Rala,
PCH load and SDCCH load… it’s not related, theoretically. Those are two distinct physical channels, carrying data from different processes (Paging : broadcasted DL “ping” of a subscriber, SDCCH : dedicated channel for call setup, LU, SMS, etc.).
I can imagine that if the BTS has an overloaded CPU, because it’s trying to manage too many pagings, it might delay all processes including the SDCCH phase.
any other idea why ??