Pilot Allocation Scheme Based on User Grouping in Massive MIMO Systems

Aiming at the pilot contamination problem in massive MIMO systems, based on the analysis results that the frequency of pilot usage can measure the change trend of pilot contamination intensity, a pilot allocation scheme through user grouping is proposed. The users in the target cell are divided into two groups by using the large-scale fading coefficients. In the weak user group with smaller large-scale fading coefficients are allocated according to the pilot contamination intensity. In the strong user group with larger large-scale fading coefficients are allocated according to the frequency of pilot usage. The proposed scheme not only guarantees the fairness of weak users, but also improves the average achievable sum rates of the uplink. Simulation results show that, compared with the smart pilot allocation scheme and the random pilot allocation scheme, the proposed scheme can effectively enhance the performance of the massive MIMO system.