Performance Analvsis For Serially Concatenated Continuous Phase Modulation System

Serially Concatenated Continuous Phase Modulation (SCCPM) is the combinationof serially concatenated channel code (SCCC) and continuous phase modulation(CPM). Because of its using iterative decoding, SCCC keeps high codes gain. WhileCPM that a kind of modulation signal with constant amplitude and continuous phase,has a high efficiency of bandwidth and power. SCCPM inherited the fine features ofboth, has a good BER performance.First, the fundamental principle of CPM is discussed and the CPM signal isdescribed on trellis. As the CPM signal can be decomposed into a CPE (ContinuousPhase Encoder) and a MM (Memoryless Modulator), that CPM is an encodingmodulation. On this basis, the spectrum and performance of the CPM signal areanalyzed detailedly.Secondly, the encoding and decoding structures of SCCC are introduced. CPM asan inner code can be serially concatenated with the CC (Convolution Code) as anoutcoder, which is a system called SCCPM both has the channel code and themodulation. Then the MAP algorithm and SISO(Soft-input Soft-output) are discussed.And the simulation of SCCPM system using iterative detecting algorithm isimplemented. Through the system of simulation, we use different convolution codes,CPM modulation indexes, cardinalities, CPM baseband pluses, CPM memoriallengths, the interleaver lengths and the number of iteration. The simulation resultsshow that the system performance gets better with the longer constraint length and thelarger number of convolution code, improves with the increasing number ofcardinality, memorial length and modulation index. Besides, the greater length ofinterleaver and the larger number of iteration can also improve the systemperformance.