Coverage and Load Balancing in Heterogeneous Cellular Networks with Minimum Cell Separation

In this paper, we consider a downlink heterogeneous cellular network (HCN) where K tiers operate in a common spectrum and differ in terms of transmit power, target data rate, and base station (BS) density. We employ a repulsive cell activation (or planning) in the HCN by ensuring a minimum separation distance between interfering BSs in each tier. We consider a modified Matern hardcore process (MHP) for rendering a minimum separation distance between the BSs, which is realized by outweighing random BS distribution for closed and open access networks. Repulsive cell activation not only improves the coverage probability but also plays a role in balancing per-cell loads effectively according to varying user density. Assuming a finite BS capacity in terms of a limited number of per-cell users, we point out the importance of a relative BS density control between the tiers, and propose a tier-wise density and power control by introducing a load factor for configuring a HCN distributively while satisfying per-tier user throughput constraints given user density.