A Fitting Report Position Scheme for the Gated IPACT Dynamic Bandwidth Algorithm in EPONs

In EPONs using the gated Interleaved Polling with Adaptive Cycle Time (IPACT) scheme, the position of the report message within the granted transmission window has a direct effect on the average packet delay within the network. In this paper, this delay is minimized by using a fitting report position (FRP) scheme to adaptively adjust the position of the report message within the transmission window in accordance with the current network load. In the proposed approach, the optimal position of the report message is determined analytically for various system loads. The optical line terminal (OLT) then uses a heuristic algorithm to estimate the load of the optical network units (ONUs) in accordance with their report messages and determines the report message position that minimizes the average packet delay within the network. Finally, the OLT informs the ONUs of the optimal report position through an optional field in the gate message. The performance of the proposed FRP scheme is evaluated for three different network models, namely Poisson traffic with a uniform ONU load, Poisson traffic with a nonuniform ONU load, and self-similar traffic, respectively. The simulation results show that the FRP scheme achieves a lower average packet delay than fixed-report-position schemes such as fixed-report-front (FRF) or fixed-report-end (FRE) for both Poisson and self-similar traffic. The performance improvement is particularly apparent in networks with a nonuniform ONU load distribution.