Two Laser Selection Scheme for FSO Communication

In order to send the information bits, a conventional transmit laser selection (CTLS) scheme selects the best transmit aperture. Due to the optimal transmit aperture selection, CTLS offers the best possible error performance in a free-space optical (FSO) communication system. Moreover, this optimal error performance is observed under the perfect feedback link scenario. However, a slight error in the feedback information can cause a significant loss in the diversity order. This deteriorates the error performance. To overcome this problem, we propose and analyze a novel grouping-based TLS scheme, called two TLS (TTLS) scheme. In the proposed TTLS scheme, the transmit apertures are divided into two groups and the best aperture in each group is used for transmission of the data. Furthermore, it is observed by the intensive analysis that the proposed TTLS scheme offers a lesser loss in the diversity order as compared to CTLS under the erroneous/imperfect feedback link. Therefore, a significant amount of performance gain can be achieved by the proposed TTLS scheme as compared to the CTLS scheme under a practical (erroneous feedback) scenario.