中文说明：
用Baum-Welch算法来迭代估计一个隐马尔科夫模型（HMM）的初始状态概率分布以及其状态转移概率矩阵。其中文件有mainfile_B_W.m为主函数，Baum_Welch.m为Baum-Welch算法迭代函数，Forward_variable.m与Backward_variable.m与Gamma_variable.m与Ksi_variable.m是需要计算的四种因子，B_pdf.m为混淆散射概率密度函数。
English Description：
Baum Welch algorithm is used to iteratively estimate the initial state probability distribution and the state transition probability matrix of a hidden Markov model (HMM). Mainfile_ B_ W. M is the main function, Baum_ Welch. M is the iterative function of Baum Welch algorithm_ Variable. M and backward_ Variable. M and gamma_ Variable. M and Ksi_ Variable. M is the four factors that need to be calculated, B_ Pdf. M is the probability density function of confusion scattering.