What is MAP (Mobile Application Part)

Technical details of the Mobile Application Part (MAP).

1. Overview:
   • The Mobile Application Part (MAP) is an SS7 (Signaling System No. 7) protocol.
   • It operates at the application layer and facilitates communication between various nodes within GSM (Global System for Mobile Communications), UMTS (Universal Mobile Telecommunications System), and GPRS (General Packet Radio Service) mobile core networks.
   • Its primary purpose is to enable these nodes to exchange information and provide services to users.
2. Key Functions and Facilities Provided by MAP:
   • Mobility Services:
     • Location Management: Supports roaming by managing user location information.
     • Authentication: Verifies user identity during network access.
     • Service Subscription Management: Handles user service profiles.
     • Fault Recovery: Ensures robustness and reliability.
   • Operation and Maintenance:
     • Subscriber Tracing: Helps track users for troubleshooting and monitoring.
     • IMSI Retrieval: Retrieves the International Mobile Subscriber Identity (IMSI) associated with a user.
     • Call Handling: Routes and manages calls during roaming.
     • Supplementary Services: Provides features like call waiting, call forwarding, etc.
   • Short Message Service (SMS):
     • MAP facilitates SMS communication by interacting with the Short Message Service Center (SMSC).
   • Packet Data Protocol (PDP) Services for GPRS:
     • Provides routing information for GPRS connections.
     • Ensures seamless data transfer over the packet-switched network.
   • Location Service Management:
     • Obtains the location of subscribers (e.g., for emergency services).
3. Published Specifications:
   • Originally defined by the GSM Association, MAP specifications are now controlled by ETSI/3GPP.
   • There are two versions of MAP, depending on the mobile network type:
     • MAP for GSM (prior to Release 4): Specified by 3GPP TS 09.02 (MAP v1, MAP v2).
     • MAP for UMTS (“3G”) and GSM (Release 99 and later): Specified by 3GPP TS 29.002 (MAP v3).
4. Implementation:
   • MAP is a Transaction Capabilities Application Part (TCAP) user.
   • It can be transported using traditional SS7 protocols or over IP using Transport Independent Signalling Connection Control Part (TI-SCCP) or SIGTRAN.
   • Notably, Yate provides a partial open-source implementation of MAP.
5. Signaling in Mobile Cellular Networks:
   • In GSM and UMTS networks, MAP is used for signaling.
   • Voice connections (Circuit Switched) and data connections (Packet Switched) rely on MAP.
   • Examples of interfaces transported over SS7 in the Mobile Switching Center (MSC) include:
     • B interface: Between MSC and Visitor Location Register (VLR) for internal communication.
     • C interface: MSC to Home Location Register (HLR) for subscriber-related messages.
     • D interface: For attaching to the CS network and location updates.
     • E interface: Inter-MSC handover.
     • F interface: Equipment identity checks.
     • H interface: Short Message Service (SMS) over CS.