Physics-based propagation models for channels involving mixed paths

Predicting the radio signal levels and coverage areas for information warfare system communication channels between base stations, vehicles and warfighters is a challenging problem. The channel may involve radio frequency interactions with hills, foliage, and buildings. The paths may involve long distances over hilly terrain or shorter distances involving interaction with urban building features. Many propagation paths may simultaneously involve hills, foliage, and urban areas. For example, a warfighter sheltered in a doorway in an urban area may need to communicate with a command station located in a rural forested area outside of the city. These mixed path links involving both urban (including indoor) features and rural (including foliage) terrain are beyond the capability of any existing physics-based propagation model. Currently available models are applicable to paths where both the transmitting and receiving antennas are located in an outdoor urban environment, or indoors, or in rural areas. Development of fast and reliable mixed-path models valid over a wide range of communication frequencies is important in order to provide channel characterizations for realistic situations. This development will by necessity bring together different types of models. Full wave models may be applied to predict the antenna pattern from an antenna on a vehicle or a warfighter crouched below a wall. Full wave models may also be used for propagation paths involving terrain or atmospheric effects. Parabolic equation models may also be applied for these situations. Ray-based models are needed for complex interactions with urban features and for indoor situations. All of these need to be combined in new ways in order to obtain accurate mixed-path radio propagation predictions.