Research On Noise Suppression Of VWDK Modulated Signal Based On Wavelet Transform

With the surge in demand for communications capacity, and scarcity of the electromagnetic spectrum resources is becoming a big problem, a new wireless communications technologies with high frequency bandwidth efficiency is becoming a hot issue.UNB modulation modulation technology is a new type of wireless digital mudulation technolohy; as the energy of UNB modulated signal concentrated in a very narrow band, with high bandwidth efficiency, UNB modulation technology is expected to be the core technology of band-limited digital communication system with high-speed transfer rate.UNB is one kind high frequency bandwidth efficiency technology, but at the expense of reducing performance of noise suppression, therefore, the conventional communication system of UNB is weak at noise suppression, has a bad adaptability to the wireless channel.In order to improve the capability of noise suppression, the paper selected VWDK as the research object,focus on noise suppression methods of VWDK modulated signals.To begin with,focusing on the characteristics of the UNB signal,introduce the basic theory of VWDK, show the mathematical model and study the waveform design of signal, analysis the technical characteristics of VWDK from mathematical theory, further more, analysis the signal power spectrum on the simulation platform, get the possibility of signal optimization.Simulation results show that the optimal signal further improves the spectrum efficiency, but no decrease the compromising system performance.Secondarily, focusing on the characteristics of modulated signal, try to rearch the additive and multiplicative interference for VWDK modulation system and the performance of the VWDK modulation system.Simulation results show that the performance of VWDK modulation system is greatly impacted by the noise interference and multipath interference, which the main factors of system performance degradation.Finally, focus on the problem that noise suppression of communication system is not high, use the difference between the signal and noise in wavelet domain, propose noise suppression method based on wavelet transform, show noise reduction principle and mathematical model,performance, results show that performance of the system is improved a lot by the wavelet on noise suppression.