Increased dynamic range multi-rate waveform for mobile satellite communications: Adaptive Coding Spreading and Modulation (ACSM)

For time-division multiplexed satellite communications links, a multi-rate waveform can enable substantial capacity gains over waveforms employing static coding and modulation. Using a multi-rate waveform such as DVB-S2 with adaptive coding and modulation (ACM), a user's data is transported with the most efficient modulation and forward error correction coding point that specific user can reliably receive. Many mobile satellite communication applications require a substantially smaller aperture or a lower-profile antenna as compared to typical fixed-site very small aperture terminals (VSATs) for which DVB-S2 was designed. Over a wide area of operation, these smaller mobile terminals often cannot establish a link that observes regulatory power-spectral density limits using even the most robust modulation and code point that the DVB-S2 waveform offers. By adding the concept of adaptive direct sequence spreading to the adaptive coding and modulation, a more capable multi-rate waveform emerges that addresses a comprehensive set of mobile terminal platform types and scenarios. In this paper, the Adaptive Coding Spreading and Modulation (ACSM) concept is described and the capacity gains are quantified for several case studies. Also, a blockage mitigation technique employed within the ACSM concept that enables communications on train or helicopter mounted platforms is discussed.