| 1. |
- Yavuz, Emre A., et al.
(författare)
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A practical method for estimating performance metrics of call admission control schemes in wireless mobile networks
- 2005
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Ingår i: 2005 IEEE Wireless Communications and Networking Conference, Vols 1-4. - 0780389662 ; , s. 1254-1259
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Konferensbidrag (refereegranskat)abstract
- Providing the desired call blocking probability to not only new but also existing calls has been a challenge for wireless mobile network service providers. To satisfy different requirements for new and handoff call blocking probabilities, several call admission control (CAC) schemes have been proposed in the literature. Exact analysis of these schemes using two dimensional Markov chain is computationally intensive. Therefore under specific assumptions computationally efficient methods to analyze these systems using one dimensional Markov chain models have been considered. The "traditional" approach assumes that channel holding time for new and handoff calls have equal mean values. While the "normalized" approach relaxes this assumption, it is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing call blocking probabilities for several widely known call admission control schemes under more general assumptions by providing an easy to implement method. The numerical results show that when the average values of channel holding times for new and handoff calls are different, the proposed approach gives more accurate results when compared with the traditional and normalized methods based on one dimensional Markov chain modeling, while keeping the computational complexity low.
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| 2. |
- Yavuz, Emre A., et al.
(författare)
-
Computationally efficient method to evaluate the performance of guard-channel-based call admission control in cellular networks
- 2006
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 55:4, s. 1412-1424
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Tidskriftsartikel (refereegranskat)abstract
- Many guard-channel-based call admission control (CAC) schemes for cellular networks have been proposed to provide the desired quality of service to not only new calls but also ongoing calls when they hand off to neighboring cells. Blocking/dropping probabilities of new/handoff calls are generally analyzed using one-dimensional Markov chain modeling under specific assumptions to avoid solving large sets of flow equations that makes exact analyses of these schemes using multidimensional Markov chain models infeasible. This is the case with the "traditional" approach, which assumes that channel holding times for new and handoff calls have equal mean values, and the "normalized" approach, which relaxes this assumption but is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing new/handoff call blocking/dropping probabilities for several widely known CAC schemes and develop an easy-to-implement method under more general assumptions. Numerical results show that when the mean channel holding times for new and handoff calls are different, the proposed "effective holding time" approach gives more accurate results compared with the traditional and the normalized methods while keeping the computational complexity low. The accuracy of these methods and their levels of computational complexity with the exact solution are also compared.
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| 3. |
- Yavuz, Emre A., et al.
(författare)
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Efficient approximations for call admission control performance evaluations in multi-service networks
- 2006
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Ingår i: GLOBECOM 2006. - 9781424403561
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Konferensbidrag (refereegranskat)abstract
- Several dynamic call admission control (CAC) schemes for cellular networks have been proposed in the literature to reserve resources adaptively to provide the desired quality of service (QoS) to not only high priority calls but also to low priority ones. Efficient adaptive reservations depend on reliable and up-to-date system status feedback provided to the CAC mechanism. However exact analysis of these schemes using multidimensional Markov chain models are intractable in real time due to the need to solve large sets of flow equations. Hence performance metrics such as call blocking probabilities of various QoS classes are generally evaluated using one dimensional Markov chain models assuming that channel occupancy times for all QoS classes have equal mean values and all arriving calls have equal capacity requirements. In this paper we re-evaluate the analytical methods to compute call blocking probabilities of various QoS classes for several widely known CAC schemes by relaxing these assumptions, and propose a novel approximation method for performance evaluation with low computational complexity. Numerical results show that proposed method provides results that match well with the exact solutions.
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| 4. |
- Yavuz, Emre A., et al.
(författare)
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Efficient Methods for Performance Evaluations of Call Admission Control Schemes in Multi-Service Cellular Networks
- 2008
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 7:9, s. 3468-3476
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Tidskriftsartikel (refereegranskat)abstract
- Many dynamic call admission control (CAC) schemes have been proposed in the literature for adaptive reservations in cellular networks. Efficient application of these schemes requires reliable and up-to-date feedback of system performance to the CAC mechanism. However, exact analyses of these schemes in real time using multi-dimensional Markov chain models are challenging due to the need to solve large sets of flow equations. One dimensional Markov chain models have been widely used to derive performance metrics such as call blocking probabilities of multiple traffic classes assuming that all classes of calls have equal capacity requirements and exponentially distributed channel holding times with equal mean values. These assumptions need to be relaxed for a more general evaluation of CAC performance in multi-service cellular networks. In this paper we classify CAC schemes according to their Markov chain models into two categories: symmetric and asymmetric, and develop computationally efficient analytical methods to compute call blocking probabilities of various traffic classes for several widely known CAC schemes under relaxed assumptions. We obtain a product form solution to evaluate symmetric schemes and propose a novel performance evaluation approximation method with low computational cost for asymmetric schemes. Numerical results demonstrate the accuracy and efficiency of the proposed method.
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| 5. |
- Yavuz, Emre A., et al.
(författare)
-
Modelling channel occupancy times for voice traffic in cellular networks
- 2007
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Ingår i: 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-14. - 9781424403523 ; , s. 332-337
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Konferensbidrag (refereegranskat)abstract
- Call holding times in telephony networks are commonly approximated by exponential distributions to facilitate traffic engineering. However, for traffic engineering of cellular networks, channel occupancy times need to be modeled instead to facilitate analytical modeling or to feed network simulations. In this paper, we classify channel occupancy times and present an empirical study based on data obtained from a real cellular network to determine which probability distribution functions can approximate them better. The results are environment dependent, but no assumptions that can be influential are made, as opposed to previous analytical and simulation studies which results are highly dependent on the assumptions made by the authors. We show that all types of channel occupancy times can be approximated by lognormal distribution. For stationary users, channel occupancy times are commonly approximated by exponential distribution due to its tractability, assuming that cell residence times are also exponentially distributed. However, we show that lognormal distribution fits much better to both channel occupancy and call holding times regardless of whether users are stationary or mobile.
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