Considering only different TX delay is not sufficient to model multipath: you shall also introduce an attenuation factor for each ray, because multipath propagation affects not only the phase (modeled by the delay), but also amplitude.
in dealing with multipath channels , you can use the Matlab's rayleighchan and ricianchan functions, pass the signal through the channel using the filter command.
these channels take several parameters, including the attenuation coefficient and the delay for every path .