To Mute or to Whisper: A Study on Low-Duty Mode Operation for Interference Control in HetNets

Time-domain interference control such as the low duty mode (LDM) operation in IEEE 802.16m and almost blank sub frame (ABS) in LTE-A has been proposed as an alternative for enhanced interference mitigation in femto cells. Through controlling the on/off durations of interfering femto BSs in the time domain, interference can be properly mitigated or even avoided without invoking fine-grained power control at individual femto BSs. In this paper, we investigate the performance tradeoffs of time-domain and power-domain interference control for heterogeneous networks. By focusing on the LDM instantiation, we first formulate a network optimization problem that takes into consideration the service requirements of macro and femto users with the objective of deciding the optimal LDM patterns among a set of femto BSs. To solve the formulated problem, we transform the problem into a form with lower complexity that can be solved using existing solvers. Simulation results show that time-domain interference control based on LDM outperforms conventional schemes based on transmission power control.