Iterative Decoding Of Serially Concatenated Continuous Phase Modulation System And Its Improvement

To improve the reliability and effectivity of information transmission is always the goal which we pursuit in the field of communication.Error correction coding is an important methord to improve the reliability of information transmission.Shannon pointed out the direction for the channel coding technology in his famous thesis on "A mathematical theory of communication" in 1948.In the existing military communication systems,we should achieve stable and high speed data communications in poor communications environment, such as mobile,multi-path,and dynamic etc.,which requires coding and modulation systems with high efficiency of power and spectrum correspondingly.In this thesis,Serially Concatenated Continuous Phase Modulation(SCCPM) system is studied in detail.The SCCPM system is based on Turbo code and Continuous Phase Modulation technology.Performance of the SCCPM system is analyzed particularly.The main content of this thesis as follows:(1) The coding and iterative decoding principle of Turbo code(PCCC) and Serial Concatenated Convolutional Codes(SCCC) are studyed.Enough simulations on PCCC and SCCC in MATLAB is given.The difference between SCCC and PCCC on performance is studied.The posterior probability algorithms(MAP,SISOetc.) are also derived in detail.(2) The principle of CPM is studied.The CPM signal is described on trellis.Given the inherent memory of CPM,decomposition module is introduced in this thesis.The outstanding performance of the decomposition module is also analyzed.(3) The SCCPM system is based on Turbo code and CPM.Performance of the SCCPM system is analyzed detailedly.Also a more detailed analysis on parameters,such as:iterleaver length,iterative number,modulation index of CPM,correlative length of CPM,baseband impulse of CPM and convolutional code'generator matrix etd,which affect the performance of the SCCPM system is given.(4) The complexity of iterative decoding of the SCCPM system is analyzed in detail. The CPM signal can be expressed as a sum of finite number of time limited amplitude modulation pulses by Laurent Decomposition.The optimum receiver of CPM is simplified by Laurent Decomposition.By using the property of Laurent Decomposition,the numbers of matched filter and trellis state can be redeced apparently.As a result,the complexity of iterative decoding of the SCCPM system can be reduced apparently,too.The above idea is proved by theory and simulations in the thesis.(5) The conceptions of ring CC and ring RSC are introduced,and then the plans of the two encoders are given.Based on these,the concept of ring SCC is proposed.For SCCC system and SCCPM system,different new schemes are suggested and validate.From the results,a conclusion can be drawed:for both SCCC system and SCCPM system,the suggested schemes outperform the originals,with the same or similar computational complexities.