Abstract
In this work, we develop an analytical framework to evaluate the network throughput and energy efficiency in heterogeneous cellular networks (HCNs) with multiple energy harvesting cells. The network consists of a tier of power-grid connected base stations (BSs) and multiple tiers of energy harvesting small cell access points (EH-SAPs). Specifically, we derive the rate coverage after modeling the battery energy dynamic using discrete time Markov chain for energy harvesting (EH)-small cell access points (SAPs) according to an arbitrary transmission power. We then derive the network throughput and the energy efficiency by taking account for the energy harvesting probability, cell association bias, and the transmission power of EH-SAPs. We also explore the optimal transmission power of EH-SAPs and cell association bias in terms of the throughput and the energy efficiency. We show that offloading all traffic of the network to EH-SAPs can enhance the network throughput also the energy efficiency, especially when the transmission power of EH-SAPs is low. Moreover, lower transmission power of EH-SAPs can achieve higher network throughput, but the optimal transmission power of EH-SAPs in terms of network energy efficiency generally increases with the density of EH-SAPs. This research offers insights on the design of spectral- and energy-efficient heterogeneous network including the effects of cell association bias, SAP density, and transmission power of EH-SAP on the network performance.