Rate-adaptive FSO communication via rate-compatible punctured LDPC codes

In this paper, rate-adaptive free-space optical (FSO) communication is studied using experimental data measured over a 1.87 km terrestrial FSO link in different weather conditions. To accommodate to the channel gain fluctuations induced by atmospheric turbulence and/or weather variations, a rate-adaptive communication system is implemented by puncturing low-density parity-check (LDPC) codes in a rate-compatible fashion. Beside the conventional random puncturing method, an optimized intentional puncturing technique is employed. Using experimental data and on-off-keying (OOK) modulation, the performance of the rate-adaptive FSO system operating at different signaling rates is evaluated. Unlike uncoded OOK, the rate-adaptive technique provides reliable and efficient FSO communication under different weather conditions and scintillation indices. Applying intentional puncturing can further improve the efficiency of the FSO system in terms of throughput.