Several questions about the channel impulse response (Unit/Noise/Blank space)

Hi everyone,

I took the channel impulse response (CIR), generated by the preamble and I have some questions about it.
Attached is the figure of the absolute value of the CIR.

  1. What is the blank space in the CIR? Is this some sort of reset? Or did I miss some values?
  2. Which unit does the figure actually have?
  3. Is there some way to get the noise level from this plot. I understand that due to the accumulation the noise gets less, therefore it seems not so straightforward. Or is there any other way to get the noise level? I know that the DW1000 model offered the possibility to read the noise level. Is there something similar for the DW3000 and if not, why so?

Kind regards.