Abstract: An iterative receiver scheme cascading Turbo codes with Continuous Phase Modulation (CPM) is proposed for low Signal to Noise Ratio (SNR) and narrowband applications. According to Rimoldi decomposition model of CPM, the purpose of sharing-information and correcting-complementary is achieved by combining the inner iterations with outer iterations. Turbo iterative detection is introduced and Soft-Input Soft-Output (SISO) demodulation and decoding algorithms are adopted. For reducing the iteration delay, a novel dynamic iteration stopping algorithm is presented based on A Priori Probability Decision (APPD). The likelihood at different iteration time is derived and analyzed. Turbo-CPM system model is built and simulation is carried out. Simulation results show that the error correction performance of the proposed iterative scheme is much better than that of the pipelining cascade at very low SNR. Meanwhile, the proposed stopping algorithm can not only reduce the iteration delay, but also improve the system convergence and reliability.

Key words: communications technology, Turbo codes, continuous phase modulation, iterative detection, a priori probability decision