Pilot Decontamination using Time-shifted Pilot and Data-aided Channel Estimation for Massive MIMO

In this paper, we focus on pilot contamination problem in multi-cell massive multi-input multi-output (MIMO) systems. In general, orthogonal pilot across users and cells leads to bandwidth inefficiency. We propose an uplink transmission protocol design in which the pilot portions of users overlap with data from other cells and even partially overlap across cells. Semi-blind algorithms are applied to separate the data streams from user equipments (UEs). With the proposed protocol and semi-blind algorithms, the pilot contamination is greatly reduced. The simulation results show that with the help of semi-blind algorithm employing Constant Modulus Algorithm, the system performance is superior compared to that of the existing schemes.