ACM optimization in DVB-RCS channels for TCP transmissions

In the presence of long-lived TCP connections, Adaptive Coding and Modulation can be effectively used in satellite channels, in conjunction with bandwidth allocation, in order to optimize the trade-off between goodput and fairness, without touching the TCP congestion control algorithm. Nevertheless, the very steep curves that describe Packet Error Rate (PER) versus Ec / N0 (channel bit energy to one-sided noise spectral density ratio) in DVB-S2 hinder the benefit of such an optimization scheme. The situation is different in DVB-RCS, where the concatenation of convolutional and Reed-Solomon codes, though still quite powerful, leaves some margin to jointly exploit ACM and bandwidth allocation procedures. This situation is analysed in this paper, by providing numerical results for a typical Ka band link budget.