Block transmission with frequency-domain equalization (FDE) has been proven as an attractive alternative to orthogonal frequency division multiplex (OFDM) for radio frequency (RF) communication, especially at 60 GHz. In this paper, we show that FDE can be advantageously applied for optical transmission over dispersive channels as well, and in particular, in direct-detection systems. We review the optimal coefficients for zero forcing (ZF) and minimum mean square error (MMSE) equalization - both in the case of symbol-spaced and fractionally-spaced sampling, and present promising results for an illustrative visible-light communications (VLC) link based on non-return-to-zero (NRZ) on-off keying (OOK)

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A precise characterization of the Land Mobile Satellite (LMS) channel, that is, the channel between a satellite and a mobile terminal, is of crucial importance while designing a satellite-based communication system. State-of-the-art statistical LMS channel models offer the advantage of requiring only a few input parameters, which include the environment type and the elevation angle of the satellite. However, the azimuth angle relative to the driving direction of the mobile terminal is usually ignored, as its proper modeling requires either an extensive measurement campaign or a significant effort from the user, as a precise geometrical description of the scenario is required. In this contribution we show that the impact of the driving direction on the channel statistics is not negligible and requires to be modeled explicitly. Moreover, we propose a statistical LMS channel model whose parameters are obtained via an image-based state estimation method. The image-based method is verified by a comparison with measured radio frequency signal levels. The proposed method allows obtaining a complete statistical description of the channel for arbitrary elevation and azimuth angles.