Incorporating Coding To Formulate Multicast Sessions In Elastic Optical Networks

Elastic Optical Networks (EONs), which are based on the optical-orthogonal frequency division multiplexing (O-OFDM) technology, are rapidly developed. Compared with the traditional fixed-grid wavelength-division multiplexing (WDM) networks, EONs use contigious frequency slots to assign spectrum resourse, and can achieve the bandwidth allocation granularity at 12.5 GHz or less. Hence EONs provide enhanced spectral efficiency and make the spectrum allocaton in the optical layer more flexible. Besides these advantages, EONs also bring new challenges to the network control and management (NC&M). Specifically, to establish a lightpath in an EON, the network operator needs to allocate a few spectrally-contiguous frequency slots (FS-) to satisfy the bandwidth demand. Here, the bandwidth of an FS is usually at 12.5 GHz, which is much narrower than a wavelength channel. Moreover, since we consider all-optical multicast without spectrum conversions, the modulation format and spectrum assignment stay unchanged for all the links on a light-tree.In this paper, we study the multicast-capable routing, modulation, and spectrum assignment (MC-RMSA) schemes that consider the physical impairments from both the transmission and light splitting in elastic optical networks (EONs). In this paper, we study the optical multicast problem in two different scenarios:allowing optical-electrical-optical (O/E/O) conversion and transparent optical networks. Specifically, we propose to provision each multicast request with a light forest, which consists of one or more light trees to avoid the dilemma that because of the accumulated physical impairments, a relatively large light tree may have to use the lowest modulation level, and, hence, consume too many frequency slots (FS’).On the first scenario, we firstly use Set-Cover approach to get subsets of destinations, then we use network coding approach to get the light-trees. We evaluate the algorithms in simulations of dynamic network provisioning and the results demonstrate that our approaches can achieve better performance on blocking probability than the existing algorithms.On the second scenario, in order to further improve the spectral efficiency and compensate for the differential delays among the light trees, we incorporate the rateless network coding (R-NC) in the multicast system. We first formulate an integer linear programming model to solve the problem for static network planning. Then, we propose three time-efficient heuristics that leverage the set-cover problem and utilize layered auxiliary graphs. The simulation results indicate that in both the integer linear programming and heuristics, the MC-RMSA with R-NC can achieve better performance on the maximum index of used FS’than that without. After that we evaluate the heuristics in a dynamic network provisioning. The results show that the MC-RMSA with R-NC can effectively improve the performance of all-optical multicast in EONs to reduce the blocking probability.