Propagation models for mobile terrestrial VHF communications

A family of propagation models for the tactical VHF radio channel is presented based on propagation measurements conducted under the conditions expected for mobile land-tactical communications. The appropriate configuration for tactical communications is transmit and receive antennas on vehicular rooftops, or on backpacks, with mobile platforms. The phenomena modelled are multipath group and delay structure, and probability distribution of the multipath group attenuations. Models are given for different terrain environments: rural, suburban, littoral, and urban, and the results are specifically optimized to the operating frequencies within this band. The models are presented in a manner making them easy to implement in software or hardware for simulation or emulation. Because the wavelength varies by several factors over this band, the propagation is observed to be highly dependent on the frequency of operation. For example, at 30 MHz the wavelength of 10 metres is large as compared with many structures facing the propagating wave, while at 100 MHz, the wavelength of 3 metres is more comparable the size of ground-based structures in many environments, and subject to reflection and diffraction. The terrestrial propagation environment is therefore nonhomogeneous over this band, and models presented in this paper are frequency-dependent, thereby taking this into account.