optimal structured policies is a complex unsolved problem. In this paper efficient search algorithms are proposed to find the coordinate optimal structured policies among all structured policies. Through extensive numerical experiments we show that the search algorithms converge quickly and work for systems with large capacity and many call classes. In addition, the returned structured policies have optimal or nearoptimal performance, and outperform those structured policies with parameters chosen based on simple heuristics. Keywords—Resource sharing, call admission control, threshold policies, reservation policies, combinatorial optimization. I.
Dynamic wavelength sharing policies for absolute QoS guarantees
 in OBS networks,” in Proc. IEEE Globecom
, 2006
"... Abstract — We consider the problem of providing absolute QoS guarantees to multiple classes of users of an OBS network in terms of the endtoend burst loss. We employ Markov decision process (MDP) theory to develop wavelength sharing policies that maximize throughput while meeting the QoS guarantee ..."
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Abstract — We consider the problem of providing absolute QoS guarantees to multiple classes of users of an OBS network in terms of the endtoend burst loss. We employ Markov decision process (MDP) theory to develop wavelength sharing policies that maximize throughput while meeting the QoS guarantees. The randomized threshold policies we obtain are simple to implement and operate, and make effective use of statistical multiplexing. I.
Dynamic CrossSelling in Call Centers
, 2004
"... This paper models the crossselling problem of a call center as a dynamic admission control problem. The key tradeoff between revenue generation and congestion in a call center is addressed in a dynamic framework. The question of when and to whom to crosssell is explored using this model. The analys ..."
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This paper models the crossselling problem of a call center as a dynamic admission control problem. The key tradeoff between revenue generation and congestion in a call center is addressed in a dynamic framework. The question of when and to whom to crosssell is explored using this model. The analysis shows that unlike current marketing practice which targets crosssell attempts to entire customer segments, optimal dynamic policies may target selected customers from different segments. Structural properties of optimal policies are explored. Sufficient conditions are established for the existence of preferred calls and classes; i.e. calls that will always generate a crosssell attempt. Numerical examples, that are motivated by a real call center, identify call center characteristics that increase the significance of considering dynamic policies rather than simple static crossselling rules as currently observed. The value of these dynamic policies and static rules are compared. Finally, the structural properties lead to a heuristic that generates sophisticated static rules leading to near optimal performance. 1
transfers in grid networks
, 2006
"... A flexible bandwidth reservation framework for bulk data transfers in grid networks ..."
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A flexible bandwidth reservation framework for bulk data transfers in grid networks
1 Efficient Structured Policies for Admission Control in Heterogeneous Wireless Networks
"... Abstract—In the near future, demand for Heterogeneous Wireless Networking (HWN) is expected to to increase. QoS provisioning in these networks is a challenging issue considering the diversity in wireless networking technologies and the existence of mobile users with different communication requireme ..."
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Abstract—In the near future, demand for Heterogeneous Wireless Networking (HWN) is expected to to increase. QoS provisioning in these networks is a challenging issue considering the diversity in wireless networking technologies and the existence of mobile users with different communication requirements. In HWNs with their increased complexity, “the curse of dimensionality” problem makes it impractical to directly apply the decision theoretic optimal control methods that are previously used in homogeneous wireless networks to achieve desired QoS levels. In this paper, optimal call admission control policies for HWNs are considered. A decision theoretic framework for the problem is derived by a dynamic programming formulation. We prove that for a twotier wireless network architecture, the optimal policy has a twodimensional threshold structure. Further, this structural result is used to design two computationally efficient algorithms, Structured Value Iteration and Structured Update Value Iteration. These algorithms can be used to determine the optimal policy in terms of thresholds. Although the first one is closer in its operation to the conventional Value Iteration algorithm, the second one has a significantly lower complexity. Extensive numerical observations suggest that, for all practical parameter sets, the algorithms always converge to the overall optimal policy. Further, the numerical results show that the proposed algorithms are efficient in terms of timecomplexity and in achieving the optimal performance. Index Terms—Stochastic optimal control, quality of service, markov processes. I.