Y. Chen

University of Windsor, Windsor, Ontario, Canada

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Publications (8)0.33 Total impact

  • Y. Chen, A. Bari, A. Jaekel
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    ABSTRACT: The need for powerful computing resources as well as capabilities for storage and transmission of large amounts of data in a number of application areas have led to the emergence of optical grids as a natural, cost-effective platform for supporting such applications. As a result there is also an increasing need for strategies and techniques designed to achieve fault tolerance in optical grid networks. Design for fault tolerance in both grid computing and optical networks are mature, well-researched fields in their own right. However, survivability in optical grids should not be treated merely as a concatenation of techniques developed separately in these two disciplines. Rather, it would be beneficial, in terms of resource availability as well as cost-effectiveness, to develop an integrated approach that takes into consideration the allocation of both computing and networking resources jointly. In this paper, we review the state-of-the-art techniques and approaches that have been proposed in the literature, for designing survivable optical grid networks. We also discuss some challenges, identify some open problems and outline future research directions for developing an integrated approach to fault tolerance in optical grids.
    01/2012;
  • A. Jaekel, Y. Chen
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    ABSTRACT: Multifibre optical networks use a bundle of fibres to realize a link between two optical nodes. Such networks can offer significant economic benefits over single-fibre networks because of their ability to relax the restrictions imposed by the wavelength continuity constraint and their potential for handling future growth. This paper introduces two new and efficient integer linear program (ILP) formulations for dynamic wavelength allocation in survivable multifibre wavelength-division multiplexing (WDM) networks, using dedicated and shared protection. Single-fibre networks, both with and without wavelength conversion, can be treated as a special case of these formulations. The new formulations have been tested on several well-known WDM networks, and the results have been compared to those for single-fibre networks. A simple heuristic for dynamic lightpath allocation is also proposed, and its performance is validated by a comparison of the results to optimal solutions generated by the ILPs. Experimental results demonstrate that the new ILPs are feasible for current networks under low-to-medium traffic. For very large or highly congested networks, the heuristic can be used.
    Canadian Journal of Electrical and Computer Engineering 02/2008; · 0.33 Impact Factor
  • A. Jaekel, Y. Chen
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    ABSTRACT: It has been shown that for the scheduled traffic model, connection holding time aware algorithms lead to more efficient resource allocation. The setup and teardown times of the scheduled demands may be fixed, or may be allowed to slide within a larger window. A number of optimal integer linear program (ILP) solutions for the first problem (fixed setup/teardown times) have been presented in the literature, for wavelength convertible networks. In this paper we present a new and complete ILP formulation for both fixed window model, and the more general sliding scheduled traffic model, where the setup and teardown times may vary within a specified range. We consider fault-free as well as survivable networks using path protection, and do not require any wavelength conversion. Our ILP can jointly optimize the problem of scheduling the demands (in time) and allocating resources for the scheduled lightpaths. We have shown that the complexity of our formulation for sliding scheduled traffic model, in terms of the number of integer variables, is less than existing ILP formulations for the simpler fixed window model. For very large networks, we have proposed a fast two-step optimization process. The first step schedules the demands optimally in time, such that the amount of overlap is minimized. The second step uses a connection holding time aware heuristic to perform routing and wavelength assignment for the scheduled demands.
    Broadband Communications, Networks and Systems, 2007. BROADNETS 2007. Fourth International Conference on; 10/2007
  • A. Jaekel, Y. Chen
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    ABSTRACT: In this paper, we consider resource allocation under the scheduled traffic model, where the setup and teardown times of scheduled demands are known in advance. A number of integer linear program (ILP) solutions for this problem have been presented in the literature. Most of these ILPs minimize the number of wavelength links. A more appropriate metric, for wavelength routed, all-optical networks, is to minimize the congestion (the maximum number of lightpaths on a single fiber link) of the network. We present a new ILP formulation for routing and wavelength allocation, under the scheduled traffic model that minimizes the congestion of the network. We propose two levels of service, where idle backup resources can be used to carry low-priority traffic, under fault-free conditions. When a fault occurs, and resources for a backup path need to be reclaimed, any low-priority traffic on the affected channels is dropped. The results demonstrate that this can lead to significant improvements over single service level models. We also show that the complexity of our formulation (in terms of the number of integer variables) is lower, even compared to existing approaches, which only allow a single level of service. Therefore, we are able to generate optimal solutions for practical networks within a reasonable amount of time, whereas existing formulations often do not find the optimal solution even after 2 h. Finally, we present a simple and fast heuristic that can quickly generate good solutions for much larger networks.
    Computer Communications. 01/2007;
  • A. Jaekel, Y. Chen
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    ABSTRACT: The deployment of multifiber, wavelength division multiplexing (WDM) networks can offer significant economic benefits over single fiber networks, because of their ability to relax the restrictions due to the wavelength continuity constraint and the potential to handle future growth. In this paper we introduce a new integer linear program (ILP) formulation for dynamic wavelength allocation in survivable, multifiber WDM networks. Single fiber networks, both with and without wavelength conversion, can be treated as a special case of our formulation. We have tested our formulations on several well- known WDM networks and compared the results to single fiber networks. We have also proposed a simple heuristic for dynamic lightpath allocation. Experimental results demonstrate our ILP formulation is feasible for current networks under low to medium traffic. For very large or highly congested networks, the heuristic can be used.
    Broadband Communications, Networks and Systems, 2006. BROADNETS 2006. 3rd International Conference on; 11/2006
  • A. Jaekel, Y. Chen
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    ABSTRACT: In the scheduled traffic model, the design problem is to allocate resources to a set of demands whose setup and teardown times are known in advance. A number of integer linear program (ILP) solutions for this problem have been presented in the literature. In this paper we present a new ILP formulation for routing and wavelength allocation, under the scheduled traffic model that minimizes the congestion of the network. We propose two levels of service, where idle backup resources can be used to carry low priority traffic, under fault-free conditions. When a fault occurs, and resources for a backup path need to be reclaimed, any low priority traffic on the affected channels is dropped. The results demonstrate that this can lead to significant improvements over single service level models. We are able to generate optimal solutions for moderate sized networks, within a reasonable amount of time. Finally, we present a simple and fast heuristic that can quickly generate good solutions for much larger networks.
    Broadband Communications, Networks and Systems, 2006. BROADNETS 2006. 3rd International Conference on; 11/2006
  • A. Jaekel, Y. Chen
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    ABSTRACT: There has been considerable research interest in the use of path protection techniques for the design of survivable WDM networks. In this paper, we present a distributed algorithm for dynamic lightpath allocation, using both dedicated and shared path protection. The objective is to minimize the amount of resources (wavelength-links) needed to accommodate the new connection. We have tested our algorithms on a number of well-known networks and compared their performance to “optimal” solutions generated by ILPs. Experimental results show that our algorithm generates solutions that are comparable to the optimal, but are significantly faster and more scalable than corresponding ILP formulations.
    12/2005: pages 189-194;