GSM Interfaces are designed to get the interface connectivity from one node to another. Through GSM Interface protocol flow takes place.
The air interface is used for exchanges between a MS and a BSS. LAPDm, a modified version of the ISDN LAPD, is used for signaling.
This is a BSS internal interface that links the BSC and a BTS; it has not been standardized. The Abis interface allows control of radio equipment and radio frequency allocation in the BTS.
It is the interface between the BSS and the MSC. A inetrface manages the allocation of suitable radio resources to the MSs and mobility management. It uses the BSSAP protocols (BSSMAP and DTAP).
The B interface handles signaling between the MSC and the VLR. It uses the MAP/B protocol. Most MSCs are associated with a VLR, making the B interface “internal.” Whenever the MSC needs to access data regarding an MS that is located in its area, it interrogates the VLR using the MAP/B protocol over the B interface.
It is the interface is between the HLR and a GMSC or a SMSC. Each call that originates outside of GSM (such as an MS terminating call from the PSTN) must go through a gateway to obtain the routing information that is required to complete the call, and the MAP/C protocol over the C interface is used for this purpose. Also, the MSC can optionally forward billing information to the HLR after call clearing.
It is the interface is between the HLR and VLR, and uses the MAP/D protocol to exchange data related to the location of the MS and subsets of subscriber data.
It is the interface connects MSCs. The E interface exchanges data that is related to handover between the anchor and relay MSCs using the MAP/E protocol. The E interface can also be used to connect the GMSC to an SMSC.
It is the connects the MSC to the EIR and uses the MAP/F protocol to verify the status of the IMEI that the MSC has retrieved from the MS.
It is the inter face that connects two VLRs of different MSCs and uses the MAP/G protocol to transfer subscriber information—for example, during a location update procedure.
The H interface is located between the MSC and the SMSG and uses the MAP/H protocol to support the transfer of short messages. Again, GSM as well as ANSI-41 is unknown, but H in ANSI-41 is used for HLR–AC interface.
This Gb interface is located between BSC and SGSN. It ensures the transmission of GPRS Mobility Management (GMM) signalling and NM (Network Management) signalling. The peer-to-peer communication across the Gb interface between the two remote BSSGP entities in the BSS and the SGSN is performed over virtual connections.
Interface between the GGSN and the SGSN. The Gn interface is between two GSNs within the same public land mobile network (PLMN) in a GPRS/UMTS network. The Gp interface is between two GSNs in different PLMNs. GTP is a protocol defined on the Gn/Gp interface.
It is the between SGSN and MSC/VLR is used to perform paging request of circuit switched GSM call for combined attachment procedure.