Effects of range expansion and interference coordination on capacity and fairness in heterogeneous networks

Range expansion and inter-cell interference coordination can improve the capacity and fairness of heterogeneous networks by off-loading macrocell users to low-power nodes like picocells. In contrast to previous studies, which rely mostly on simulations, we here consider analytical models for base station and user (UE) locations in a macro network with pico-cell overlay and derive closed-form expressions for the distribution of the signal to interference plus noise ratio (SINR) and spectral efficiencies (SEs) of UEs associated with macro- and pico-cells. These results illuminate the effects on SE of (i) duration of the macro almost blank subframes (ABSs), (ii) the SINR threshold for a UE to be served by a picocell during ABSs, and (iii) the range expansion bias. They also help determine the optimum settings of these parameters.