Cluster-based PON with dynamic upstream data transmission sequence algorithm for improving QoSs

Abstract

Passive optical network (PON) with online polling-based dynamic bandwidth allocation (DBA) algorithms effectively reduces the granting and back-off delays as well as the overall end-to-end delay of the PON with offline polling-based DBA schemes. However, in the online polling-based DBA schemes, distribution of excess bandwidths from the lightly loaded optical network units (ONUs) to the highly loaded ONUs is not possible. In both the conventional online and offline polling-based DBA schemes, theoptical line terminal (OLT) assigns the time-slots to the ONUs for upstream data transmissions based on the first-come-first-serve principle. That is why the highly loaded ONUs those remainbehind the lightly loaded ONUs should be waited until the end of the upstream data transmissions of all the preceding ONUs. Due to this longer waiting time before getting the chance to transmit the upstream data increases the possibility of buffer overflow of the highly loaded ONUs. In this paper, a new cluster-based PON architecture with a dynamic upstream data transmission sequence (DUDTS) algorithm is introduced. In the cluster-based PON with DUDTS scheme, all the active ONUs of a PON system are divided into several clusters. Then the data transmission sequence of the ONUs in each cluster is dynamically changed to give higher priority to the highly loaded ONUs for assigning the earlier time-slots than the lightly loaded ONUs. The DUDTS scheme also considers the traffic incoming statuses in the ONUs’ buffer,distributes the excess bandwidth from the lightly loaded ONUs to the highly loaded ONUs within a cluster, and adds the unutilized bandwidth of a cluster to the ONUs of thefollowing cluster. Numerical simulations are performed to evaluate and compare the performances among the proposed cluster-based PON with DUDTS scheme and the existing dynamic hybrid slot-size bandwidth allocation (DHSSBA) algorithm to demonstrate the effectiveness of the proposed scheme. The cluster-based PON with DUDTS scheme provides better results in terms of the grant to request ratio, end-to-end delay, packet loss probability, and fairness compared to the existing DHSSBA scheme.