chapter4\ex1.m ........\ex10.m ........\ex11.mdl ........\ex11main.m ........\ex2.m ........\ex3.m ........\ex4.m ........\ex5.m ........\ex6.m ........\ex7.mdl ........\ex7main.m ........\ex9.m ........\exchannel.m ........\rayleigh.m chapter4