Anti-Fading Method Of Dual-Slot Extension Based On Weighted-Type Fractional Fourier Transform Domain

As communication systems become more complex,Channel fading characteristics are not only single time-domain selective channel or frequency-domain selective channel caused by Doppler frequency shift or multipath effect.Doppler frequency shift and multipath effects coexist in more and more dual-dispersion channel scenarios.Channel fading is one of the main reasons affecting system performance.In order to resist the influence of channel fading on system performance,diversity technology is a commonly used method.However,when using diversity techno logy to resist channel fading,it usually takes up more system resources,so that the system capacity is reduced and the multiplexing gain of the system is affected.In order to solve the problem that the diversity gain and the multiplexing gain cannot be obtained at the same time,this paper proposes a method of double-slot expansion.The dual-slot extension method realizes time slot expansion by zero-padding the original signal in other time slots,and then uses Weighted-Type Fractional Fourier Transform(WFRFT)to average the energy,and WFRFT distributes the energy of one time slot to the zero-padded signal to WFRFT.In dual-time slots.A certain diversity gain is obtained by mutual compensation of energy in the dual-time slots.The zero padding section can insert other signals that are not zero in the time slot,without affecting system capacity.This paper mainly studies whether this method can obtain a certain diversity gain under the condition of full multiplexing gain,and realize the combination of diversity and multiplexing.This paper first introduces the dual-slot extension method,the energy distribution of the processed signal in two time slots,and analyzes the principle of its anti-fading performance.On the basis of this,in order to improve the system performance under the dual-distributed channel,the dual-slot expansion method is combined with the traditional four-term weighted fractional Fourier transform(4-WFRFT),because WFRFT is greatly affected by the weighting coefficient.The change of the weighting coefficient will affect the error rate of the system.Therefore,this paper makes a certain analysis for the optimal selection according to the change of the time-frequency energy distribution of the weighting coefficient.The simulation results show that the system performance can be improved by combining the two-slot expansion method with 4-WFRFT,and the optimal weighting coefficient is used to optimize the system performance.Then,in order to further expand the application of the dual-slot extension method in the communication system and improve the system performance under the single-diffusion channel,the two-slot expansion method is combined with two-component signal.Combine.According to the dual-slot expansion method,the change of the symbol energy distribution caused by the original two time-domain weighted signals and the variation of the sub-carrier bandwidth and quantity caused by the original two frequency-domain signals are analyzed under the time-selected channel and the frequency-selected channel.System performance.Change the degree of channel fading to analyze its impact on system performance.From the simulation results,under the time-selective channel,the dual-slot expansion method can improve the performance of two time-domain systems and two frequency-domain systems.Under the frequency-selected channel,there is no impact on the performance of the two time-domain systems,but it will reduce the error performance of the two-frequency domain system.