ILP formulations for p-cycle design without candidate cycle enumeration

The concept of p-cycle (preconfigured protection cycle) allows fast and efficient span protection in wavelength division multiplexing (WDM) mesh networks. To design p-cycles for a given network, conventional algorithms need to enumerate cycles in the network to form a candidate set, and then use an integer linear program (ILP) to find a set of p-cycles from the candidate set. Because the size of the candidate set increases exponentially with the network size, candidate cycle enumeration introduces a huge number of ILP variables and slows down the optimization process. In this paper, we focus on p-cycle design without candidate cycle enumeration. Three ILPs for solving the problem of spare capacity placement (SCP) are first formulated. They are based on recursion, flow conservation, and cycle exclusion, respectively. We show that the number of ILP variables/constraints in our cycle exclusion approach only increases linearly with the network size. Then, based on cycle exclusion, we formulate an ILP for solving the joint capacity placement (JCP) problem. Numerical results show that our ILPs are very efficient in generating p-cycle solutions. © 2009 IEEE.published_or_final_versio

Monitoring trail: on fast link failure localization in all-optical WDM mesh networks

We consider an optical layer monitoring mechanism for fast link failure localization in all-optical wavelength-division-multiplexing (WDM) mesh networks. A novel framework of all-optical monitoring, called monitoring trail (m-trail), is introduced. It differs from the existing monitoring cycle (m-cycle) method by removing the cycle constraint. As a result, m-trail provides a general all-optical monitoring structure, which includes simple, nonsimple m-cycles, and open trails as special cases. Based on an in-depth theoretical analysis, we formulate an efficient integer linear program (ILP) for m-trail design to achieve unambiguous localization of each link failure. The objective is to minimize the monitoring cost (i.e., monitor cost plus bandwidth cost) of all m-trails in the solution. Numerical results show that the proposed m-trail scheme significantly outperforms its m-cycle-based counterpart.published_or_final_versio

Monitoring Cycle Design for Fast Link Failure Localization in All-Optical Networks

A monitoring cycle (m-cycle) is a preconfigured optical loop-back connection of supervisory wavelengths with a dedicated monitor. In an all-optical network (AON), if a link fails, the supervisory optical signals in a set of m-cycles covering this link will be disrupted. The link failure can be localized using the alarm code generated by the corresponding monitors. In this paper, we first formulate an optimal integer linear program (ILP) for m-cycle design. The objective is to minimize the monitoring cost which consists of the monitor cost and the bandwidth cost (i.e., supervisory wavelength-links). To reduce the ILP running time, a heuristic ILP is also formulated. To the best of our survey, this is the first effort in m-cycle design using ILP, and it leads to two contributions: 1) nonsimple m-cycles are considered; and 2) an efficient tradeoff is allowed between the monitor cost and the bandwidth cost. Numerical results show that our ILP-based approach outperforms the existing m-cycle design algorithms with a significant performance gain.published_or_final_versio

Effect of seed size and storage on the germination of Artocarpus altilis (Parkinson: Forsberg)

A study was designed to assess the effect of seed size and storage on the germination of Artocarpus altilis seeds. Six fallen pods were collected under the mother tree and seed length (cm) and diameter (cm) measured while germination treatments were fresh intact seeds (FIS), separated into six pod origin, A, B, C, E, F, and G pods (control), testa removed seeds (TRS), 1day storage (1DS), 7days storage (7DS), and 14 days storage (14DS) in a completely randomized experimental design. The results showed that there is a significant difference (p<0.05) in seed length and diameter among the pods studied. There was however no significant difference (p>0.05) in dormancy period, number of days to complete germination, germination capacity (%), germination speed and uniformity of germination. Testa removal however improved germination of Artocarpus altilis seeds. Furthermore storage negatively affected the germination of the seeds while immediate sowing after processing of fresh seeds improved germination. Arthocarpus altilis seeds are therefore recalcitrant and will require the establishment of field genebanks to preserve and conserve the species germplasm. Moreover to propagate the plant from seed care must be taken to select large seeds so as to improve the quality of seedlings produced. Keyword: Germination, seed, germplasm, conservation, preservatio

An adaptive interpolating MLS based response surface model applied to design optimizations of electromagnetic devices

Author name used in this publication: S. L. HoAuthor name used in this publication: S. Y. Yang2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A combined wavelet-FE method for transient electromagnetic-field computations

Author name used in this publication: S. Y. YangAuthor name used in this publication: S. L. HoAuthor name used in this publication: G. Z. Ni2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

An adaptive interpolating moving least squares response surface model applied to the design optimizations of electromagnetic devices

Author name used in this publication: S. L. HoAuthor name used in this publication: S. Y. YangVersion of RecordPublishe

Optical layer monitoring schemes for fast link failure localization in all-optical networks

Optical layer monitoring and fault localization serves as a critical functional module in the control and management of optical networks. An efficient monitoring scheme aims at minimizing not only the hardware cost required for 100{%} link failure localization, but also the number of redundant alarms and monitors such that the network fault management can be simplified as well. In recent years, several optical layer monitoring schemes were reported for fast and efficient link failure localization, including simple, non-simple monitoring cycle (m-cycle) and monitoring trail (m-trail). Optimal ILP (Integer Linear Program) models and heuristics were also proposed with smart design philosophy on flexibly trading off different objectives. This article summarizes those innovative ideas and methodologies with in-depth analysis on their pros and cons. We also provide insights on future research topics in this area, as well as possible ways for extending the new failure localization approaches to other network applications. © 2005 IEEE.published_or_final_versio

CFP: Cooperative fast protection

Article number: 5062196The 28th Conference on Computer Communications, IEEE INFOCOM 2009, Miniconference, Rio de Janeiro, Brazil, 19-25 April 2009We introduce Cooperative Fast Protection (CFP) as a novel protection scheme in WDM networks. CFP achieves capacity-efficient fast protection with the features of node-autonomy and failure-independency. It differs from p-cycle by reusing the released working capacity of the disrupted lightpaths (i.e. stubs) in a cooperative manner. This is achieved by allowing all the failure-aware nodes to switch the traffic, such that the disrupted lightpaths can be protected even if the end nodes of the failed link are not on the protecting cycles. CFP also differs from FIPP p-cycle by not requiring the source node of the disrupted lightpath on the protecting cycle. By jointly optimizing both working and spare capacity placement, we formulate an ILP for CFP design. Numerical results show that CFP significantly outperforms p-cycle by achieving faster protection with much higher capacity efficiency. © 2009 IEEE.published_or_final_versio

An improved tabu-based vector optimal algorithm for design optimizations of electromagnetic devices

Author name used in this publication: S. Y. YangAuthor name used in this publication: S. L. HoAuthor name used in this publication: J. M. MachadoAuthor name used in this publication: Edward W. C. Lo2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe