Multiuser communications with energy harvesting transmitters

This paper considers a communication system composed of multiple transmitter-receiver pairs (users) that must share the same frequency band. As battery replacement may be a tedious task, transmitters are solely powered by energy harvesters, specifically, by solar and electromagnetic energies. In previous works for non-harvesting nodes, transmissions of other nodes limit the achievable rate of a certain user due to interference. In contrast, when a certain transmitter harvests electromagnetic energy, transmissions of other nodes may be beneficial as part of the transmitted energy can be harvested and later used to increase the transmission power and, accordingly, the achievable rate. In this context, this paper formulates a Nash Equilibrium (NE) problem with prices to assign the transmission powers of the different nodes by taking into account constraints in the transmission power and the Energy Causality Constraints (ECCs), which intrinsically couple the different user transmission strategies. The existence and uniqueness of the equilibrium are characterized by using the theory of finite dimensional Variational Inequalities (VIs).