Hierarchical modulation

It has been widely proven and included in various standards, such as DVB-T, MediaFLO, UMB (Ultra Mobile Broadband, a new 3.5th generation mobile network standard developed by 3GPP2), and is under study for DVB-H. Hierarchical modulation is also taken as one of the practical implementations of superposition precoding, which can help achieve the maximum sum rate of broadcast channels.

When hierarchical-modulated signals are transmitted, users with good reception and advanced receivers can demodulate multiple layers.

For a user with a conventional receiver or poor reception, it may only demodulate the data stream embedded in the base layer.

However, traditional hierarchical modulation suffers from serious inter-layer interference (ILI) with impact on the achievable symbol rate.

In better signal conditions, the detector can establish the phase and amplitude more precisely, to recover four more bits of data ('1101').