09.07.2015 Views

Dear Author, Here are the proofs of your article. • You can submit ...

Dear Author, Here are the proofs of your article. • You can submit ...

Dear Author, Here are the proofs of your article. • You can submit ...

SHOW MORE
SHOW LESS
  • No tags were found...

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Performance Analysis <strong>of</strong> Spillover-Partitioning Call Admission Control<strong>Author</strong> Pro<strong>of</strong>473474475476477478479480481482483484485efficiency by spillover-partitioning makes it practically possible to obtain at least near-optimalsolutions to be applied at runtime, comp<strong>are</strong>d with threshold-based CAC algorithms,which, because <strong>of</strong> high computational complexity, would take days to obtain a solution.4.2.1 Sensitivity Analysis <strong>of</strong> Solution QualityRecall that fast spillover CAC consists <strong>of</strong> two phases. The first phase searches for a feasibleinitial solution. The second phase performs a greedy search to increase <strong>the</strong> solution quality.The greedy search continues until <strong>the</strong> algorithm <strong>can</strong>not improve <strong>the</strong> solution quality any fur<strong>the</strong>r.Therefore, <strong>the</strong> initial solution conceivably may have a high impact on <strong>the</strong> final solutionquality. Below we perform a sensitivity analysis to test <strong>the</strong> sensitivity <strong>of</strong> <strong>the</strong> solution quality<strong>of</strong> <strong>the</strong> initial solution (relative to <strong>the</strong> solution found by pure spillover CAC) with respect to<strong>the</strong> traffic demand and QoS constraints, and see whe<strong>the</strong>r it affects <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong>final solution <strong>of</strong> fast spillover CAC.Figure 8 shows <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong> initial solution as <strong>the</strong> traffic demand increases,going from case 1 with λ 1 486 h = 3.66,λ1 n = 7.32,λ2 h = 2.69, and λ2 n = 3.59 to case 12 withλ 1 487 h = 3.66,λ1 n = 7.32,λ2 h = 5.99, and λ2 n = 7.98. We observe that <strong>the</strong> solution quality <strong>of</strong>488 <strong>the</strong> initial solution relative to that <strong>of</strong> <strong>the</strong> pure spillover algorithm remains about <strong>the</strong> same and489 is largely insensitive to <strong>the</strong> traffic demand, with <strong>the</strong> minimum solution quality ratio at 0.96490 and <strong>the</strong> maximum solution quality ratio at 0.98. Figure 8 also shows <strong>the</strong> solution quality <strong>of</strong>491 <strong>the</strong> final solution found by fast spillover CAC. We see that <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong> final492 solution found by fast spillover CAC is largely insensitive to <strong>the</strong> initial solution found in <strong>the</strong>493 first phase <strong>of</strong> <strong>the</strong> algorithm.494 Figure 9 shows <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong> initial solution as we reduce QoS constraints,going from case 1 with B 1 495 h t = 0.01, B1 n t = 0.025, B2 h t = 0.02, and B2 nt = 0.05 to case 5with B 1 496 h t = 0.05, B1 n t = 0.125, B2 h t = 0.1, and B2 nt = 0.25. The figure shows three traffic497 demand cases, namely, high, medium, and low. We see that in all traffic demand cases when498 QoS constraints <strong>are</strong> reduced (made less stringent), <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong> initial solution499 decreases because less stringent QoS constraints allow <strong>the</strong> find_feasible function to find a500 solution more easily. This indicates that <strong>the</strong> initial solution is sensitive to QoS constraints.501 However, <strong>the</strong> final solution result found by <strong>the</strong> greedy search remains <strong>the</strong> same regardless <strong>of</strong>502 <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong> initial solution. We conclude that <strong>the</strong> solution quality <strong>of</strong> <strong>the</strong> finaluncorrected pro<strong>of</strong>Fig. 8 Sensitivity <strong>of</strong> initial solution quality with respect to traffic demand123Journal: 11277 MS: WIRE823 CMS: 11277_2009_9673_Article TYPESET DISK LE CP Disp.:2009/2/19 Pages: 21 Layout: Small

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!