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O. Yilmaz et al.<strong>Author</strong> Pro<strong>of</strong>353 351 method first determines a feasible solution via find_feasible, and later uses this solution as352 <strong>the</strong> starting point to determine a feasible solution that generates a reward higher than <strong>the</strong>reward generated by all (C ′ 1 , C′ 2 , C′ 3 , C′ 4 ) combinations.354 <strong>Here</strong> is how find_feasible works: It first determines <strong>the</strong> minimum number <strong>of</strong> channels355 needed by each service call to satisfy <strong>the</strong> QoS constraints. Later it repeats <strong>the</strong> following356 greedy search steps until it finds a near optimal partition allocation. It sets partitions such357 that (a) P 4 contains <strong>the</strong> minimum number <strong>of</strong> channels needed by class 2 new calls; (b) P 3 and358 P 4 contain <strong>the</strong> minimum number <strong>of</strong> channels needed by class 2 hand<strong>of</strong>f calls; (c) P 2 , P 3 and359 P 4 contain <strong>the</strong> minimum number <strong>of</strong> channels needed by class 1 new calls; and (d) finally, P 1360 contains <strong>the</strong> remaining channels. We configure P 4 such that P 1 and P 2 each have a number <strong>of</strong>channels that <strong>are</strong> multiple <strong>of</strong> k 1 361. Later we check if <strong>the</strong> current partition allocation generates362 a feasible solution. If <strong>the</strong> current allocation does not lead a feasible solution, we increase363 <strong>the</strong> minimum number <strong>of</strong> channels needed by each service class that fails to satisfy QoS364 constraints, such that it <strong>can</strong> accommodate one more call. Finally, we adjust <strong>the</strong> number <strong>of</strong>channels available for each service call such that c 1 h ≥ c1 n ≥ c1 h ≥ c1 his preserved and we366 repeat <strong>the</strong>se steps until we find a feasible solution.367 For <strong>the</strong> current partition allocation (C 1 , C 2 , C 3 , C 4 ), find_optimal evaluates all combinations<strong>of</strong> (C ′ 1 , C′ 2 , C′ 3 , C′ 4 ), where C 1 − ∗ k 1 ≤ C ′ 1 ≤ C 1 + ∗ k 1 , C 2 − ∗ k 1 ≤ C ′ 2 ≤369 C 2 + ∗ k 1 , C 3 − ∗ k 2 ≤ C ′ 3 ≤ C 3 + ∗ k 2 , C ′ 4 = C − (C′ 1 + C′ 2 + C′ 3) to determine370 <strong>the</strong> partition allocation that would generate <strong>the</strong> highest reward. If <strong>the</strong> optimal allocation is371 different from <strong>the</strong> current allocation, we set <strong>the</strong> current allocation as <strong>the</strong> optimal and repeat372 evaluation until we determine that <strong>the</strong> current value is optimal.373 While in practice fast spillover CAC takes a much shorter time to execute comp<strong>are</strong>d with374 pure spillover CAC, <strong>the</strong> <strong>the</strong>oretical worst case time complexity <strong>of</strong> this algorithms is stillO(C N 375 ), with C being <strong>the</strong> number <strong>of</strong> channels and N being <strong>the</strong> number <strong>of</strong> service classes376 multiplied by 2, again due to <strong>the</strong> three loops in <strong>the</strong> find_optimal function in Table 2.3774 Numeric Data and Analysis378 We comp<strong>are</strong> spillover-partitioning algorithm with existing CAC algorithms with revenue opti-379 mization and QoS guarantees, including partitioning, threshold-based, partitioning-threshold380 hybrid CAC algorithms [24] in terms <strong>of</strong> execution time and revenue maximization. We briefly381 explain <strong>the</strong>se baseline CAC algorithms as follows. Partitioning CAC divides <strong>the</strong> total number382 <strong>of</strong> channels into several fixed partitions, with each partition being reserved to serve hand<strong>of</strong>f383 or new calls <strong>of</strong> a particular service class. For our example system <strong>the</strong>re <strong>are</strong> four partitions:384 class 1 hand<strong>of</strong>f calls, class 1 new calls, class 2 hand<strong>of</strong>f calls, and class 2 new calls. Once385 a partition is reserved, it <strong>can</strong>not be used by o<strong>the</strong>rs. Thus, each partition may be modeled386 as an M/M/n/n queue by which <strong>the</strong> rejection/blocking probability in each partition <strong>can</strong> be387 easily calculated as <strong>the</strong> probability <strong>of</strong> not being able to serve one more call in that specificpartition. The optimization problem here is to find <strong>the</strong> best partition (C 1 h , C1 n , C2 h , C2 n )such that C 1 h + C1 n + C2 h + C2 n = C with reward optimization and QoS guarantees. Threshold-basedCAC creates thresholds to differentiate hand<strong>of</strong>f calls from new calls, viz., C 1 390hTis <strong>the</strong> threshold for class 1 hand<strong>of</strong>f calls; C 1 nT is <strong>the</strong> threshold for class 1 new calls; C2 hT is<strong>the</strong> threshold for class 2 hand<strong>of</strong>f calls; and C 2 nTis <strong>the</strong> threshold for class 2 new calls. The393 meaning <strong>of</strong> a threshold is that when <strong>the</strong> total number <strong>of</strong> channels already allocated exceeds394 this threshold, <strong>the</strong> system will not admit calls <strong>of</strong> <strong>the</strong> corresponding service type any more.The optimization problem is to find <strong>the</strong> best set <strong>of</strong> thresholds (C 1 hT , C1 nT , C2 hT , C2 nT) such thatC 1 nT ≤ C, C1 hT ≤ C, C2 nT ≤ CandC2 hT≤ C with reward optimization and QoS satisfaction.396123uncorrected pro<strong>of</strong>Journal: 11277 MS: WIRE823 CMS: 11277_2009_9673_Article TYPESET DISK LE CP Disp.:2009/2/19 Pages: 21 Layout: Small

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