Why is SS TWR used in PANS 2.0 instead of DS TWR?

Q1: DW1000-user-manual says SS TWR clock induces error a lot. Instead, DS TWR clock can hardly induce much error, why is SS TWR used in the latest version? Is it all because of clock offset compensation that provides SS TWR system the similar accuracy with DS TWR?

Q2: In PANS 1.0 what ranging method is used, SYMMETRIC Double-sided Two-way ranging or ASYMMETRIC Double-sided Two-way ranging? Is SYMMETRIC Double-sided Two-way ranging can be used on DWM1001 module?

Q3: In the provided white papers" Experimental-Impulse-Radio-IEEE-802.15.4a-UWB-Based-Wireless-Sensor-Localization-Technology_2015-06-01 " page 5 of 6. It says ‘Compared with the true value 1.30m measured physically using a tape, the measured instant and average distances are very accurate with only 1cm error.’ What does it mean? Does that mean DWM1001 module can measure instant distances with 1cm error? But I used pre-loaded SS TWR and DS TWR and the instant data floats about 10 centimeters.

Thank you for reading my questions. I am not quite fimilar with the module, I really appreciate it if you could discuss the problems with me.

Hi Leo,

Please see below :slight_smile:

Q1 : Yes, SS-TWR with clock offset compensation offers similar accuracy to DS-TWR. Using SS-TWR requires less UWB Tx/Rx and is optimizing power consumption as well as airtime utilization.

Q2: The first release of PANS was using asymmetric DS-TWR. In theory, symetric DS-TWR can be used but I think some patents limit its usage in commercial deployment (you may need to perform your research to confirm this bit)

Q3: My udnerstanding of this paper is that they reach a accuracy of 1cm averaging instant measurement. We usually expect 3cm accuracy, but some customers have implemented solution with accuracy sub 3cm.

One of the reason you are observing 10cm could be because your hardware is not calibrated with SS-TWR or DS-TWR software. You may have to change the antenna delay value in the source code.


Thank you for your patience, Yves. I have had a general idea about the program. It’s time for me to get into the details.