Gsm network interfaces
As defined in the system architecture of GSM each interface between the different elements of the GSM network is also defined. It facilitates the information interchanges can take place.
Network Interfaces: The following are the different interfaces for GSM:
- Um interface: The "air" or radio interface standard that is used for exchanges between a mobile (ME) and a base station (BTS / BSC).
- Abis interface: This is a BSS internal interface linking the BSC and a BTS, and it has not been totally standardized. The Abis interface allows control of the radio equipment and radio frequency allocation in the BTS.
- A interface: The A interface is used to provide communication between the BSS and the MSC.
- B interface: The B interface exists between the MSC and the VLR. It uses a protocol known as the MAP/B protocol. As most VLRs are collocated with an MSC, this makes the interface purely an "internal" interface.
- C interface: The C interface is located between the HLR and a GMSC or a SMS-G. When a call originates from outside the network, i.e. from the PSTN or another mobile network it has to pass through the gateway so that routing information required to complete the call may be gained.
- D interface: The D interface is situated between the VLR and HLR. It uses the MAP/D protocol to exchange the data related to the location of the ME and to the management of the subscriber.
- E interface: The E interface provides communication between two MSCs. The E interface exchanges data related to handover between the anchor and relay MSCs using the MAP/E protocol.
- F interface: The F interface is used between an MSC and EIR. It uses the MAP/F protocol. The communications along this interface are used to confirm the status of the IMEI of the ME gaining access to the network.
- G interface: The G interface interconnects two VLRs of different MSCs and uses the MAP/G protocol to transfer subscriber information, during e.g. a location update procedure.
- H interface The H interface exists between the MSC the SMS-G. It transfers short messages and uses the MAP/H protocol.
- I interface: The I interface can be found between the MSC and the ME. Messages exchanged over the I interface are relayed transparently through the BSS.
Figure : GSM interfaces