Pilot Optimization and Channel Estimation for Multiuser Massive MIMO Systems

摘要

This paper proposes novel pilot optimization and channel estimation algorithmfor the downlink multiuser massive multiple input multiple output (MIMO) systemwith $K$ decentralized single antenna mobile stations (MSs), and time divisionduplex (TDD) channel estimation which is performed by utilizing $N$ pilotsymbols. The proposed algorithm is explained as follows. First, we formulatethe channel estimation problem as a weighted sum mean square error (WSMSE)minimization problem containing pilot symbols and introduced variables. Second,for fixed pilot symbols, the introduced variables are optimized using minimummean square error (MMSE) and generalized Rayleigh quotient methods. Finally,for $N=1$ and $N=K$ settings, the pilot symbols of all MSs are optimized usingsemi definite programming (SDP) convex optimization approach, and for the othersettings of $N$ and $K$, the pilot symbols of all MSs are optimized by applyingsimple iterative algorithm. When $N=K$, it is shown that the latter iterativealgorithm gives the optimal pilot symbols achieved by the SDP method.Simulation results confirm that the proposed algorithm achieves less WSMSEcompared to that of the conventional semi-orthogonal pilot symbol and MMSEchannel estimation algorithm which creates pilot contamination.