In recent years, ns-3 has been widely used for the simulation of wireless networks, because it features several built-in and external modules implementing different wireless technologies. The overall performance of this kind of networks are strongly influenced by the characteristics of the signal propagation through the wireless link, thereby, a proper modeling of the channel behavior is of primary importance to obtain reliable results from the simulations. This project aims to tackle this issue by proposing an extension of the spectrum module to model both frequency and spatial-dependent phenomena, and to account for the directional behavior of the signal propagation. This will be achieved by implementing the modeling framework described in 3GPP TR 38.901, which includes the statistical characterization of different propagation environments, supports the modeling of multi-antenna systems, and, thanks to its modularity, can be easily extended with new environments or other additional features. Even if it has been specifically designed for the simulation of cellular networks, it supports frequency bands between 0.5 and 100 GHz, thus can be used even for other wireless technologies.