关键词: 大规模多输入多输出, 导频污染, 导频分配, 图着色, 可达和速率

Abstract: Aiming at the pilot contamination problem for massive multiple-input multiple-out (MIMO) systems, a dynamic pilot allocation scheme based on graph coloring was proposed. To allocate pilot more reasonably and mitigate pilot contamination, firstly, an edge-weighted interference graph based on cooperation among cells was constructed to describe the strength of pilot contamination among multi-cell users, whereby two users were connected in different cells by a weighted edge. Then, based on traditional graph coloring theory, the pilot resources were allocated preferentially to the users who were heavily polluted by the characteristics of different weighted edge. The theoretical analysis and simulation results show that, compared with existing distributed pilot allocation scheme, the proposed scheme can reduce the inter-cell interference due to pilot reuse with a centralized mechanism named graph coloring and enhance the uplink achievable sum rates.

Key words: Massive multiple-input multiple-out(MIMO), pilot contamination, pilot allocation, graph coloring, achievable sum rates