matlab help

hi
i'm new to matlab nd need a help to do my project in matlab.

the project is on gsm network performance in fading channels.
I've succeded in realizing all the blocks till the transmitter antenna. After the modulation(GMSK), the signal to be transmitted is stored in I and Q(the inphase and quadrature phase). For the next step ie to add a noise-rician or/and rayleigh,i could'n find any built in function. Please help me to write a function to add the rician and rayleigh noise to the transmitted signal-I & Q............