A Study on Impacts of RTT Inaccuracy on Dynamic Bandwidth Allocation in PON and Solution

TL;DR

This paper investigates how inaccuracies in RTT estimation affect dynamic bandwidth allocation in PON systems, analyzing performance impacts and proposing solutions to mitigate bandwidth wastage and collisions.

Contribution

It evaluates the effects of RTT inaccuracy on DBA performance and introduces a method to improve bandwidth allocation accuracy in PON networks.

Findings

RTT inaccuracy causes increased bandwidth collisions.

Bandwidth waste increases with RTT estimation errors.

Proposed method reduces performance degradation due to RTT errors.

Abstract

The circle travelling delay between OLT (Optical Line Terminal) and ONU (Optical Network Unit) is one of most important items in dynamic bandwidth allocation (DBA) algorithms in PON, called RTT (Round Trip Time). The RTT is taken into account when OLT assigns the start times for upstream bandwidth grants. In most case, RTT is estimated before making bandwidth allocation decisions in dynamic bandwidth allocation algorithms. If the estimated RTT is incorrect, the bandwidth allocation decisions are not matched with bandwidth requests of channels. Thus, performance of PON can get worse by deviation of RTT. There are several reasons that cause the RTT to be varying, such as processing delay, distance of OLT and ONU, changing in fiber refractive index resulting from temperature drift, and degree of accuracy of RTT estimation methods. In this paper, we evaluate the impacts of RTT inaccuracy on performance of DBA and identify levels of collision and waste of bandwidth. By this way, we propose a method to remedy the performance degradation encountered by the situation