WDM star subnetwork upgrade of optical ring networks for maximum spatial reuse under multicast traffic

We examine a recently proposed multichannel upgrade of optical single-channel ring networks where a subset of ring nodes is WDM upgraded and interconnected by a single-hop star WDM subnetwork in a pay-as-you-grow fashion. This evolutionary approach not only allows for fast and efficient multiple-failure recovery but also is well suited to efficiently sustain unpredictable changes and shifts in traffic loads. In this paper, we analytically investigate the maximum achievable capacity of the WDM star subnetwork upgrade of optical single-channel networks under a variety of unicast and multicast traffic scenarios and compare it to that of conventional WDM ring networks. In our analysis, we take priority of ring in-transit traffic, destination stripping, and maximum spatial reuse into account. Our findings show that under multicast traffic the configuration of the star subnetwork plays an important role in order to achieve high multicast capacity. Furthermore, under multicast traffic WDM upgrading and interconnecting a subset of ring nodes might be sufficient to achieve a larger multicast capacity than in WDM rings