Types Of Interfaces: 2G

Different Types of interfaces:

l   A interface

l   B interface

l   C interface

l   D interface

l   zz interface

l   39/xx interface

l   Q interface

l   T1 interface

l   ISUP interface

1. A Interface

The A interface exists between the circuit switched domain of the CDMA network subsystem (NSS) and the base station subsystem (BSS). In terms of entity, it is the interface between the MSCe/MGW and BSC.

The A interface complies with the base station subsystem application part (BSAP) of signaling system SS7. It includes voice channels and signaling channels. The A interface is used to transmit the following messages:

l   Mobile station (MS) management messages

l   Base station (BS) management messages

l   Mobility management messages

l   Call processing messages

2. B Interface

The B interface exists between MSCe and VLR. It adopts an internal protocol without a specific signaling transmission mode. The B interface is used in the following cases:

l   The MSCe obtains user messages from the VLR.

l   The MSCe notifies the VLR to record location information when an MS updates its location.

l   The MSCe notifies the HLR to update data through VLR when an MS activates a supplementary service or modifies the relevant data.

3. C Interface

The C interface exists between the MSCe and HLR. It complies with the mobile application part (MAP) of the SS7. The C interface is used in the following cases:

l   The HLR sends routing information to the MSCe when an MS is called.

l   The short message service (SMS) is implemented.

4. D Interface

The D interface exists between VLR and HLR. It complies with the MAP of the SS7. The D interface is used to transmit the following messages:

l   Authentication data

l   Location update messages

l   User data indexed during call connection

l   Data of supplementary services

l   VLR recovery messages

5. zz Interface

The zz interface exists between two MSCes. It complies with the SIP with encapsulated ISUP (SIPI).

The zz interface provides the inter-office call control function for the narrowband circuit-switched domain services that are independent of the user plane bearer technology and the control plane transmission technology.

6. 39/xx Interface

The 39/xx interface exists between an MGW and a media resource function processor (MRFP). It complies with the Megaco/H.248. The 39/xx interface is used in the following cases:

l   The MSCe controls dynamic and static resources of the transmission modes (IP/TDM) in the MGW during call processing, including terminal attributes, terminal connectivity, and media streams.

l   The MSCe maintains and manages the status of the MGW.

7. Q Interface

The Q interface exists between the MSCe and the MC. It complies with the MAP of the SS7 to support the short message service.

8. T1 Interface

The T1 interface exists between the MSCe and the SCP. It complies with the WIN of the SS7 to support the intelligent network service
9. ISUP Interface
When the MSC serves as a gateway office, it provides the interface between the PSTN and other mobile network devices. It also controls the incoming calls and outgoing calls through ISUP or TUP of the SS7