Factor Graph Framework for Serially Concatenated Coded CPM With Limiter Phase Discriminator Receiver

The paper addresses the system with the Serially Concatenated Coded CPM (SCCCPM) and the nonlinear limiter phase discriminator receiver. The authors develop the FG framework allowing the use of the SPA factor node marginalization rules involving canonical distributions with finite number of parameters. They show that the straightforward application of the traditional constellation space approach is intractable. They also show that the sampled signal space does not allow an application of the parametrized canonical distributions for the variable nodes densities. The solutions they suggest in the paper stands on using the sampled parametric (phase) space of the CPM for all SPA processing.