Group Zero-Forcing for Dense Small Cell Network With Static Pilot Reuse.

In this letter, we consider the uplink in a dense small cell network (DSCN) with static pilot reuse, where the user terminals (UTs) in far-distant small cells using the same pilot are assigned to one group, whereas the UTs in neighboring small cells employing orthogonal pilots are allocated to different groups. With large pilot reuse factor, the DSCN has less intra-group interference resulting from pilot contamination in the same group. However, it is difficult to mitigate the inter-group interference caused by co-channel interference in the different groups, which will severely degrade the system performance. To this end, we propose a group zero-forcing (GZF) receiver which actively nullifies the strongest inter-group interferers among all neighboring user groups. For the proposed scheme, we derive exact expression of the uplink per-user achievable rate with GZF. Simulation results verify our theoretical analysis and demonstrate that proposed GZF scheme is very effective in suppressing inter-group interferences.