A comparison of relay selection and repetition coding for free-space optical communication

A major problem in free-space optical (FSO) communication is the atmospheric turbulence-induced fading. In this paper, we consider two fading-mitigation techniques for FSO links. We study cooperative FSO links with relay selection and repetition coding with intensity modulation and direct detection (IM/DD) over lognormal fading channels. To compare these two scheme´s performance, we derive Bit-Error-Rate (BER) expressions analytically. Furthermore, we confirmed our analytical results through Monte Carlo computer simulations. Our performance analysis results show that however in low SNR values repetition coding performs better than relay selection but in high SNR values relay selection outperforms repetition coding.