A reduced state SISO iterative decoding algorithm for serially concatenated continuous phase modulation (Q2461470)

The paper represents a contribution to the theory of efficient techniques of modulation. It is shown the importance of disposing of high rate data communication in severe mobile communication and in multi-path environments. To such requirements, the continuous phase modulation (CPM) represents a valuable technique. The development of the coding theory led to the elaboration of serially concatenated codes which in combination with Trellis coded modulation gave rise to systems with high spectral efficiency. The use of iterative modulation greatly improved the performances and insured a low complexity in codes. The first section introduces the reader to the bases of CPM. Next, the block scheme of the serially concatenated continuous phase modulation (SCCPM) is presented and analyzed. The iterative decoder of SCCPM consists of two a posteriori decoders. Soft input soft output (SISO) is used. The third section describes the way to reduce the states of the SISO algorithm. Next, an analysis of how to design the proposed system is presented by the use of signal bandwidth and Euclidean distance. Finally, the proposed approach is validated via simulations.