ghost rach will trigger allocation of an SDCCH at the BSC side.
the following msg will be sent over abis:
channel activation acknoledge
immediate assignment command
and finally, on the air interface : immediate assignment command, from BTS to the MS (on AGCH).
Ghost RACH increases AGCH load and increase the number of SDCCH allocated by BSC (after the channel required, the BSC books a SDCCH channel)
So ghost rach can also lead to SDCCH congestion.
NO impact on PCH.