No abstract

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.INDEX TERMS Adaptive-rate, diversity-multiplexing tradeoff (DMT), free-space optical (FSO) communication, gamma-gamma channel, log-normal channel, multiple-input multiple-output (MIMO), negative exponential channel, single-rate.

No abstract

In this work, a vehicle-to-vehicle (V2V) visible light communications (VLC) model for two practical scenarios, is proposed. In scenario 1, the random lateral shift of vehicles and the deterministic longitudinal separation between two communicating vehicles are considered, whereas in scenario 2, longitudinal separation between two vehicles is considered to be random, and lateral shift of vehicles is considered to be deterministic. To this end, we emphasize comprehensive modeling of the practical characteristics of the considered V2V-VLC system, such as random path loss due to the random mobility of the vehicle, random lateral shift and random longitudinal separation of the vehicle. Moreover, we analyze the performance of the proposed V2V-VLC model in terms of different metrics under the consideration of a novel channel model. Considering our findings, it is observed that the random lateral shift of the vehicle and the random longitudinal separation between two vehicles have a significant impact on the V2V-VLC system performance. Further, at a distance of 40 m, for example, the path loss penalties for moderate and dense fog weather scenarios are 2 and 3 dB, respectively, compared with the clear weather. Furthermore, the combined impact of path loss and atmospheric turbulence affects the V2V-VLC performance significantly.

No abstract