Research On Single-channel Reception Techniques Of Paired Carrier Multiple Access Signals

Paired carrier multiple access?PCMA?signal is the co-frequency mixture of uplink signals sent by different ground station,which is mixed by the satellite repeater after uplik signals transponded in the satellite communication process.Due to the conservation of frequency band resource and anticapture interception and other properties,it has being widely used in various important communication occasions,and because the single-channel receiving system is simpler and lower in cost,the PCMA signal single-channel receiving technology has a broad application prospect.With the rapid growth of communication services in the recent years,more and more satellites communication digital modulate types are used to further improve the channel utilization,thus PCMA signals have became more and more complex.Targeting at the single-channel receving of PCMA signal,this article mainly carries on the depth research on PCMA signal recognition,parameter estimation under high-order?8PSK?modulation,and separation algorithm combined with SISO decoding depth.The main work and innovation points of this paper are as follows:1.Aiming at the problem of detecting PCMA signals from common satellite digital modulation signals and identify the specific modulation mode,three kinds of practical PCMA signal detection algorithms are compared with different parameters,and the detection algorithm of single-channel mixed signal based on signal-noise ratio estimation has excellent performance on PCMA signal and doesn't require timing synchronization of the received signals.It also simulates The modulation mode recognition algorithm of PCMA signal based on square spectrum,quartic spectrum and high-order cumulant of the PCMA signal,analysis the threshold setting range,and designs the PCMA signal detection and identification process,the detection and identification performance of common mixed modulation PCMA signals is well.2.A hierarchical searching joint parameters estimation algorithm based on statistics of log-likehood ratio?LLR?is proposed for non-data aided parameters estimation of higher order modulation?8PSK/16QAM?PCMAsignals.ThestatisticaverageonLLRfrom Gibbs-sampler-based separator is used to represent the accuracy of parameters estimation;the parameters are more accurate when LLR is greater.The parameters are searched in their section,and the parameters which makes the LLR greatest were estimation results.The hierarchical searching method is used to reduce the search complexity;the performance is improved by the iteration.Compared with the traditional parameter estimation algorithm,proposed algorithm does not need any priori information and can be applied to the parameters estimation of 8PSK and 16QAM modulated single-channel mixed signal.3.A depth joint algorithm on joint separation-decoding is proposed to solving the problem that the traditional algorithm can't be convergent beacause the bit error ratio of saperator is beyong the error correcting capacity of decoder for PCMA signals with LDPC-coded.The log likehood ratio?LLR?of variable nodes are alternatively updated by the single symbol by symbol steps of decoding or separation,the LLR magnitude are small and it is easy and timely to rectify by separation steps.Decoding will work after the bit error rate below the threshold,the algorithm convergences finally.Simulation results shows that the convergence threshold was declined and performance was enhanced by uniting single step of separation and decoding,and good tolerances of the proposed algorithm towards noise for 8PSK mixing signals when bit error rate is 10^-3.