Serially concatenated continuous phase modulation with LDGM codes: Property, Optimization, and Design Principles

Paper in proceeding, 2005

We propose a new scheme of serially concatenated continuous phase modulation (SCCPM) by using nonsystematic low density generator matrix (LDGM) codes as the outer code. A property of the LDGM code degree is investigated. We use the EXIT chart/function to optimize the LDGM codes. The EXIT function of CPM with a fixed SNR (Signal-to-Noise-Ratio) is shown. We derive the union bound to analyze the error floor performance. Design principles are proposed from the analysis process. Numerical results show that this scheme converges earlier (lower SNR) than previous SCCPM for iterative decoding.