Effects of non‐uniform quantisation on the interference mitigation using multi‐cell multiple‐input and multiple‐output‐coordinated beamforming

Abstract

In recent years, coordinated beamforming (CBF) has attracted considerable attention because of its effectiveness in intercell interference (ICI) mitigation. To facilitate the operations of CBF for the frequency-division duplex mode, efficient channel state information (CSI) exchanges through backhaul links are necessary. In previous studies, uniform quantisation of CSI has been generally assumed in feedback schemes. Statistically, however, uniform quantisation may not be optimal from the viewpoint of the ICI in CBF, which is mainly caused by the quantisation error (QE). This study proposes a low-complexity cumulative distribution function (CDF)-based non-uniform quantisation method with a limited number of feedback bits for applying more quantisation levels to represent feedback CSI, which occurs with higher probability. This is because a more accurate representation of frequent CSI can lead to a lower QE for reducing the ICI level in most cases. To prove the effectiveness of the proposed CDF-based quantisation scheme, the ICI in the considered two-cell CBF scenario was analysed using several feedback bits. The simulation results proved the higher transmission rate, particularly in cases with fewer feedback bits.