Modified QR-D and MMSE PMI selection technique for MIMO closed loop spatial multiplexing in LTE/LTE-advanced

Limited feedback closed-loop spatial multiplexing evolved as an attractive technique during the development of Multi Input Multi Output (MIMO) in Long Term Evolution (LTE). Spatial multiplexing involves transmitting independent streams of data across multiple antennas to maximize throughput. Closed-loop spatial multiplexing adapt the system to the current channel state throughout a limited feedback channel. In This scheme precoding matrix selection is performed by the user equipment (UE) while applying the selected matrix by the transmitter. In this paper, we propose a new algorithm for precoding matrix selection, based on QR decomposition and minimum mean square error (MMSE), which has an attractive performance and computational complexity gain, so it can be used to efficiently select precoding matrix at UE side. A review over the existent selection techniques is introduced. Also we provide a comparison between the performance of the proposed techniques and the ones in the review in terms of bit error rate (BER) and computational complexity.