Signal Loss and Poor Accuracy with MDEK1001 UWB System

[SARAH1]

Hello everyone,

I am working on a project using the Decawave MDEK1001 UWB system for positioning. My setup consists of three anchors and one tag, as shown in the attached diagram. The tag moves in all axes during testing.

I am experiencing two major issues:

1. Signal loss when the tag is close to the anchors:

• When the tag is near the anchors (within ~10-20 cm), I get a lot of missing data (NaN values) in my CSV logs.
• The signal seems to cut off frequently, making tracking unreliable.

2. Poor accuracy when the tag is farther away (~60 cm or more):

• When I increase the distance between the tag and anchors (~60 cm or more), the system works but with poor accuracy.
• The estimated positions fluctuate significantly compared to the actual position.

I would like to understand:

• Why is there significant signal loss when the tag is near the anchors?
• Why is the accuracy poor when the tag moves farther away?
• What are the best practices or solutions to improve both reliability and precision?

Thanks in advance

[AndyA]

Your accuracy is suffering because you have a poor geometry.

There is a concept used in GPS called Geometric Dilution of Precision or GDoP. The same concept also applies in UWB. The exact maths gets complicated but the basic idea is simple:

If all your measurements are in roughly the same direction then a small error in measurement will result in a large error in position. If your measurements are in a geometrically diverse set of directions then the same errors will result in a far smaller position error.

All your anchors are close to each other. As you move away from the anchors the range measurement errors remain the same but the GDoP gets worse, the difference in angle between the anchors decreases, so to accuracy decreases.
If you want good accuracy you need to place anchors such that the tag is within the volume contained between the anchors.