LAUSR

This letter considers downlink wideband channel estimation in an asymmetrical full-digital system where the number of uplink receive radio frequency chains is less than that of the downlink. This channel inconsistency will reduce downlink channel estimation accuracy. To deal with this problem, we adopt the coprime array topology in uplink receive antennas. Then, two iterative algorithms which are based on alternating direction method of multipliers and block-sparsity orthogonal matching pursuit, respectively, are developed to rebuild downlink channel. Simulation results demonstrate the effectiveness of the proposed scheme in the asymmetrical full-digital system.