Abstract

Closed-loop transmission combined with MIMO (multiple-input multiple-output) technologies have drawn most attentions during development of the LTE (Long Term Evolution) and LTE-Advanced systems. In LTE/LTE-A, the codebook based precoding scheme (termed as PMI-Precoding Matrix Index selection) is deployed for realizing the closed-loop transmission concept. In addition, dynamic transmission mode selection between the spatial multiplexing and transmit diversity, termed as RI (rank indicator) selection, and the adaptive MCS (modulation and coding schemes) selection, realized as CQI (channel quality indicator) selection are also deployed in LTE systems to provide more robust link connection. In this manuscript, the authors focused on the study of selection criteria on the feedback parameters in closed-loop transmission in LTE systems. With joint selection of the PMI, RI and CQI, the authors illustrate an impressive performance improvement given by closed-loop transmission in contrast to open loop transmission and furthermore conclude that the maximum mutual information is one of the optimal criteria for parameters selections.

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