The rest of the paper is organized as follows. We introduce the transmission system model consisting of an EH device, a storage unit, and a data buffer in Section \[sec:system\_model\]. We characterize the energy storage performance measures such as energy overflow and energy outage in Section \[sec:Energy\_Storage\_Characterization\]. We provide the throughput analysis in Section \[sec:transmission\_throughput\], i.e., formulate the average data service rate in the channel in Subsection \[sec:reliable\_throughput\] and the effective capacity in Subsection \[sec:effective\_capacity\]. We present the numerical results in Section \[sec:numerical\_results\]. Our conclusions are provided in Section \[sec:conclusion\]. We relegate the proofs to the Appendix.

System Model {#sec:system_model}
============

We consider a discrete-time system model consisting of two separate queues at the transmitter corresponding to the energy and data buffers, respectively. Please, see Fig. \[res:fig\_2\] for an illustration of the system model. We describe each of these components separately.

![EH transmitter model consisting of a data buffer and a battery acting as an energy buffer.[]{data-label="res:fig_2"}](resim_4_new.png){width="55.00000%"}

Energy Harvesting and Storage {#sec:Energy_Harvesting_Storage}
-----------------------------

We denote the amount of the harvested energy in the $i^{\text{th}}$ time frame by $u(i)$ and the amount of energy demanded for data transmission by $p(i)$ for $i=1,2,\cdots$. We assume that $u(i)$ is stochastic and varies from 