Research On Estimation Method Of Small-scale Fading Parameters Of Wireless Channel Under Complex Transmission Environment

In recent years,with the rapid development of wireless communication technology,efficient small-scale parameters estimation methods for wireless channels in complex environments have become a research hotspots.In typical radio propagation environments,Rice channel model is commonly used to simulate and study the practical wireless communication scenarios.Rice factor is a good index to measure the quality and fading severity of Rice channel,it is widely used in channel characteristics,link budget calculation,adaptive modulation,channel modeling,MIMO channel capacity estimation and so on.Therefore,the research of Rice factor estimation methods is of great significance.This paper introduces the small-scale parameters of wireless channel,including Doppler frequency shift,delay spread,Rice factor,and their extraction methods.For the Rice factor extraction algorithm,the envelope-based moment estimation methods,mainly the first-and second-order moments method and second-and fourth-order moment estimation methods,are introduced.Through the analysis we can see that the computation of first-and second-order moments estimation is complex,and the expression in closed-form of Rice factor can not be deduced,resulting in high time-consuming and low utility.The second-and fourth-order moments estimation is running fast,but with a accuracy can not meet for high demanding scenarios.In view of the above problems,this paper improves the traditional first-and second-order moments methods,and three improved estimation methods are proposed.For method 1,an improvement of moment estimation algorithm for Rice factor based on Bessel functions is proposed.The algorithm calculates the ratio of moments by typical formula,then the ratio of moments is calculated according to the Bessel approximations with different orders,solves the corresponding Rice factor and its estimation accuracy,then the order of Bessel functions are determined.The simulation results of MATLAB show that method 1 reduces the time-consuming,and obtains a good accuracy especially for small K.The second method is to simplify the formula by using the relationships between the two modified Bessel functions,and correct the simplified formula by least square method,getting a closed expression of moments.The simulation results of MATLAB platform show that the method greatly reduces the time consumption.In method 3,The formula of first-and second-order moments is approximated by rational functions,then the expression of Rice factor is fitted,furthermore,a new closed expression of K based on first-and second-order moments is obtained.Though the simulation results of MATLAB,method 3 is feasible and effective for three channel scenarios: flat Rice fading channel,flat Rice fading channel with noise and frequency selective Rice fading channel.