A Novel Scheduling and Polling Mechanism for Upstream Bandwidth Assignment in a Passive Optical Network

Abstract

In a dynamic bandwidth assignment (DBA) scheme for a passive optical networks (PON), a polling mechanism with higher polling frequency helps OLT to accurately enquire the ONU upstream bandwidth demand. However, due to channel delay, an increase in polling frequency leads to inaccurate bandwidth reporting as the queue reports reach OLT after some delay. This results in inefficient bandwidth reporting (IBR) problem. This IBR problem causes wastage of upstream bandwidth due to inaccurate bandwidth assignment and also leads to higher upstream delays at high traffic loads.This study presents a novel polling and scheduling mechanism which eliminates the IBR problem. In this scheduling mechanism the OLT sends bandwidth allocation for the whole SI period to a TCONT (i) of ONU (i) at once instead of sending it in every downstream frame. A novelpolling mechanism is also presented that subtracts the future grants from the queue reports at the ONUs before sending them to the OLT to combat the channel delay impact. The results obtained through the simulation study show that the proposed scheme improves mean upstream delay by 62% for type 2, 3 and 4 traffic classes compared to EBU and up to 99% compared to IACG DBA scheme.