Splittable tra c partition in WDM = SONET rings to minimize SONET
نویسنده
چکیده
SONET ADMs are the dominant cost factor in the WDM=SONET rings. Recently several articles (Belvaux et al., European J. Oper. Res. 108 (1) (1998) 26–35; C+ alinescu and Wan, Tra c partition in WDM=SONET rings to minimize SONET ADMs, submitted for publication; Gerstel et al., Proc. IEEE INFOCOM’98, vol. 1, pp. 94–101; Liu et al., Proc. INFOCOM, vol. 2, 2000, pp. 1020–1025; Sutter et al., Oper. Res. 46 (5) (1998) 719–728) proposed a number of heuristics for tra c partition so as to use as few SONET ADMs as possible. Most of these heuristics assumes wavelength-continuity, i.e., the same wavelength is allocated on all of the links in the path established for a tra c stream. It was Arst observed and argued by Gerstel et al. that the number of ADMs can be potentially reduced by allowing a tra c stream to be locally transferred from one ADM in a wavelength to another ADM in a diBerent wavelength at any intermediate node, in other words, the tra c streams are splittable. In this paper, we study two variations of this minimum ADM problem with splittable tra c streams: all tra c streams have prespeciAed routings, and all tra c streams have no prespeciAed routings respectively. Both variations are shown to be NP-hard. For the former variation, a heuristic with approximation ratio at most 5=4 is proposed. For the latter variation, a similar heuristic with approximation ratio 3=2 is proposed. c © 2002 Published by Elsevier Science B.V.
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