Satellite Navigation Rural Channel Model

Realistic channel models are essential for developing and testing new GPS and Galileo receiver algorithms. The dominant error source for land-mobile users is multipath reception. That is why our focus is to accurately model the multipath propagation channel for Global Navigation Satellite Systems (GNSS).

Based on a comprehensive measurement campaigns, we already developed GNSS channel models for urban, sub-urban, and aeronautical scenarios.

Currently, measurement data which was recorded during a Zeppelin-to-vehicle measurement campaing in rural settings is being processed. The resulting GNSS Rural Channel Model will simulate wave propagation effects caused by characteristic features found in rural areas. These effects include scattering and diffraction induced by trees, alleys, and utility poles for instance. It is planned that the user can define a scenery with trees and other features as well as a vehicle speed and satellite position. Based on the defined geometries the model will then output channel impulse reponses which can be used in GNSS simulation programs.

The movie below shows wave reflection and scattering by free-standing trees which was taped during the measurement campaign. The transmitter was installed on board of a Zeppelin and a van served as receiving platform.

This table explains the four clips shown in the movie:

The upper left clip shows the front camera which was built into the van. The Zeppeling is located behind the shown detail. That is, the van is driving away from the Zeppelin.

The upper right clip shows a possible visualization of the GNSS Rural Channel Model to be developed.

The van is represented by a yellow box with the antenna on top. The solid red bar is the LOS signal.

The lower left picture shows the measured channel impulse responses. The x-axis displays the delay in ns whereas the y-axis shows the ongoing time in seconds. The received power is coded as color: Red represents a strong signal and blue a weak one. The line-of-sight (LOS) path can be seen as solid red line at a delay of 0 ns.

You can see the reflections by approaching trees as thin cyan lines which wander from the right side (large delays) to the left side (smaller delays). When the van gets closer and closer to the tree, the reflected signal gets broader until it merges with the LOS signal.

The lower right picture shows the scattering function dependent on delay (x-axis, in ns) and Doppler frequency (y-axis, in Hz). The LOS signal can be seen as strong red signal at a delay of 0 ns with negative Doppler because the van is driving away from the Zeppelin.

Approaching trees and utility poles appear as small patches with positive Doppler which come closer until the van reaches them.