Multi-flow virtual concatenation triggered by path cascading degree in Flexi-Grid optical networks

The Flexi-Grid optical networks can elastically allocate spectrum tailored for various bandwidth requirements. In the flexible architecture, routing and spectrum allocation (RSA) is the key problem is to assign spectral resources to accommodate traffic demands. However, spectrum continuity and contiguity constraints in Flexi-Grid optical networks may cause the network fragmentation issue and lead to poor spectrum utilization. In this paper, different from defragmentation methods, we propose multi-flow virtual concatenation (MFVC) in Flexi-Grid optical networks. MFVC can utilize spectral fragments effectively and decrease blocking probability without influencing the already existing active services or wasting additional spectrum resources. We also analyze the feasibility of MFVC and present a MFVC-enabled transponder and control model implementation. For estimating the distribution and size of available fragments on a path in advance, a split-multi-flow RSA heuristic algorithm (SMF) is proposed by introducing path cascading degree (PCD) based triggered mechanism according to the proposed model. Additionally, resource assignment scheme, guard band size, maximum number of split-flow and differential delay constraint are also considered into MFVC and the performances of the proposed algorithm can be demonstrated to improve the spectral utilization and greatly decrease blocking probability through extensive simulations.