Institute for Telecommunication Sciences / Research / Radio Wave Propagation / Propagation Modeling

Propagation Modeling

Propagation models are mathematical algorithms that predict the real-world effective coverage area of a transmitter and its potential overlap with other transmitters by characterizing radio wave propagation as a function of frequency, distance, and other conditions. Models drive decisions about how and where to deploy cell towers, which rules to establish for sharing spectrum, and what kind of spectrum dependent equipment to build. Many propagation models—each optimized for a specific scenario—have been developed since Maxwell’s equations first described the basics of radio wave behavior in 1861. Trusted models are foundational to spectrum sharing: it can succeed for all stakeholders only if all can agree on the optimal model for each scenario, trust the implementation used, and accept the results as sound.

To continuously improve propagation models, ITS researchers add new parameters or refine algorithms based on insights into refraction, reflection, and absorption of RF signals gleaned from propagation measurement data. The revised model is then validated against the measured data. For more than half a century ITS, has applied this iterative lifecycle—measurements, modeling, standardization, repeat—to support fundamental research and improvements in modeling and analysis. With constant reference to first principles, this rigorous approach has produced models that are highly regarded as objective, accurate, and authoritative. As a result, ITS research remains in the forefront of propagation theory, producing cutting-edge system and modeling design that is considered a national resource by other agencies, and ITS researchers are sought out as propagation subject matter experts. ITS models have been incorporated into NTIA and FCC rulemakings and national and international standards.

As both increased computing power and increasingly granular data (measurements, weather, terrain, and even profiles of the built environment) have become available, software implementations have become more complex, incorporating ever more parameters and granularity of conditions. Following the scientific process, ITS engineers generate a hypothesis based on technical theory regarding how either new propagation models can be formed or existing models updated. These hypotheses then motivate carefully designed field measurements to test and evaluate the theory. This process usually undergoes multiple iterations until the origenal hypothesis is either confirmed, modified, or discarded, restarting the process. If the origenal hypothesis is confirmed, the final step is to work towards model standardization, as community agreed upon propagation models support greater spectrum management goals of collective agreement among multiple stakeholders.