A low complexity iterative soft detection for bit interleaved coded CPM

In this paper, we propose a low-complexity iterative soft detection algorithm for a bit interleaved coded continuous phase modulation (CPM). The reduction of complexity is obtained by using a modulation index at the receiver side which is different from the one used at the transmitter side. This difference is balanced thanks to a soft-input soft-output (SISO) coherent CPM demodulator based on the per survivor processing (PSP) technique. Compared to the state of the art, the error rate performance is improved. We also show that our algorithm converges close to the coherent maximum a posteriori (MAP) algorithm, with a few additional iterations.