HOW TO EXPLOIT MOBILITY TO MITIGATE PILOT CONTAMINATION?

To tackle the uplink pilot contamination problem in massive multiple-input multiple-output (MIMO) systems, current researches only relied on the angle of arrival at the base station. However, this information is insufficient when the users share the same scattering environment. In this paper, we propose a novel strategy by exploiting the user mobility. Due to limited scatterers around the users, we first investigate the channel sparsity and derive the corresponding angle-Doppler frequency domain channel power spectrum (AD-CPS). We then propose a method to mitigate the pilot contamination through aligning the AD-CPSs. Compared with the existing works, we further demonstrate the effectiveness of the proposed scheme in supporting more orthogonal pilots when the interfering users exhibit different moving patterns. Simulations verify the superior performance and show that the proposed scheme can serve as an additional decontamination mechanism for the UL pilots in massive MIMO systems.