Performance analysis of passive optical networks with energy saving through the integrated sleep mode

Improving the energy efficiency has become an important aspect of designing optical access networks to minimize their carbon footprints. In this context, interleaved polling with adaptive cycle time (IPACT) with the integrated sleep mode is considered as a medium access control (MAC) scheme to improve the energy efficiency of passive optical networks (PONs). The decision criterion for energy saving is to put an ONU in the sleep mode when no upstream and downstream traffic exists, without impairing the desired quality of service (QoS) requirements in terms of the mean packet delays. We derive approximated and conservative closed form expressions of the upstream and downstream mean packet delays for the integrated sleep mode by modeling a PON as an N-user M/G/1 queue with reservations and vacations. Simulation experiments are conducted to validate the need of joint consideration of upstream and downstream traffic to avoid excessive delays in packet transmissions. Simulation experiments also validate the analytical results and show that the mean packet delays are relatively insensitive to packet arrival statistics for large sleep periods. Hence, our analytical results may also be applied to more practical scenarios with non-Poisson packet arrivals.