Analysis and Optimization of Inter-tier Interference Coordination in Downlink Multi-Antenna HetNets with Offloading

TL;DR

This paper proposes an interference nulling scheme in multi-antenna HetNets to improve offloaded user performance by managing inter-tier interference, deriving optimal parameters and comparing with existing schemes.

Contribution

It introduces a stochastic geometry-based analysis of interference nulling in HetNets and identifies optimal degrees of freedom for interference management.

Findings

IN scheme outperforms simple offloading and ABS schemes

Performance gains are significant in large antenna regimes

Analytical expressions enable optimal interference management design

Abstract

Heterogeneous networks (HetNets) with offloading is considered as an effective way to meet the high data rate demand of future wireless service. However, the offloaded users suffer from strong inter-tier interference, which reduces the benefits of offloading and is one of the main limiting factors of the system performance. In this paper, we investigate an interference nulling (IN) scheme in improving the system performance by carefully managing the inter-tier interference to the offloaded users in downlink two-tier HetNets with multi-antenna base stations. Utilizing tools from stochastic geometry, we first derive a tractable expression for the rate coverage probability of the IN scheme. Then, by studying its order, we obtain the optimal design parameter, i.e., the degrees of freedom that can be used for IN, to maximize the rate coverage probability. Finally, we analyze the rate coverage probabilities of the simple offloading scheme without interference management and the multi-antenna version of the almost blank subframes (ABS) scheme in 3GPP LTE, and compare the performance of the IN scheme with these two schemes. Both analytical and numerical results show that the IN scheme can achieve good performance gains over both of these two schemes, especially in the large antenna regime.