A Blocking Analysis for Green WDM Networks with Transponder Power Management

Providing energy-efficiency in optical Wavelength Division Multiplexing (WDM) networks has become crucial in the last few years. One option, which is largely assumed in many recent research studies, consists of setting unused net- work devices into low-power sleep-mode or, eventually, turn- ing them off. In this scenario, fast configuration of idle re- sources must be taken into account, since some high-priority services, especially real-time ones, need to be assigned to network resources as soon as they require them. Therefore, it is possible to reserve some resources (e.g., WDM trans- ponders) for those connections with high Quality of Service (QoS) requirements, in terms of speed of connection set-up. Some other connections, e.g., file-transfer, e-mail etc., may not have such strict constraint, so that they can wait until a powered-off transponder is activated and made available. Therefore we could identify two (or more) classes of connec- tions, namely High-priority and Low-priority connections. In this paper we provide an analytical blocking model to evaluate the performance, i.e., the energy-benefit and block- ing ratio, of such a scenario, where some of the unused net- work devices (transponders) can be set into sleep-mode and reserved for High-priority connections, whereas the other un- used transponders, are still maintained as powered-off. We find that substantial energy savings, on the order of 60%, can be obtained with such management strategy, with an acceptable degradation in the overall network blocking per- formance.