Free-space optical (or optical wireless) communications represent an attractive technology for the realization of high-bandwidth wireless communications. However, for propagation through the atmosphere the characteristics of the optical signal are different from those of the signals from, e.g., fiber channels or radio-frequency wireless channels, and therefore the error characteristics on these links are also different. For evaluating fading mitigation techniques for optical wireless communications a channel model is needed that can be easily used by protocol designers. Existing channel models for optical wireless communications are based on atmospheric propagation theory and therefore require a deep physical understanding of the optical propagation through the atmosphere. The goal of this publication is to develop a simplified approach for modeling the received power dynamics of the atmospheric free-space optical channel. The proposed model consists of a random number generator and a low-pass filter and is therefore easy to implement and use. This approach is only valid for systems utilizing intensity modulation with direct detection, but this limitation is acceptable since most commercially available systems use this modulation format. The channel model is developed based on the statistics of received power measurements from a maritime-mobile link, a land-mobile link, and a satellite downlink.
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