A reduced iterative decoder for power and bandwidth efficient serially concatenated continuous phase modulation

A reduced iterative decoder for power and bandwidth efficient serially concatenated continuous phase modulation (SCCPM) based on state fusing is proposed in this paper. The proposed algorithm is based on reduced state sequence detection (RSSD) used for CPM and applied to the inner CPM with finite state machine (FSM) structure. System design criterion and performance analysis are listed. Simulation results for binary 3RC signal with h = 1/2 and quaternary 3RC signal with h = 1/2 show that quaternary system provides better performance at the equivalent normalized double-sided bandwidth. The reduced iterative decoder of inner CPM with 4 states for binary 3RC CPM with h = 1/2 is degraded by at most 0.2 dB with respect to its optimal 8 state decoder; the reduced iterative decoder of inner CPM with 16 states for quaternary 3RC CPM with h = 1/2 is degraded by at most 0.5 dB with respect to its optimal 32 state decoder.