Iterative MMSE Transmit and Receive Filter Design for Frequency Selective MU-MISO Systems

We consider a multi-user multiple-input single-output (MU-MISO) scenario, where the decentralized users are served by a centralized transmitter with multiple channel inputs via frequency selective vector channels. For this broadcast setup, we jointly design the transmitter and receivers based on a minimum sum mean square error (MSE) criterion. Contrary to previous work in this field, we do not restrict the receivers to be scalar weights but employ finite impulse response (FIR) receive filters. Since the sum MSE minimization has no closed-form solution neither for linear preceding nor for Tomlinson-Harashima precoding (THP), we propose to use an alternating optimization and prove the convergence of the resulting iterative algorithm. The simulations show that the obtained linear and nonlinear preceding solutions with FIR receivers clearly outperform the state-of-the-art precoders with scalar receivers.