SUMMARYThe exploitation of adaptive coding and modulation techniques for broadband multi-beam satellite communication networks operating at Ka-band and above has been shown to theoretically provide large system capacity gains. In this paper, the problem of how to accurately estimate the time-variant channel and how to adapt the physical layer taking into account the effects of estimator errors and (large) satellite propagation delays is analyzed, and practical solutions for both the forward and the reverse link are proposed. A novel pragmatic solution to the reverse link physical layer channel estimation in the presence of time-variant bursty interference has been devised. Physical layer adaptation algorithms jointly with design rules for hysteresis thresholds have been analytically derived. The imperfect physical layer channel estimation impact on the overall system capacity has been finally derived by means of an original semianalytical approach. Through comprehensive system simulations for a realistic system study case, it is showed that the devised adaptation algorithms are able to successfully track critical Ka-band fading time series with a limited impact on the system capacity while satisfying the link outage probability requirement.

This paper presents the detailed design and the key system performance results of a comprehensive laboratory demonstrator for it broadband Ka-band multi-beam satellite system exploiting the new DVB-S2 standard with adaptive coding and modulation (ACM). This complete demonstrator allows ill-depth verification and optimization of the ACM techniques applied to large satellite broadband networks, as well as complementing and confirming the more theoretical or simulation-based findings published so far. It is demonstrated that few ACM configurations (in terms of modulation and coding) are able to efficiently cope with a typical Ka-band multi-beam satellite system with negligible capacity loss. It is also demonstrated that the exploitation of ACM thresholds with hysteresis represents the most reliable way to adapt the physical layer configuration to the spatial and time variability of the channel conditions while avoiding too many physical layer configuration changes. Simple ACM adaptation techniques, readily implementable over large-scale networks, are shown to perform very well, fulfilling the target packet-error rate requirements even in the presence of deep fading conditions. The impact of carrier phase noise and satellite nonlinearity has also been measured

SUMMARYThis paper proposes a methodology for designing and optimizing the performance of adaptive coding and modulation (ACM) schemes for the forward link of unicast satellite broadband networks. The proposed technique of general applicability is based on the overall system capacity maximization conditioned on meeting a certain service area coverage for a given outage probability. The paper first derives in detail the method for computing the Shannon-based capacity of a multi-beam satellite system adopting ACM. Then the link efficiency is optimized under different physical layer constraints allowing a more realistic system performance assessment. Finally, to exemplify the methodology application and to quantify the ACM system performance improvement capabilities a study case corresponding to a Ka-band state-of-the-art bent pipe satellite network is provided. The example illustrates the very substantial capacity gain offered by state-of-the-art adaptive modulation and coding schemes utilization compared to current broadband satellite system design approach.

SUMMARYThis paper deals with the system capacity analysis and assessment of the potential advantages provided by the introduction of Adaptive Coding and Modulation (ACM) in the reverse link of multi-beam broadband satellite systems. ACM is intended to increase the system throughput for a given terminal EIRP power by optimizing the individual links physical layer to the current channel conditions. The physical layer adaptation will be driven by the inbound demodulator signal over noise plus interference ratio (SNIR) estimation. A general methodology for ACM physical layer optimization based on the system capacity maximization is also illustrated. A theoretical analysis of ACM systems capacity is performed for both time division multiple access (TDMA) and code division multiple access (CDMA) schemes. As the exact analytical capacity computation results to be very complex while Monte Carlo approach leads to very time consuming simulations, a simplified semi-analytic approach is devised. Numerical results showing the huge improvement in terms of capacity by the ACM adoption are obtained for both the semi-analytic and the Monte Carlo approaches in a realistic study case corresponding to a Ka-band multibeam satellite system. A good match between the two approaches is also demonstrated.

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