"This standard provides the specification for the interface which coincides with the Reference Point ""A"" defined in the TR45 Network Reference Model shown in [25] and with Reference point 48 as defined in the Network Reference Model shown in [28]. The scope of this standard includes the following topics: ? Descriptions of the specified functional capabilities that provide wireless telecommunications services across the A1 interface as defined in the TR45 Network Reference Model; ? Descriptions of the division of responsibility of the functions provided between the BS and the MSC@ without prescribing specific implementations; ? Descriptions of the A1 interface standard that support DS-41 [7] and cdma2000?1 systems. ? Descriptions of the specified functional capabilities that provide circuit services across the packet transport based MSCe-BS (A1p) and MGW-BS (A2p) interfaces as defined in the Network Reference Model shown in [28]. It should be noted that@ for a given call@ the transcoder may or may not be in the MGW or BS. This protocol definition is not limited by the location or existence of the transcoder in the bearer path. ? Descriptions of the division of responsibility of the functions provided between the BS and the MSCe and MGW without prescribing specific implementations. Purpose This document contains the message procedures@ bitmaps@ information elements@ and timers used to define the A1 and A1p interfaces. In this document@ ""MSC"" refers to either a circuit-switched MSC or a packet-based MSC emulator (MSCe). In situations where a statement applies to either the circuit-switched or packet-based MSC exclusively@ the type of MSC will be specifically identified (i.e. ""circuit-switched MSC"" or ""MSCe""). For signaling@ the term MSC refers to either a circuit-switched MSC or an MSCe. For bearer path@ the term MSC refers to either a circuit-switched MSC or a MGW. A1 messages are used by both the A1 and A1p interfaces except where indicated. 1 cdma2000? is the trademark for the technical nomenclature for certain specifications and standards of the Organizational Partners (OPs) of 3GPP2. When applied to goods and services@ the cdma2000? mark certifies their compliance with cdma2000? standards. Geographically (and as of the date of publication)@ cdma2000? is a registered trademark of the Telecommunications Industry Association (TIA-USA) in the United States."