Abstract:In order to suppress the pilot contamination in Massive MIMO system,a pilot scheduling scheme based on path loss to perform user grouping (PLUG) was proposed.The proposed PLUG scheme divided the users into the center user group and the edge user group according to different levels of pilot contamination.The proposed PLUG scheme assigned the same pilot sequences to the center users who suffering from slight pilot contamination and assigns orthogonal pilot sequences to the edge users who suffering from severe pilot contamination,thus inhibiting the impact of pilot contamination.The PLUG scheme assumed that the number of edge users in each cell is the same.To improve flexibility of PLUG,an improved pilot scheduling scheme based on path loss to perform user grouping (IPLUG) was proposed.By introducing the decision parameters,the strategy dynamically grouped and selected the number of edge users per cell.It avoided users in good channel conditions being wrongly divided into edge user group which would increase the pilot overhead,or users in bad channel conditions being wrongly divided into center user group whichwould decrease the quality of communication.In this way,the accuracy and rationality of user grouping were improved. Theory analysis and simulation results showed that the proposed scheduling can improve the channel estimation normalized MSE,uplink SINR and achievable rate of edge users with little performance loss of center users.In conclusion,the proposed schemes can effectively suppress the pilot pollution of Massive MIMO system and reduce the probability of communication interruption.