The popularity of Energy Harvesting Devices (EHDs) has grown in the past few
years, thanks to their capability of prolonging the network lifetime. In
reality, EHDs are affected by several inefficiencies, e.g., energy leakage,
battery degradation or storage losses. In this work we consider an energy
harvesting transmitter with storage inefficiencies. In particular, we assume
that when new energy has to be stored in the battery, part of this is wasted
and the losses depend upon the current state of charge of the device. This is a
practical realistic assumption, e.g., for a capacitor, that changes the
structure of the optimal transmission policy. We analyze the throughput
maximization problem with a dynamic programming approach and prove that, given
the battery status and the channel gain, the optimal transmission policy is
deterministic. We derive numerical results for the energy losses in a capacitor
and show the presence of a \emph{loop effect} that degrades the system
performance if the optimal policy is not considered.Comment: In Proc. IEEE Twelfth Int. Symposium on Wireless Communication
Systems (ISWCS), pp. 406-410, Aug. 201
