A Turbo CDMA System with CPM Spreading Modulation

This paper firstly proposes a decomposed model of CPM modulator which consists of a linear CPE and a memoryless modulator.Based on the error event analysis and recursive feature of CPM signal,a Turbo CDMA system with CPM spreading modulation is proposed,in which CPM modulator as a recursive inner coder can be used to concatenate with other outer coders and interleaver into a Turbo iterative system to improve the performance of CDMA system.With the use of iterative demodulation,despreading and decoding an iterative soft-input-soft-output (SISO) receiver is proposed in this paper,in which MAP and SOVA algorithms are implemented in the demodulator,respectively,and MAP algorithm is realized in the decoder.Simulations have shown CPM spreading modulator as an inner coding modulator can provide the interleaver gain explicitly.