Interference mitigation in two-tier LTE networks: Does power control pay off for femtocells?

Femtocell networks have emerged as an important means of offloading traffic from today's LTE cellular networks. However, deploying LTE femtocells increases the interference in the network, as they share licensed spectrum with the macro-cellular network. Consequently, a wide range of interference mitigation techniques have been proposed to enable coexistence of femtocells and macrocells. Techniques of various implementation and signaling complexity have been considered, but the majority of existing work evaluates their performance solely based on how well they mitigate interference for macrocell users. However, it is important that both macrocell and femtocell users achieve good performance. In this paper we present a comparative system-level study on the performance of several LTE femtocell frequency and power allocation schemes. We investigate whether more complex and dynamic resource allocation schemes, i.e. power control, are worthwhile from the point of view of femtocell networks compared to lower complexity static resource allocation schemes. We evaluate the performance in terms of the users' downlink throughput and achieved signal-to-interference-plus-noise ratio (SINR), and we consider different interference environments for a wide range of network densities (urban, suburban, and rural scenarios). Our results show that power control algorithms only yield a marginal increase in throughput for the LTE femtocell users. This suggests that increasing the complexity of static frequency allocation schemes by implementing power control algorithms is not justified.