Closed loop transmission with precoding selection in LTE/LTE-Advanced system

Closed-loop transmission combined with MIMO (multiple-input multiple-output) and OFDM (orthogonal frequency division multiplexing) technologies have drawn most attentions during development of the 4G systems (fourth generation of mobile communication systems). In LTE (Long Term Evolution) and LTE-Advanced systems, which are proposed by 3GPP (Third Generation Partnership Project) to be the most competitive candidate for the 4G systems, the codebook based precoding scheme is deployed for realizing the closed-loop transmission concept. This scheme introduces the precoding matrix selection at the receiver and precoding operation at the transmitter and achieves a good tradeoff between the system complexity and the performance gain given by the closed-loop transmission. In this manuscript, the authors give a brief overview of the LTE/LTE-Advanced system downlink transmission. Furthermore, different precoding matrix selection criteria are discussed at the aim of optimal receiver design. Following the analytical and numerical results, the authors conclude that the minimum post mean squared error based criterion is the optimal candidate for precoding matrix selection at the receiver in LTE compliant systems.