Spectrum Allocation for ICIC-Based Picocell

In this paper, we analytically study the impact of spectrum-allocation scheme in picocells on the coverage probability (CP) of the pico user (PU) when the macro base stations (MBSs) employ either fractional frequency reuse (FFR) or soft frequency reuse (SFR). Assuming a fixed size for the picocell, the CP expression is derived for a PU present in either a FFR- or a SFR-based deployment and when the PU uses either the center or the edge frequency resources. Based on these expressions, we propose two possible frequency-allocation schemes for the picocell when FFR is employed by the macrocell. The CP and the average rate expressions for both schemes are derived, and it is shown that these schemes outperform the conventional scheme where no intercell interference coordination is assumed. The impact of both schemes on the macro-user performance is also analyzed. When SFR is used by the MBS, it is shown that the CP is maximized when the PU uses the same frequency resources as used by the center region.