A Novel Pilot Assignment Approach for Pilot Decontaminating in Massive MIMO Systems

Abstract

This paper proposes a novel joint pilot assignment (JPA) approach aiming to eliminate pilot contamination in massive multiple-input multiple- output (MIMO) systems. The JPA approach jointly assigns pilots in both the time domain and spatial domain. With JPA, the multi-cell cellular massive MIMO network is divided into four cell groups. Pilot phases of different groups are designed to be successive in time domain, which means that users in different groups send pilots alternately in time domain. During the pilot phase of each group, a greedy spatial domain pilot assignment (SDPA) is introduced with the criterion of maximizing the minimal user signal-to-interference ratio (SIR). This paper shows that the JPA approach significantly eliminates pilot contamination from inter-groups when a finite but large number of base-station (BS) antennas is used, or even completely removed as the number of BS antennas becomes unbounded. Since the minimal uplink user SIR is increased, i.e., the intra-group pilot contamination is also alleviated. Numerical results verify the theoretical analysis.