Traffic-Driven vs. Topology-Driven Strategies for Regeneration Sites Placement
Many studies have been carried out in the field of translucent network design during the last years. Translucent networks use sparse regeneration strategy where electrical regeneration is performed at a limited number of network nodes in order to improve the signal budget. The objective of translucent network design is to judiciously choose the regeneration sites to overcome the signal degradation and to maintain a predefined quality of transmission. Pachnicke et al. have recently proposed an approach for routing and regenerator placement. In this paper, we propose a novel heuristic called COR2P for translucent network design. Our concern is both to minimize the number of required regenerators and to concentrate them in a limited number of sites. In addition, we propose an improved version of Pachnicke's algorithm under the name of RP-CBR+ and we proceed to the comparison of these two approaches. On one hand, both COR2P and RP-CBR+ choose, a priori, a set of regeneration sites, before the effective RWA phase. Our approach is both traffic and topology-driven since it considers the effective traffic matrix and the limited capacity of the network. Oppositely, regeneration sites placement in RP-CBR+ is only topology-driven since it considers a connection demand between any pair of nodes under unlimited network capacity. On the other hand, COR2P differs from RP-CBR+ in three points: the order in which traffic demands are processed, the wavelength assignment strategy and the possibility or not to use additional regeneration sites. Simulation results show that unlike RP-CBR+, COR2P accepts all traffic demands under low traffic load, using the same number of regenerators. Under high traffic load, our algorithm presents much lower blocking ratios than RP-CBR+ at the price of a larger number of regenerators.