A Blocking Analysis for Green WDM Networks With Transponder Power Management

Energy-efficiency has been widely recognized as an important target in the management of optical wavelength division multiplexing networks. A very promising power management strategy consists in putting unused transponders into a low-power state, called idle or sleep state, or even in turning them off. However, in such scenario, it should be also guaranteed that high-priority traffic, which requires short setup times, is quickly established without waiting for the long activation time of powered-off devices. A possible strategy to avoid long setup times is to reserve some idle transponders for high-priority traffic. However, reserving a large number of idle transponders for high-priority traffic will increase the blocking of low-priority traffic, since less resources are available. To analyze this tradeoff, in this paper we present a novel analytical model based on Markov chains to evaluate the blocking probability and the power savings of this transponder power management in presence of high- and low-priority traffic. The presented model can be used to estimate both power savings and blocking levels and to provide guidelines on how to dimension the number of reserved devices for high-priority traffic.