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

Abstract

The deployment 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 intersystem information 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.

Physical-Layer Transmission Cooperative Strategies for Heterogeneous Networks

“…25) As seen in the Alamouti code, the macro-cell precoder for this case also does not depend on the macro-channel as verified from Eq. (25); this means there is no need to exchange any channel information from the macro-cell to the small-cell system to design the IAfilter matrix.…”

“…Then, we present in detail the proposed methods in Ref. [25], for the case where IA and SFBC are jointly used.…”

“…On the other hand, the SUEs should not interfere with each other. We consider that the SBSs are connected via the backhaul network (optical fibre) to a CU in order to perform joint processing of transmitted signals [25]. The CU has enough DoF (i.e.…”

“…[24]. Moreover, to demonstrate the further reduction of information exchange between the two systems, we proposed a joint IA and space-frequency block code (SFBC) approach [25]. In this chapter, we present the schemes mentioned in Refs.…”

“…In this chapter, we present the schemes mentioned in Refs. [23,25] for a general number of antennas at each terminals and for the case where OFDM modulation is considered. Furthermore, for our SFBC-based schemes, we consider a general formulation of the diversity-oriented joint IA and SFBC method that can be applied for any SFBC.…”