Recently wireless Networks-on-Chip (WiNoCs) have been proposed to overcome the scalability and performance limitations of traditional multi-hop wired NoC architectures. However, the adaptation of wireless technology for on-chip communication is still in its infancy. Consequently, several challenges such as simulation and design tools that consider the technological constraints imposed by the wireless channel are yet to be addressed. To this end, in this paper, we propose and efficient channel model for WiNoCs which takes into account practical issues and constraints of the propagation medium, such as transmission frequency, operating temperature, ambient pressure and distance between the on-chip antennas. The proposed channel model demonstrates that total path loss of the wireless channel in WiNoCs suffers from not only dielectric propagation loss (DPL) but also molecular absorption attenuation (MAA) which reduces the reliability of the system.