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.