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14.3 Compressive Modulation 305
14.3.3 Design RP Codes
An RP code is a linear rateless code which encodes binary digits into multilevel
symbols. It can be represented by a bipartite graph, where left nodes are binary input
and right nodes are encoded multilevel symbols. Every right node has the same fixed
node degree L and the weights of connecting edges are taken from the same set
{w
1
,w
2
,.. . ,w
L
}. The key design parameters for a RP code are the right node degree
L and the set of edge weights.
As the pursuit for RP code arises from the modulation problem, the design objec-
tive naturally is to find a low-complexity code whose output symbols