Propagation History
- Since its early days as part of the Central Radio Propagation Laboratory (CRPL), ITS has been deeply involved in research on how radio ways travel from one point to another. Past work has included the development of the radio wave propagation models that are now used in frequency ranges from the lowest to the highest.User-Friendly Propagation Models - Models showing the statistical dependence of path loss on terrain and distance, ionospheric conditions, and atmospheric humidity and precipitation have been developed and captured in elaborate computer models. Much recent ITS work has included modifying these existing models and data bases to be more easily available on desktop computers so that they can be easily applied to user design problems.
Shortpath Model Development for PCS and Wireless LANs - New ITS propagation research includes short-path propagation modeling, applicable to proposed personal communications systems (PCS) and wireless LANs. These models must account for the effects of near-by reflectors and absorbers in short signal paths that include indoor and outdoors segments. Building penetration losses from interior and exterior walls and floors, as well as reflections which produce multipath cancellation and reinforcement are important factors.
ITS work includes a rapidly-growing program of measurements, modeling, and theoretical predictions. We would like to see this work result in a series of models that will allow accurate prediction of coverage within buildings and in outdoor urban environments. These programs will be suitable for design and placement of PCS radio ports, as well as helping to answer frequency planning questions on band sharing and allocations.
Wideband Communication Propagation Modeling - Reflections from obstacles not in the direct path between the transmitter and receiver create multiple copies of the radio signal that arrive at slightly delayed times and interfere with the direct path signal. This is a particular problem for wideband digital signals like HDTV. ITS has measured VHF and UHF propagation using a pseudo-noise probe signal broadcast from existing TV transmitters. Additional multipath measurements are underway in PCS environments and in the millimeter wave frequency bands.
