New and Improved approaches for Dynamic Bandwidth and Wavelength allocation in LR WDM/TDM PON

Dynamic Bandwidth Allocation is a major open research challenge in the migration of Passive Optical Network (PON) systems towards Long Reach PON, especially when hybrid WDM/TDM is used (LR WDM/TDM PON). New and efficient solutions for Dynamic Bandwidth and Wavelength Assignment are sought to address two main critical issues of such PON systems: how to schedule the transmissions over multiple wavelengths and how to efficiently exploit the bandwidth in presence of the long propagation delays that characterize long reach scenarios. While several DBAs have been proposed for longreach single-wavelength PON system or for WDM/TDM hybrid PONs (with no regard to the long reach aspect), only few DBAs have been investigated in the case of combined LR WDM/TDM PON scenario. Regarding LR TDM PONs, one of the most performing and widely used dynamic allocation schemes is the Multi-thread polling. Although this algorithm has provided good results when applied in these kind of networks, it has never been implemented into a LR WDM/TDM PON. For what concerns this latter network configuration, one of the most straightforward methods for upstream bandwidth and wavelength allocation is the Earliest Finish Time (EFT) algorithm. In this work we implement the Multi-thread polling in a LR WDM/TDM PON providing results in terms of average packet delay. Moreover, we investigate the behaviour of both Multi-thread algorithm implemented in a hybrid WDM/TDM PON and EFT algorithm in different network scenarios where the number of wavelengths changes, in order to evaluate the improvement introduced by the statistical multiplexing. Based on such evaluations, we discuss some possible guideline to efficiently accomodate different types of traffic (e.g., data traffic, voice traffic) in combined structures as Fixed and Mobile converged (FMC) access networks.