Large-scale MU-MIMO uplink channel estimation using sounding reference signal

Abstract

This paper proposes a practical channel estimation method for the uplink channel of Orthogonal Frequency Division Multiplexing (OFDM) Large-Scale Multi-User (MU) Multiple-Input-Multiple-Output (MIMO) systems by using user specific Sounding Reference Signal. The method is convenient for hardware implementation since it only utilizes Fast Fourier Transform (FFT), Inverse-FFT and multiplication. Given the OFDM parameters of the Long Term Evolution (LTE), this method is able to support the uplink channel estimation of up to 8 users simultaneously under the multipath channel. Additionally, we applied the raised-cosine windows for separating channel impulse responses of each user individually. The raised-cosine window reduces the Bit Error Rate (BER) for a long delay channel such as the ITU Pedestrian B compared with the rectangular windows. Experiments with 16 antennas at Base Station side, 4 users and 256QAM are conducted to validate the proposed channel estimation.