Study On The Feature Parameter And Identification Of Wavelet Packet Modulation Signal

Modulation identification technology of a signal is a rapidly evoling area. It has been widely applied to military communication and business telecommunication area. The extract of a signal's feature is a part of the modulation identification of signals. The modulation identification technology based on feature parameters methods cuases great concern because this method is simple, safe and adaptable. However, in recent years, the multi-carrier modulation technology has attracted increasing attention since it is an efficient solution to accommodate high data rate and great transmission capacity in broadband wireless communication systems and the automatic identification of multi-carrier modulation cause great concern. Wavelet packet modulation is a new type of multi-carrier modulation technology and it has some unique advantages such as the capability of anti-disturbing, bandwidth utilization, transmission speed and safety. In this thesis, the wavelet packet modulation (WPM) signals and OFDM signals are served as research targets. By extracting the suitable parameter of a signal, this paper is to realize the identification between wavelet packet modulation signal and OFDM signal in the additive Gaussian white channel, Rayleigh fading channel and frequency selective fading channel.1.The basic principles and realization of wavelet packet modulation and OFDM are introduced. Based on fractional Fourier transform, the cluster area of wavelet packet modulation and OFDM signals in the fractional domain is deeded as the classification parameter to realize the recogonition of WPM and OFDM in the additive Gaussian channel, Rayleigh channel and frequency selective channel. The simulation results indicate that this method has high robustness.2.According to the structure characteristics of WPM and OFDM modulation, OFDM needs cyclic prefix because the frequency spectrum of its sub-carrier has high side lobe, however, in WPM there has low side lobe in the sub-carrier frequency spectrum and there is no need to add cyclic prefix. As a result, OFDM signal has a property of auto-correlation. Therefore, using the auto-correlation characteristic of a received signal, the modulation identification between OFDM and WPM in the additive Gaussian channel, Rayleigh channel and frequency selective channel is studied. The effectiveness of this method is done by the computer simulations.