Intefaces among Mobile Network

What is Interface ?
            They are required to connect different nodes in the GSM network.

Types of Interfaces :-

• Air interface or Um-interface -  

 The Air Interface is the interface between the BTS (Base Transceiver Station) and the MS (Mobile Station).
The air interface is required for supporting:
- Universal use of any compatible mobile station in a GSM network.
- A maximum spectral efficiency.

• Abis-interface -

Its the interface between the BSC (Base Station Controller) and the BTS. The interface comprises traffic and control channels.
Functions implemented at the Abis-interface are:
- Voice-data traffic exchange.
- Signaling exchange between the BSC and the BTS.
- Transporting synchronization information from the BSC to the BTS.

• A-interface -

Its the interface between the BSS and the MSC. It manages the allocation of suitable radio resources to the MSs and mobility management.

• B-interface -

This interface is between between the MSC and the VLR.
VLR uses the MAP/B protocol. Most MSCs are associated with a VLR, making the B interface "internal". Whenever the MSC needs access to data regarding a MS located in its area, it interrogates the VLR using the MAP/B protocol over the B interface.

• C-interface -

It is between the HLR and a GMSC or a SMS-G.

Each call originating outside of GSM (i.e., a MS terminating call from the PSTN) has to go through a Gateway to obtain the routing information required to complete the call, and the MAP/C protocol over the C interface is used for this purpose.

• D-interface -

The D interface is between the VLR and HLR,
It uses the MAP/D protocol to exchange the data related to the location of the MS and to the management of the subscriber.

• E-interface -

It interconnects two MSCs.
The E interface exchanges data related to handover between the anchor and relay MSCs using the MAP/E protocol.

• F-interface -

It connects the MSC to the EIR (Equipment Identity Register),
It uses the MAP/F protocol to verify the status of the IMEI that the MSC has retrieved from the MS.

• G-interface -

The G interface interconnects two VLRs of different MSCs
It uses the MAP/G protocol to transfer subscriber information, e.g. during a location update procedure.

• H-interface -

The H interface is between the MSC and the SMS-G,
It uses the MAP/H protocol to support the transfer of short messages.

• I-interface -

It is the interface between the MSC and the MS.
Messages exchanged over the I interface are relayed transparently through the BSS.


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