Soft-PIC Frequency-Domain Equalization in Iterative MIMO Receivers for the LTE-A Uplink

Single-carrier frequency-division multiplexing access (SC-FDMA) has been adopted as transmission scheme in Long Term Evolution (LTE) uplink to ensure low peak-to-average power ratio (PAPR). SC-FDMA inherently creates significant intersymbol interference (ISI), especially in large bandwidth scenarios. Additionally, inter-antenna interference (IAI) caused by transmitting spatially-multiplexed data streams in multiple-input multiple-output (MIMO) antenna systems further corrupts the received signal, making reliable estimation of the transmitted signal a computationally complex task. In this paper we propose an iterative receiver including a frequency-domain equalizer that mitigates both ISI and MAI jointly. The equalizer takes soft-input values in addition to the received SC-FDMA symbols into account to perform parallel interference cancellation (PIC). This soft-input is determined from decoders output values obtained in the previous receiving process, leading to equalization-decoding iterations. Simulation results for the LTE-Advanced uplink show that the proposed approach achieves considerable performance gains compared to non-iterative receivers.