A Backward-Compatible Solution for Next Generation DVB-C System
In this paper, we propose hierarchical modulation as a backward compatible solution for next generation digital video broadcasting over cables (DVB-C2). Without modifying the architecture of legacy receivers, supplementary data can be transmitted via an added layer superimposed onto the legacy layer, and the resultant increase of transmission power is only a small fraction of that used by the legacy system. To obtain the upper bounds for the achievable throughputs, the modulation constrained capacities are derived for this layered transmission scheme. We formulate the hierarchical constellation design as a nonlinear optimization problem and then solve it through a simplified numerical method, which searches for the appropriate power allocation ratio in one-dimension space. Finally, to examine the inter-operability of channel encoder/decoder between DVB-S2 and DVB-C2, we investigate the error performance of the proposed scheme employing the LDPC codes given by DVB-S2 standard.