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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Routing and wavelength assignment ： ウィキペディア英語版 Routing and wavelength assignment The routing and wavelength assignment (RWA) problem is an optical networking problem with the goal of maximizing the number of optical connections. == Definition == The general objective of the RWA problem is to maximize the number of established connections. Each connection request must be given a route and wavelength. The wavelength must be consistent for the entire path, unless the usage of wavelength converters is assumed. Two connections requests can share the same optical link, provided a different wavelength is used. The RWA problem can be formally defined in an integer linear program (ILP). The ILP formulation given here is taken from.〔H. Zang, J. Jue, and B. Mukherjee, "A Review of Routing and Wavelength Assignment Approaches for Wavelength Routed Optical WDM Networks," , January 2000.〕 Maximize: :$C\_0(\backslash rho,q)\; =\; \backslash sum\_^$ :$c\_\; \backslash in\; ,\; i\; =\; 1,\; 2,\; ...,\; P,\; j\; =\; 1,\; 2,\; ...,\; W$ :$C^TB\; \backslash leq\; l\_$ :$m\; \backslash leq\; 1\_WC^TA$ :$m\_i\; \backslash leq\; q\_i\backslash rho,\; i\; =\; 1,\; 2,\; ...,\; N\_$ $N\_$ is the number of source-destination pairs, while $m\_i$ is the number of connections established for each source-destination pair. $L$ is the number of links and $W$ is the number of wavelengths. $P$ is the set of paths to route connections. $A:P\; \backslash times\; N\_$ is a matrix which shows which source-destination pairs are active, $B:P\; \backslash times\; L$ is a matrix which shows which links are active, and $C:P\; \backslash times\; W$ is a route and wavelength assignment matrix. Note that the above formulation assumes that the traffic demands are known ''a priori''. This type of problem is known as Static Lightpath Establishment (SLE). The above formulation also does not consider the signal quality. It has been shown that the SLE RWA problem is NP-complete in.〔I. Chlamtac, A. Ganz, and G. Karmi, "Lightpath communications: an approach to high bandwidth optical WAN's," , Vol 40, No 7, pp. 1171-1182, July 1992.〕 The proof involves a reduction to the $n$-graph colorability problem. In other words, solving the SLE RWA problem is as complex as finding the chromatic number of a general graph. Given that dynamic RWA is more complex than static RWA, it must be the case that dynamic RWA is also NP-complete. Another NP-complete proof is given in.〔S. Evan, A. Itai, and A. Shamir, "On the Complexity of Timetable and Multicommodity Flow Problems," SIAM Journal of Computing, Vol 5, pp 691-703, 1976〕 This proof involves a reduction to the Multi-commodity Flow Problem. The RWA problem is further complicated by the need to consider signal quality. Many of the optical impairments are nonlinear, so a standard shortest path algorithm can't be used to solve them optimally even if we know the exact state of the network. This is usually not a safe assumption, so solutions need to be efficient using only limited network information. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Routing and wavelength assignment」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.