A mean value analysis approach for evaluating the performance of EPON with Gated IPACT

The Broadband Passive Optical Network (PON) technology is a promising approach to establish a cost-effective access network. It is intended to provide a simple, low cost, scalable solution capable of delivering broadband access to end users, by passively sharing a single optical fiber transmission system between several packets. While downstream traffic is broadcast to all packets, the access of upstream traffic to the fiber has to be arbitrated in order to avoid collisions. This arbitration mechanism and more generally, bandwidth distribution and QoS Provisioning, have been left to the implementer. Interleaved Polling with Adaptive Cycle Time (IPACT) is one of the earliest proposed schemes for bandwidth distribution in Ethernet PON (EPON) and has been extensively used as a benchmark by many subsequent allocation schemes. In this paper, we propose an analytical model which yields approximate values for mean queue length and mean packet delay in an EPON with the Gated IPACT scheme under the assumption of Poisson arrivals. We show by simulation that the model is remarkably accurate over the whole load range. We use the model to demonstrate that all ONUs experiment performance degradation in case of local overload by some ONUs, thus showing the necessity of correcting somehow the Gated policy in order to avoid this phenomenon.