Abstract-In this paper, we focus on reducing the on-grid energy consumption in Heterogeneous Radio Access Networks (HetNets) supplied with hybrid power sources (grid and renewables). The energy efficiency problem is analyzed over both short-and long-timescales by means of reactive and proactive management strategies. For short-timescale case, a renewable-energy aware User Equipment (UE)-Base Station (BS) association is proposed and analyzed for the cases when no storage infrastructure is available. For long-timescale case, a traffic flow method is proposed for load balancing in renewable energy BSs, which is combined with a model predictive controller (MPC) to include forecast capabilities of the renewable energy source behavior in order to better exploit a Green HetNet with storage support. The mechanisms are evaluated with data of solar measurements from the region of Valle de Aburrá, Medellín, Colombia and wind estimations from the Moscow region, Russian Federation. Results show how the green association proposal can reduce ongrid energy consumption in a HetNet by up to 34%, while is able to exceed the savings obtained by other methods, including the best-signal level policy by up to 15%, additionally providing high network efficiency and low computational complexity. For the long-timescale case, MPC attainable savings can be up to 22% with respect to the on-grid only Macro-BS approach. Finally, an analysis of our proposals in a common scenario is included, which highlights the relevance of storage management, although emphasizing the importance of combining reactive and proactive methods in a common framework to exploit the best of each approach.

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During the study of some decay processes in marble covering the façade of the Florence Cathedral (1870-1887), vaterite was found as the principal component of some bonding mortars of inlay decorations.Vaterite is one of the three polymorphous phases of CaCO3 and crystallizes in the hexagonal system, dihexagonal bipyramidal class (Kamhi, 1963; Sato and Matsuda, 1969): it is unstable under normal environmental conditions (Deer et al., 1964).

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Previous research has shown the relationship between the number of users connected to a cellular network base station (BS) and its energy consumption. For this reason, the study of optimal mechanisms that balance the load of users over the available BSs is a key element in the field of energy efficiency in cellular networks. The target of this paper is to propose and assess different user–BS association mechanisms to reduce grid consumption in heterogeneous cellular networks powered by hybrid energy sources (grid and renewable energy). These schemes are compared with the traditional best‐signal‐level mechanism and evaluated via simulation by using key performance indicators related to grid consumption, number of users served, and average transmission rate per user. Our results show that the new proposed user allocation policies improve grid electricity consumption while reducing unserved users compared with the traditional association scheme.

In this paper, the user-base station (BS) association problem is addressed to reduce grid consumption in heterogeneous cellular networks (HetNets) powered by hybrid energy sources (grid and renewable energy). The paper proposes a novel distributed control scheme inspired by population games and designed considering both atomicity and non-anonymity -i.e., describing the individual decisions of each agent. The controller performance is considered from an energy-efficiency perspective, which requires the guarantee of appropriate qualityof-service (QoS) levels according to renewable energy availability. The efficiency of the proposed scheme is compared with other heuristic and optimal alternatives in two simulation scenarios. Simulation results show that the proposed approach inspired by population games reduces grid consumption by 12% when compared to the traditional best-signal-level association policy.

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