Research On OFDM And The Single Carrier Signal Modulation Recognition

In recent years, the communication technology is developing rapidly and theway of the modulation of communication signals is sundry. Therefore, it is becomevery meaningful to do some research on OFDM and single carrier signal modulationrecognition between class, as well as the single carrier signal modulationrecognition within class.However, most traditional algorithms of these two typesmodulation recognitions are complex and have a big calculation. So it is verynecessary to make improvements and reduce the computational complexity of thealgorithms. This thesis does some analysis on the traditional method to reduce thecomputational complexity by extracting the new characteristic parameters.Firstly, for the modulation recognition of OFDM and the single carrier signalsbetween class. This thesis analyzes the principle of OFDM system and the signalcharacteristics and then does the spectrum simulation experiments of these two classsignals. From the comparison of simulation experiment results, these two classsignals have big differences in spectral peaks, spectrum flatness and the side lobeenergy. According to this, this thesis extracts new parameters to make featureextraction based on the the spectrum characteristics and does the simulationexperiments to obtain theoretical judgment threshold of the separation of these twoclass signals. Also, this thesis make recognition on actual data by using the newparameters to verify the effectiveness of the new algorithm.Secondly, for the single carrier modulation recognition within class. This thesisanalyzes the classic Nandi parameter recognition method, and then use a newalgorithm based on iterative algorithm to make the improvement of the classicalgorithm. Through the simulation experiment of the common single carrier signals,it comes to a conclusion that this new algorithm can not only reduce thecomputational complexity, but also keeps a high recognition rate when the signal tonoise ratio is greater than5dB. For further recognition of the actual data, this thesisuses maximum likelihood recognition method and iterative algorithm recognitionmethod separately to make the recognition of it and get the same recognition result.Finally for the modulation recognition in the complex channel environment.This thesis analyzes these two class signals in the situation of multi-path effects, and the Doppler effect. For OFDM, the thesis does the derivation of a new characteristicparameter dn20,a4order cumulative amount to make the recognition between classin the situation of multi-path effects, and the Doppler effect and then does thesimulation experiments. The result show a high recognition rate by using thismethod. For single carrier signal, the thesis analyzes the effects on signals in thesituation of multi-path effects, and the Doppler effect separately, and through addingthe parameter σdfand improving the threshold method to eliminate the impact ofmulti-path effects, and the Doppler effect. Then the thesis does some simulationexperiment. From the result, it comes to a conclusion that these two method aresuitable in the complex channel situation.From the above, this thesis makes improvements of the traditional algorithmsof the OFDM and single carrier signal modulation recognition between class, as wellas the single carrier signal modulation recognition within class and and reduce t hecomputational complexity of the algorithms, at the same time, it analyses the effectsof multipath effects, and the Doppler effect on the signals and give the method tomake the compensation.