Simultaneous Wireless Information and Power Transfer in K-Tier Heterogeneous Cellular Networks

In this paper, we develop a tractable model for joint downlink (DL) and uplink (UL) transmission of K-tier heterogeneous cellular networks (HCNs) with simultaneous wireless information and power transfer (SWIPT) for efficient spectrum and energy utilization. In the DL, the mobile users (MUs) with power splitting receiver architecture decode information and harvest energy based on SWIPT. While in the UL, the MUs utilize the harvested energy for information transmission. Since cell association greatly affects the energy harvesting in the DL and the performance of wireless powered HCNs in the UL, we compare the DL and the UL performance of a random MU in HCNs with nearest base station (NBS) cell association to that with maximum received power (MRP) cell association. We first derive the DL average received power for the MU with the NBS and the MRP cell associations. To evaluate the system performance, we then derive the outage probability and the average ergodic rate in the DL and the UL of a random MU in HCNs with the NBS and the MRP cell associations. Our results show that increasing the small cell base station (BS) density, the BS transmit power, the time allocation factor, and the energy conversion efficiency, weakly affect the DL and UL performance of both cell associations. However, the UL performance of both cell associations can be improved by increasing the fraction of the DL received power used for energy harvesting.