Diversity-Multiplexing Tradeoff for MIMO-FSO System Under Different Transmission Scenarios With Limited Quantized Feedback

The diversity-multiplexing tradeoff (DMT) in a multiple-input multiple-output (MIMO) free-space optical (FSO) communication with limited channel state information at the transmitter (CSIT) is investigated. Using the limited CSIT based power and rate control strategy, we optimally allocate the power among the good and bad channels in such a fashion that the DMT performance of the system enhances significantly unlike the no-CSIT based MIMO-FSO DMT. In this way, a new limited CSIT based technique/model with optimal power and rate control strategy is proposed to enhance the DMT performance. The optimal DMT is studied for two different transmission scenarios: single-rate and adaptive-rate transmission. It is shown that how the optimal DMT is influenced when the concept of minimum guaranteed multiplexing gain in the forward link is taken into account. It is illustrated that power control based on the feedback plays a vital role in attaining the optimal DMT, and rate adaptation is significant in obtaining a high diversity gain, especially at high rates. Moreover, the analysis of upper and lower bounds on the optimal DMT is done by giving useful insights. Furthermore, a novel study based on the optimal tradeoff between the degrees of freedom and the number of transmit apertures in a coherent MIMO-FSO channel is also done. To validate the results of the proposed model, we compare the derived results with the no-CSIT based MIMO-FSO DMT. It is observed that the proposed technique/model outperforms the no-CSIT based MIMO-FSO DMT.