Not my tutorial or a code stack I’ve used but I can give some answers.
- From the context one session in this instance would be one set of ranging messages, the minimum message group required to calculate ranges.
- Length would depend on the details of the protocol used (the data rate used, the preamble length used, the data packet sizes, the periods between them). If you need to be compatible with external devices then these may be fixed, if you only need to be compatible with your own equipment and have the full source code then you can vary them.
- Again depends on what you need to be compatible with. The basic concept will support as many responders as you like but this would increase the session time and so decrease the update rate. Also longer time periods give more time for clocks to drift and things to move (most systems work on the assumption the range is constant during the measurement time) so there is a trade off to make.
- See 3.
To give you an idea I have a system using DW1000/DW3000 that is fully custom, I didn’t worry about supporting any other equipment or being compatible with any other standards other than the basic UWB transmission frame. It can range to either 8 responders at 300 Hz or 12 responders at 200 Hz so session times or 3.3 ms or 5 ms. I find these numbers to give the best compromise between update rate and accuracy. This is a system designed from the ground up for speed of range measurement and makes other compromises to get there so update rates will be slower on more generic systems.
More responders would add a lot of cost in having enough extra responders in range to be of benefit. Less would degrade the position accuracy and make drop outs more likely since you have less redundancy.