Architectural requirements
This document covers the architectural requirements for 3GPP systems based on UTRAN, E-UTRAN and Iu mode GERAN. In particular it details the high level requirements for the Circuit Switched (CS) Domain and the stage 2 procedures that span more than one domain/subsystem. The reference model to which these procedures apply can be found within TS 23.002 [1]. In addition, A mode to Iu mode handover for CS services is addressed. Detailed architectural requirements within the subsystems are contained within the remainder of the 23 series of specifications e.g. the requirements for the Packet Switched (PS) domain are contained within TS 23.060 [2], TS 23.401 [27] and the requirements for the Bearer Independent CS Core Network are contained in TS 23.205[14].