Hi, I am totally new here and I am interested in documentation or something that describes how is the default ranging calculated between two dwm1000 modules. I say default since I assume that we are allowed to even develop our prefered ranging methodology. Is that true?
According to my intuition, at some point, the system has produced a signal-flight-time estimation and converts this time into a distance (given a light speed). Or maybe, more than one distances are considered/averaged for the final distance estimation. On the other side, I have also noticed that there is a calibration phase too, which affects the final results. How does this work exactly?
I ask because I am eventually interested in modelling (at some) level the likelihood of the ranging estimations, considering typical indoor environments and random module’s orientations. For example, assuming that I had a measurement (whether this is RSSI, Flight-Time, Distance, what so ever) what is the likelihood of having this measurement at some distance. In other words, I do not want a single (the best) ranging estimation, rather than a PDF. How should I approach this you suggest? (assume that I am able to get accurate ground truth regarding the true distances between the modules).
Hello gouz and vogong, welcome to the Decawave forum
Our MDEK1001 kit, which is our main demo board for the DWM1000 is pre-programmed with the PANS software. This is a RTLS system that uses TWR (To Way Ranging) to measure the distance between ancors and tags. You can read more about this in the system overview.
As you mentioned, the DWM1000 can also be programmed with your own firmware, allowing you to build your own ranging implementation, the dwm1001 examples, also based on TWR, can be used as a starting poin. Typically this would always be based on ToF (time of flight) of the radio signal since this is what UWB technology is most suitable for and what the DecaWave chips are designed for. Solutions based on signal strength would in theory also be possible, but it would not offer the same accuracy and multi-path resilience and the DW1000 chip would not offer much benefit.
We also have some solutions based on TDoA (Time Difference on Arrival), which also relies on ToF and we are working on some PDoA (Phase difference of Arrival) which allows to detect the direction a signal came from.
The calibration is mainly needed to account for antenna delays. This can vary slightly between different modules, so calibrating this can offer more performance. This is more important when using a chip-down approach iof using a module, since in this case the antenna is different and could have a totally different antenna delay.
An other thing that can be calibrated is the transmit power. There are legal limits regarding the transmit power, depending on the channel and the region. Different antennas or the use of a casing could reduce the actual transmit power of the device, in this case it might be beneficial to increase the transmit power to get a better range. It could also be only a certain channel is used or the device will only be use in a certain region, which could allow higher TX powers to be used. Alternatively, it is sometimes beneficial to reduce the TX power, and thus reducing power consumption, in situations where only a short range is required.
Please have a look at our Application Notes. I know it’s a lot of reading, but a lot of your questions are answered in detail there.