MAP (Mobile Application Part)

MAP (Mobile Application Part):

MAP is the protocol is to used to allow the GSM network nodes within the NSS to communicate with the each other to provide the service, such as roaming, SMS, Subscriber authentication. MAP is transported and encapsulated with the SS7 protocols MTP, SCCP, and TCAP.

MAP Phase 2 operations can be divided into the following main categories:
• Mobility Management
• Operation and Maintenance
• Call Handling
• Supplementary Services
• Short Message Service

Mobility Management: 
Mobility management operations can be divided into the following categories:
• Location Management
• Paging and Search
• Access Management
• Handover
• Authentication Management
• Security Management
• IMEI Management
• Subscriber Management
• Identity Management
• Fault Recovery

Location Management:
To minimize transactions with the HLR, it only contains location information about the MSC/VLR to which the subscriber is attached.The VLR contains more detailed location information, such as the location area in which the subscriber is actually roaming. VLR requires that its location information be updated each time the subscriber changes location area.The HLR only requires its location information to be updated if the subscriber changes VLR.

Location management operations include the following:
• updateLocation - Message used by VLR to inform the HLR about change in VLR area.
• cancelLocation - The cancelLocation operation is used by HLR to delete a subscriber’s profile from the previous VLR
• sendIdentification  - the new VLR queries the old VLR using a sendIdentification operation to obtain authentication information. The sendIdentification operation sends the TMSI as its argument, and the result contains the IMSI and other authentication information (RAND, SRES, and optionally KC). If it is unable to obtain this information, it can retrieve the information from the HLR via a sendAuthenticationInfo operation.
• purgeMS - This message is sent if an MS has been inactive (no call or location update performed) for an extended period of time. The VLR sends this message to the HLR to indicate that it has deleted its data for that particular MS.

Handover:
The following sections describe MAP handover operations:
• prepareHandover - The prepareHandover message is used to carry a request and response between the two MSCs at the start of a basic inter-MSC handover
• sendEndSignal - Following a successful inter-MSC handover (from MSC-A to MSC-B in the case of a basic handover), MSC-B sends a sendEndSignal message to MSC-A to allow it to release its radio resources
• processAccessSignalling -
• forwardAccessSignalling
• prepareSubsequentHandover - If another inter-MSC is required (back to MSC-A or to another MSC, C), then MSC-B sends this message to MSC-A. It contains the information required for MSC-A to send a prepareHandover message to MSC-C

Authentication Management:
MAP operation sendIdentificationInfo is the only operation in Phase 2 that falls under the category of authentication management..

IMEI Management:
The only MAP operation in the IMEIs management category is checkIMEI, which is used to check whether a piece of mobile equipment is on a black, gray, or white list. the MSC sends the IMEI to the EIR in a MAP checkIMEI operation. The EIR checks the status of the IMEI and sends the result back to the MSC.

Subscriber Management:
An HLR uses subscriber management procedures to update a VLR with specific subscriber data when the subscriber’s profile is modified. A subscriber’s profile can be modified, because the operator has changed the subscription of the subscriber’s basic services or one or more supplementary services.

- insertSubscriberData: The HLR uses the insertSubscriberData operation to provide the VLR with the current subscriber profile
- deleteSubscriberData: The HLR uses the deleteSubscriberData operation to inform the VLR that a service has been removed from the subscriber profile.

 - restoreData: When a VLR receives a provideRoamingNumber request from the HLR for either an IMSI
that is unknown to the VLR or an IMSI in which the VLR entry is unreliable because of an HLR outage, the VLR sends a restoreData message to the HLR to synchronize the data.

Call Handling:
Call handling does not have subcategories of operations; it simply has the following two operations:
• sendRoutingInfo - The GMSC then identifies the subscriber’s HLR based on the MSISDN, and invokes the MAP operation sendRoutingInformation with the MSISDN as a parameter towards the HLR to find out where the MS is presently located.
• provideRoamingNumber - Because of past location updates, the HLR already knows the VLR that currently serves the subscriber. To obtain a mobile station roaming number (MSRN), the HLR queries the VLR using the operation provideRoamingNumber with the IMSI as a parameter. The VLR assigns an MSRN from a pool of available numbers and sends the MSRN back to the HLR in an acknowledgement.

Supplementary Services:
 Supplementary services includes the following operations:
• registerSS - The registerSS operation is used to register a supplementary service for a particular subscriber.
• eraseSS - EraseSS is used to delete a supplementary service that was entered for a particular subscriber using registerSS.
• activateSS - ActivateSS is used to activate a supplementary service for a particular subscriber.
• deactivateSS - This operation switches off a supplementary service for a particular subscriber;
• interrogateSS - InterogateSS allows the state of a single supplementary service to be queried for a particular subscriber in the HLR.
• registerPassword - This operation is used to create or change a password for a supplementary service. When the HLR receives this message, it responds with a getPassword message to request the old password,
• getPassword - The HLR sends this message if the subscriber wants to change his current password or modify or activate a supplementary service.

Unstructured Supplementary Services (USSs):
USSs allow PLMN operators to define operator-specific supplementary services and to deliver them to market quickly. The communication is carried out using Unstructured supplementary service data (USSD)
data packets,Unlike SMS, which is based on a store and forward mechanism, USSD is session oriented and, therefore, has a faster turnaround and response time than SMS, which is particularly beneficial for interactive applications. USSD can carry out the same two-way transaction up to seven times more quickly than SMS can.

Short Message Service (SMS): It has the following operations:
• forwardSM
• sendRoutingInfoForSM
• reportSMDeliveryStatus
• readyForSM
• alertServiceCentre
• informServiceCentre