A Blocking Analysis for Green WDM Networks with Transponder Power Management

Energy-efficiency has become a hot topic in the field of optical Wavelength Division Multiplexing (WDM) networks. Various energy-efficient network-resource management schemes have been proposed in the last few years. A very promising strategy consists on putting unused transponders into a low- power state, called idle or sleep state, or even turning them off. However, in such scenario, it is of capital importance to guarantee that high-priority services, which require low set-up times, are quickly established without waiting for the long activation of powered-off devices. On the other hand, other services that may not require such strict set-up times, can wait until a powered-off device is activated. A possible strategy to fulfill such requirements is to reserve some idle transponders for high priority connections. In this paper we present a novel Markov chain-based analytical model to evaluate the power savings and the blocking probability of such strategy. The presented model can serve to forecast both power savings and blocking levels in a network scenario and give hints on how to dimension the number of reserved devices for high priority traffic depending on the number of wavelengths per link, the wake-up time of the transponders and the network load.