Comparison of Several Demodulation Algorithms about Hierarchical Modulation in Broadcast Communications

Using hierarchical modulation technology is very prevalence in existing digital broadcast system, such as satellite TV. A video source can be split into two streams, one stream is called basic stream, the other is called enhance stream. The basic stream contains high-priority information, it can offer basic visual effect, while the enhance stream contains low-priority information, it can make the visual effect much better. So the hierarchical modulation (superposition coding) consists of a basic constellation and a enhance constellation, but the fact is that basic constellation and enhance constellation will be to influence each other. Analysis will be performed to find an optimum hierarchical modulation´s demodulation algorithm so as to keep the mutual influence to the minimum and let almost receivers can get good reception in larger coverage.