Dynamic Bandwidth Allocation with void filling and multi-thread for Long Reach WDM/TDM PONs

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 wave-lengths 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 long-reach 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 promising candidate for upstream bandwidth and wavelength allocation is the Earliest Finish Time with Void Filling (EFT-VF) algorithm. In this work, for the first time, we implement the Multi-thread polling in a LR WDM/TDM PON providing results in terms of average packet delay. Moreover, we propose a new DBWA scheme based on an effective combination of some features of EFT-VF and Multi-thread algorithms, which leads to a performance improvement compared to these algorithms.