Filter Distortions in Ultra High-Throughput Satellites: Models,
Parameters and Multicarrier Optimization
Abstract
Ultra high-throughput satellite systems are expected to play an
essential role in future beyond 5G and 6G networks. These systems must
remain as flexible as possible to adapt to heterogeneous traffic
demands, while also delivering the highest possible rate for dedicated
services. Satellites flexible payloads are increasingly employing
wideband output multiplexers. In this context, it is now more important
than ever to evaluate frequency-dependent degradations on multicarrier
signals. In particular, it is critical to characterize the distortions
entailed by the output multiplexers filters. In this paper, models are
presented and novel formulas are derived to determine the
carrier-to-interference ratio resulting from these distortions.
Derivations are oriented towards the applicability of either
high-accuracy (e.g., for link budget) or low-complexity calculations
(e.g., for real-time carrier allocation). The influence of key
parameters such as the optimal decision instant, symbol rate and
roll-off factor is thoroughly analyzed. Furthermore, formulas are
evaluated in a practical scenario: the dynamic carrier allocation
optimization. They are combined with efficient optimization algorithms
to obtain the best performance based on user fairness. Relevant metrics
such as accuracy, complexity and allocation gain are also investigated.
In the end, the application of the proposed formulas and algorithms
leads to a significant allocation gain that is increasing with the
number of carriers. The feasibility of real-time dynamic carrier
allocation to further increase the capacity of the next generation of
satellite systems is emphasized.