| With the rapid development of wireless communication,the sudden increase in user data and the shortage of wireless frequency resources have caused many problems.The first is the time-frequency doubly-selective fading channel caused by multipath and highspeed movement,which will bring serious damage to the signal,leading to bit error and delay.Secondly,due to the intrinsic characteristics of the wireless media and the broadcast characteristics of communication signals,the signals are easily intercepted by eavesdroppers and the data are stolen,which seriously threatens the privacy of users.In response to the two types of problems mentioned above,weighted fractional Fourier transform(WFRFT),an emerging signal design and processing method,has been proved to have certain application prospects.This is mainly because the WFRFT transforms the signal into the fractional domain,which changes the energy distribution of the signal on the time-frequency plane,so that the signal is capable to resist timefrequency interference and make the communication in hidden.In essence,the excellent characteristics of this fractional domain signal come from the various signal form provided by the WFRFT.Therefore,starting from enriching the definitions,this thesis first generalizes the WFRFT,and the four new types of generalized weighted fractional Fourier transforms(GWFRFT)with extended boundary value condition are proposed.Then the corresponding principles and basic properties of the transform is studied.The effect of each parameter on the GWFRFT signal is summarized.In the end,this thesis hopes to lay a theoretical foundation for future potential applications by expanding the GWFRFT theoretical system.Based on the proposed GWFRFT,this thesis further designs and proposes a singlecarrier(SC)and multi-carrier(MC)cross-modulation multi-antenna communication scheme,whitch named as cross-modulation system.The system is essentially a hybrid carrier system,but the differenct is that it separates and recombines the SC component and MC component of two input signals.Furthermore,in this thesis,under the timefrequency doubly-selective channel,it is verified that this hybrid carrier system signal can achieve better bit error rate performance than traditional SC and MC signals.Finally,in terms of physical layer security,this thesis analyzes the security performance of the GWFRFT signal in the classic eavesdropping channel model,which mainly includes secrecy capacity,bit error rate,the capability of anti-parameter scanning and so on.Results shows that the GWFRFT has better secure performance than the traditional WFRFT. |
