Towards a fair and efficient downlink bandwidth distribution in XG-PON frameworks

Fairness assurance in modern access networks constitutes a focal point of interest since it dramatically affects the quality of the provided services to the final users. Traffic balancing entails fair bandwidth distribution along with efficient service provisioning, inaugurating a challenging tradeoff between the system throughput and fairness. In this paper, the downlink scheduling effectiveness in modern passive optical networks (PONs) is examined, adopting the ten-gigabit passive optical network (XG-PON) architecture deployed in a tree topology. Considering that the tree topology implies a broadcast nature of data delivering in the downlink direction, the tradeoff between the efficiency and fairness becomes even more compelling, bearing in mind that the distance the broadcast data propagate between the source and users' destination is highly differentiated. In order to remedy this situation two effective scheduling schemes are proposed, namely the shortest propagation processing time (SPPT) and the shortest weighted propagation processing time (SWPPT). Both algorithms are extensively assessed, while the obtained results indicate that the proposed algorithms assure a fair and effective downlink schedule.