Reconfiguration of Sub-Wavelength Groomed Wavelength Routed Optical Networks

Abstract

Telecommunication networks recently have seen a large increase in traffic demands, especially data traffic as compared to voice traffic. With the advances in fiber optics and wavelength division multiplexing (WDM), optical networking is the key to satisfy the data-driven bandwidth demand. These technologies enable simultaneous transmission of signals on separate high-speed channels at different wavelengths. While current technologies can provide such huge bandwidth, in order to utilize efficiently the capacity of each lightpath, a number of independent lower-rate traffic streams must be multiplexed into a single lightpath. This technique is referred to as traffic grooming. Another most attractive feature of WDM and wavelength routing networks is the possibility of adaptively creating virtual topologies, or a set of lightpaths, based on network need, giving rise to the concept of reconfiguration. Till date, however, there has been little or no work on the joint consideration of the two areas of traffic grooming and reconfiguration, even though it is clear that reconfiguration is at least equally important in the realistic networks of tomorrow which will definitely need to carry sub-wavelength traffic. This is probably due to two reasons: the common wisdom has been that the two aspects can be handled separately, and also it is hard to define reasonable network design goals if the two aspects are considered jointly. In this thesis, we examine this issue of reconfiguration in groomed networks. The overall focus of this work has been the balancing of the reconfiguration cost and a good grooming solution. We define suitable goals for an integrated approach, and provide formulation of the integrated approach as an integer linear program. To allow a joint consideration of grooming and reconfiguration costs, we mathematically formulate a representation of the reconfiguration cost in terms of the OXC and DXC reconfiguration that can be related to grooming costs. We also develop a heuristic strategy for addressing the problem, which attempts to achieve minimal disturbance reconfiguration by performing local reconfiguration and delaying the need for global reconfiguration. In order to proactively avoid global reconfiguration, we introduce the concept of over provisioning at the traffic demand level. Our reconfiguration heuristic minimizes the need for solving the integer linear program, which is computationally intractable. We also present numerical results validating our claims.