Research On The Algorithm Of Joint Detection And Decoding For Serially Concatentated System Based On TTCM And CPM

CPM(Continuous-Phase-Modulation),as a kind of constant envelop modulation scheme ,it is better than the traditional memoryless modulation schemes in the sense that it is not sensitive to the nonlinear class C amplifier, which means 2~4dB gain can be obtained compared to those use A class(or B class) amplifier. Because of these, it is widely used in the communication systems such as satellite ,mobile radio and station..This paper mainly deals with the concatenated coded modulation based on CPM. Generally speaking, the performance of specified CPM scheme is closely related to the modulation order, modulation index, memory length and pulse shape. To achieve energy-efficiency and band-efficiency by employing small modulator index will degrade the performance in term of BER. To solve this problem,we propose a concatenated system using CPM and Turbo-TCM as the inner code and outer code independently, demodulation and decoding runs iterarively. The Turbo-TCM has a high code rate as well as good performance, such that the entire system maintains narrow band and high information rate.Considering that in practical scene, noncoherent detection of digital signals is an attractive strategy in situation where carrier phase recovery is difficult. Most of the drawbacks of phase-locked-loop(PLL) circuits used to approximately implement coherent detection, may be avoided by noncoherent detectors .Specifically, typical problems of PLLs such as false-locks, phase-slips, or losses of lock caused by severe fading, Doppler shifts, phase noise, or oscillator frequency instabilities are simply by-passed..By employing Osbsrne-Luntz receiver the noncoherent detector we can break the 3dB gap between coherent and noncoherent detection..Compared to most of the current CPM concatenated systems, the scheme proposed in this paper operates on 8-ary, symbol-level, narrowband and high rates. We investigated the impact of modulation order, modulation index. and pulse shape to the system and obtain some useful conclusions...