Weight-Counting Based Greedy Pilot Allocation in Cell-Free Massive MIMO

Pilot reuse caused by the limited number of orthogonal pilots brings serious pilot contamination to cell-free multiple-input multiple-output system. This paper focuses on the issue of pilot assignment to mitigate pilot contamination. In the proposed scheme, the existing Basic pilot allocation algorithm which proposes a greedy pilot allocation algorithm based on weighted counting is improved. Specifically, we first use large-scale fading coefficient to evaluate channel status of users, so as to determine the pilot allocation sequence for users. Then, a threshold for the number of pilot frequencies is introduced to avoid reusing one pilot too much. Simulation results show that the proposed algorithm outperforms the original algorithm and achieves a significant improvement than most of classical algorithms.