Power saving clusters for energy-efficient design of fiber-wireless access networks

Wireless and optical broadband access technologies are foreseen to converge by combining the high transmission capacity of the optical communications with the flexibility and the ubiquitous nature of the wireless communications in order to satisfy the growing end-user demand for bandwidth. This hybrid technology eliminates the cost of running fiber to the destination by allowing the fiber deployment until a certain point from where wireless base stations take over to provide service to the end-user. Despite handling the growing end-user demand, new telecommunication technologies are required to be energy efficient. Recently, there is an increasing interest to reduce the energy consumption of the Information and Communications Technology (ICT) sector and the ICT related CO2 emissions. In this paper, we propose an energy efficient design scheme for a fiber-wireless network consisting of a WDM-PON in the optical back-end and a 4G broadband access technology-enabled wireless front-end, e.g. Long-Term Evolution (LTE) or WIMAX. The proposed design scheme uses the average load profiles on the WDM-PON segments and attempts to form power saving clusters (PSCs) which are fiber rings interconnecting several hybrid (fiber-wireless) access networks. Each PSC enables one or more OLTs to sleep and distributes the backlogged traffic among the active segments in the ring. The proposed scheme aims to maximize the number of sleeping segments, and consequently maximize the power saving. Through simulations, we show that the proposed scheme leads to a power saving between 20% and 45% with a maximum of 3.5% increase in the fiber deployment cost by running the interconnection fibers to form PSCs.