Esnek optik ağlarda adaptif modülasyon ve kodlama ile yenileyici yerleştirilmesi

Due to the rapid and diverse increase in the traffic load on the optical networks, efficient utilization of the network resources becomes an important issue. Using different modulation formats and coding rates in optical signal transmission, it is possible to assign different spectral efficiency and optical reach for each traffic requests. To satisfy the quality of transmission (QoT) for the distances beyond optical reach, optical - electronic - optical (O/E/O) 3R regeneration of the optical signal is required. During the regeneration process, the spectral efficiency and thus optical reach of the resultant signal can also be set. In these circumstances, by selecting specific regenerator node locations and assigning different line rates for each traffic request, the network utilization can be optimized. Joint selection of regenerator placement (RP), routing and adaptive modulation and coding (AMC) profile in elastic optical networks (EON) is studied to propose an offline RP algorithm for a given network topology with link length and link capacity constraints. For a given RP, an Integer Linear Programming (ILP) model is formulated to perform routing and AMC profile assignment for each traffic demand. We use two different approaches for determining candidate paths for routing: In the first set, k shortest paths (KSP) are utilized for all cases. In the second set, namely regenerator location dependent path selection (RLDPS), the candidate paths are determined according to the given RP. To find the minimum cost RP among all possibilities, Tabu Search based regenerator placement algorithm (TSRPA) is proposed. Results show that adaptively selecting the candidate paths based on the regenerator locations reduces network utilization either by decreasing the number of regenerator nodes by up to 66.6% or decreasing link capacity utilization by up to 5.09% as compared to selecting candidate paths as fixed k shortest paths. The regenerator node location distribution obtained with RLDPS concentrated on smaller number of nodes compared to the results obtained with KSP. By placing regenerators at a significantly less number of nodes, capital expenditures (CAPEX) are reduced by RLDPS.