Joint IA and SFBC Macrocells and Small-Cells Coexistence under Minor Information Exchange

Abstract

Thedeployment of small-cells within the boundaries of a macrocell is considered to be an effective solution to cope with the current trend of higher data rates and improved system capacity. In the current heterogeneous configuration with the mass deployment of small-cells, it is preferred that these two cell types will coexist over the same spectrum, because acquiring additional spectrum licenses for small-cells is difficult and expensive. However, the coexistence leads to cross-tier/intersystem interference. In this context, this contribution investigates interference alignment (IA) methods in order to mitigate the interference of macrocell base station towards the small-cell user terminals.More specifically, we design a diversity-oriented interference alignment scheme with space-frequency block codes (SFBCs).The main motivation for joint interference alignment with SFBC is to allow the coexistence of two systems under minor intersysteminformation exchange.The small-cells just need to know what space-frequency block code is used by the macrocell system and no intersystem channels need to be exchanged, contrarily to other schemes recently proposed. Numerical results show that the proposed method achieves a performance close to the case where full cooperation between the tiers is allowed.