Modeling and optimizing the delay-energy tradeoff in TDM systems with sleep mode

Abstract

Power consumption in access networks is becoming a relevant issue. Strategies for reducing the power consumption (such as sleep mode support) and enhancing the energy proportionality have been recently proposed and also introduced in the standards for access networks based on time division multiplexing (TDM).This paper aims to model the power dissipation and the performance of a generic TDM transmission system, enabled with energy efficiency strategies, i.e., support of sleep mode and energy proportional devices. Cyclic sleep is considered, i.e., sleep periods are fixed and periodic on a time frame basis. The average power dissipation is exactly derived by accounting the power consumed in the active, idle, and sleep state. The system performance is accurately modeled in terms of delay experienced by the data packets, by using an approximate queueing theory approach.Sleep mode is proved to be effective -especially at low loadsfor reducing the power consumption, but not for improving the energy proportionality of the overall system. Additionally, sleep mode increases the average delay experienced by the packets. The optimal tradeoff between the contrasting performance is found by resorting to the definition of the delay energy metric. Finally, the results indicate that the energy proportional strategies are suitable for reducing the power consumption at medium and low loads, without affecting the delay performance.Index Terms-TDM systems and networks, sleep mode, energy proportionality, queueing model.