Pilot contamination mitigation in massive MIMO-based 5G wireless communication networks

Massive MIMO (Multiple-Input Multiple-Output) is one of the most promising technologies to be used in the fifth generation wireless communication networks (5G), which are expected to be deployed as the next generation after the 4G, to provide better throughput and better spectrum efficiency using multiple transmit and receive antennas. Pilot contamination is one of the challenges in using massive MIMO technology in 5G, where pilot is a single frequency control signal transmitted over the communication system for channel state information (CSI). Contamination happens when users in adjacent cells have the same pilot sets. Therefore, channel estimation will interfere at base stations. In this paper, we propose an approach to mitigate pilot contamination in massive MIMO systems deployed in time division duplexing (TDD) 5G cellular networks. The proposed approach is based on coupling two pilot decontamination schemes. Firstly, pilot locations shifting in time to reduce inter-cell interference. Secondly, pilot allocation scheme for channel estimation based on Genetic Algorithms (GA), to optimize the uplink system sum-rate in a low-time complexity. Simulation results are extremely promising and show significant improvements over existing pilot allocation and time-shifted scheme.