Performance of modulation-aware iterative equalization in uplink LTE systems

In this paper, advanced multi-user uplink reception algorithms for LTE systems are considered for realistic propagation channels. An iterative modulation-aware MMSE equalizer is implemented to detect parallel data streams from independent transmitters. The proposed algorithm performs iterative cancelation steps based on iterative matrix inversion methods. This process simultaneously reduces the cross-interference power, thus enhancing the overall system performance. Based on the intermediate signal variables, which are approximately marginally Gaussian distributed, the processor uses a conditional estimation function to generate soft symbols from previous iterations to minimize the error variance at the current cancelation step. The performance of this modulation-cognizant proposed equalizer is compared to the baseline linear MMSE processor in terms of bit error rate. It is shown that this new receiver significantly outperforms the baseline algorithm, in particular when simultaneous detection of the data streams is considered and rank deficiency prevents the classical MMSE algorithm from functioning properly.