Adaptive scheduling for differentiated services in an Ethernet passive optical network

Feature Issue on Optical Access Networks (OAN) The Ethernet passive optical network (EPON) is a technology viewed as an attractive solution to the "last mile" problem. The interleaved polling with adaptive cycle time (IPACT) is a remarkable medium access control (MAC) protocol for EPONs. The IPACT scheme supports two stages of scheduling. One is inter-optical network unit (ONU) scheduling. The other is intra-ONU scheduling. In this paper, we propose a systematic adaptive scheduling scheme to enhance the functions of the IPACT on both types of scheduling in order to achieve efficient bandwidth utilization of EPONs under unbalanced traffic and to provide class-of-service (COS) or differentiated services within an ONU. The simulation results show that our proposed scheduling scheme can improve the performance of the EPON system under unbalanced traffic loads and provide fair bandwidth allocation of the uplink to different types of traffic.