Optical Packet Network With Limited-Range Wavelength Conversion: A Novel Formalization of the Optimal Scheduling Problem

In this paper, we consider synchronous optical packet networks formed by switches equipped with a complete set of limited-range wavelength converters. On these networks, we dealt with scheduling algorithm that maximizes the switch throughput. So far, previous literature works have formalized this scheduling problem as the finding of a maximum bipartite matching (MBM) in a convex graph. The MBM formalization has collected various follow-ups, mainly focused on measuring switch-level performance. We revise the MBM formalization by measuring network-level performance. Surprisingly, we find out that when optical switches are cascaded, MBM formalization has two not negligible lacks: (1) a useless degradation of optical signal quality and (2) a tendency of shifting optical packets toward lower wavelengths, thus increasing the occurrence of wavelength contention. To solve these issues, we propose a novel formalization of the scheduling problem as the finding of a MBM with minimum edges weights (MW-MBM). We show that MW-MBM outperforms MBM in terms of both network throughput and optical SNR. Performance evaluation is carried out by means of NS2 simulator that we extend to toughly model optical components (e.g., semiconductor optical amplifier four-wave-mixing wavelength converter). The simulator is provided as open source.