Will caching at base station improve energy efficiency of downlink transmission?

Caching popular contents at the base station (BS) can reduce the end-to-end delay of service and the cost of cellular networks. Yet it is unknown whether introducing cache to BS can improve the energy efficiency (EE) of downlink systems. With BS caching, energy consumption for backhauling can be reduced, but caches will also consume energy. In this paper, we analyze the EE of two kinds of networks with a macro BS or multiple non-coordinated pico BSs with caches, where the impact of content popularity and request arrival density are considered. Analytical and simulation results show that introducing cache can improve the EE if the file catalog size is not too large and placing the caches at the pico BSs is more energy efficient.