Path Gain Comparison Near Longmont, Colorado

To validate MWFDTD over irregular terrain, results were compared to path gain measurements performed by the Institute for Telecommunication Sciences (ITS) in near Longmont, Colorado.

In addition to the ray-based Vertical Plane Propagation model, InSite can predict radio wave propagation using the optional Moving Window Finite-Difference Time-Domain propagation model (MWFDTD). Unlike ray-based techniques, MWFDTD simulates the radio wave propagation by using a modified FDTD method to directly solve Maxwell's equations. An FDTD grid moves along with the propagating pulse allowing calculations to be preformed for very long paths without requiring excessive amounts of memory often associated with FDTD approaches.

To validate MWFDTD over irregular terrain, results were compared to path gain measurements performed by the Institute for Telecommunication Sciences (ITS) in near Longmont , Colorado [1]. Measurements from various transmitting sites were taken by a common receiving tower. Path gain measurements and the latitude/longitude coordinates of the receiver and transmitters were obtained from the ITS website .

Project Set Up

The imported DTED terrain was assigned a relative permittivity of 4.0 and a conductivity of 0.001 S/m. After creating the terrain, transmitters and receivers can be placed in the project by entering their longitude and latitude coordinates and the transmitter's height above the terrain. All seven transmitters are located 6.6 meters above the ground, and the receiver tower extends vertically from ground level to 13 meters. Horizontally polarized isotropic antennas were assigned to both the transmitters and receiver, and a 410 MHz sinusoid was used to describe the waveform. The MWFDTD study area properties window is displayed in Figure 1. Figure 2 shows the imported terrain along with the transmitter and receiver locations in the Wireless InSite project. Path profiles are labeled above the transmitter locations in the figure.

For the selected paths, predictions from Wireless InSite's Moving Window FDTD model show good agreement with the ITS measurements.

References

  • [1] McQuate, P. L., J. M. Harman, and A. P. Barsis (1968),