Study On Modulation Index Estimation Algorithm Of Multi-h CPM Signal

With the rapid development of modern communication technology and the rapid increase of people's demand for transmission,the spectrum resource of wireless communication becomes scarce,which inspire people to study more efficient and more advanced modulation mode.Continuous phase modulation is widely used in wireless communication systems,which has constant envelope,continuous phase,efficient spectrum and bandwidth utilization and other advantages.With the mature of CPM technology,Multi-h CPM technology becomes the core technology of the next generation of military and civilian wireless communication,which has been extensively studied by many scholars.But the cycling modulation index increases the complexity and difficulty of demodulation,which becomes a serious impediment of the widespread application of Multi-h CPM.As we know,in the non-cooperative communication system,the receiver has no knowledge of the sender's modulation mode and parameters,which needs blind parameter estimation to realize signal's accurate demodulation and receiving.For Multi-h CPM,the cyclic changing of the modulation index is a distinctive character which different from other CPM signals,at the same time,this indicator also brought great difficulty to its blind demodulation,so accurate estimations of the modulation index naturally become an important support for Multi-h CPM signal blind demodulation.In this paper,we study the estimation of Multi-h CPM signal modulation index in non-cooperative communication system,the results are given as follows:Firstly,the modulation index estimation methods of CPM signals we are studied,The three classical methods(which based on periodicity,cyclical stationarity,higher-order cumulant)are compared by simulations.Through the analysis of the composition of the expression of multiple modulation index continuous phase modulation,we propose that classify modulation index of the same symbol as a group and make up a single modulation index CPM signal.Then,using the above three methods to estimate each modulation index and achieve modulation index estimation of full response Multi-h CPM signal.As to part response Multi-h CPM signal,the estimation method based on the cyclic stationary characteristic is directly applied to the signal,and the average value of the Multi-h CPM modulation index is estimated.Secondly,a modulation index estimation method based on K-S detection is proposed.We find that the slope of the average phase accumulation distribution function is different as the modulation index changes,Based on this theory,we can estimate the modulation index under given modulation index set.The algorithm is tested by simulation and the algorithm's performance is analyzed.Finally,we summarizes the contents of this paper,then point out some defects of the given method,and the future research area.