Frequency response of the waveguide
Okay, I found the formula, because I did some research, so it is said that:


  "It can be shown that almost regardless of the details of the course
  of the channel characteristic - as long as its frequency response is
  equal to W - the effect of channel crossing is to widen the pulse
  width by time Δτ≈1 / W."


So that almost answers my question, the only problem I have is why Δτ is multiplied by two? Otherwise, it wouldn't match to my result. Can anyone know?