Performance of coded time-diversity free-space optical links

Depending on the tolerable delay latency, we can benefit from some degree of time diversity in free-space optical links, by employing channel coding and interleaving. We present a comparative study of the performance of different channel coding techniques at the presence of time diversity. We show that turbo-codes are particularly efficient under strong turbulence conditions. For relatively weak turbulence, however, a simple convolutional code makes a good compromise between decoding complexity and performance. We also address the problem of channel estimation at the receiver, and show that only few pilot symbols are sufficient to provide a performance close to the case of perfect channel knowledge.