Method for selecting rach in a cdma mobile communication system

A method selecting a RACH comprises determining an access service class (ASC) associated with a unique access class of a user equipment (UE) by analyzing a radio resource control (RRC) message received from a UTRAN (UMTS (Universal Mobile Telecommunication System) Terrestrial Radio Access Network); receiving mapping information from the UTRAN; analyzing ASCs and scrambling codes to be used for available RACHs associated with each of the ASCs based on the received mapping information; mapping the analyzed scrambling codes to scrambling code groups associated with the ASCs; selecting a scrambling code group associated with the determined ASC; and selecting one of the scrambling codes using a total number of the scrambling codes mapped to the selected scrambling code group and a unique identifier of the UE.