A Novel Pilot Assignment Scheme in Massive MIMO Networks

In this letter, we propose a novel pilot assignment scheme for the pilot contamination problem in massive multiple-input multiple-output multi-cell networks. Based on the asymptotic signal-to-interference-plus-noise ratio (SINR), the proposed pilot assignment scheme adopts the harmonic SINR utility function to quantify the fairness of all users in the network. Specifically, we formulate the pilot assignment problem as a minimum-weight multi-index assignment problem. For a two-cell network, this problem can be solved by the Hungarian algorithm with a strongly polynomial complexity. For the general multi-cell networks with more than two cells, this problem is in general NP-hard and we propose an efficient algorithm to obtain a suboptimal solution. The numerical experiments show that the proposed algorithms outperform other conventional pilot assignment schemes.