Reasons for carrier overlaps

Design and Planning
1

Hi All, one question:

Assume on a TDD band.
Carrier have 40 MHz so could have 2x20 carrier.

During planning one carrier overlaps with 200 kHz of other carrier for example :

  • Carrier 1 EARFCN : 55342
  • Carrier 2 ERAFCN : 55540

What is reason of this 200 kHz overlap?
It assumes for Doppler or high distance scenarios?

2

From my knowledge in signal treatment, the 100 kHz is for the channel raster and the center frequency must be a multiple of 100 kHz.

3

But if it hasn’t 200 kHz overlap, channel raster is observed.

4

This is due to Nominal Channel Spacing.

Nominal Channel Spacing = [ ( BWch1 + BWch2 - 0.1 abs (BWch1-BWch2) ) / 0.6 ] * 0.3