Channel Interleaver Dimensioning for Optical LEO Direct-to-Earth Systems

Following the recent publication of the first recommended standard on optical communications by the Consultative Committee for Space Data Systems (CCSDS), the focus of the standardization group turns now to the optical low Earth orbit (LEO) direct-to-Earth (DTE) satellite link scenario. This scenario is nicknamed optical on-off keying (O3K) due to the choice of this binary modulation format. In optical LEO DTE links the main impairment is atmospheric turbulence, which is a slow fading process with relatively long coherence time (typically some milliseconds). To mitigate this and to allow for any forward error correction (FEC) code to operate properly, a long channel interleaver is usually employed at the physical layer. The present paper provides some practical guidance on how to dimension such an interleaver by performing a realistic numerical analysis based on a comprehensive software simulator, along with a statistical analysis to gain a deeper insight. Overall, this work is meant to support the CCSDS O3K standardization activity.