The Mobile Application Part (MAP) is an SS7 protocol which provides an application layer for the various nodes in GSM and UMTS mobile core networks

Network Switching Subsystem

Network switching subsystem is the component of a GSM system that carries out call switching and mobility management functions for mobile phones roaming on the network of base stations...

 and GPRS core networks

GPRS Core Network

The GPRS core network is the central part of the General Packet Radio Service which allows 2G, 3G and WCDMA mobile networks to transmit IP packets to external networks such as the Internet...

 to communicate with each other in order to provide services to mobile phone

Mobile phone

A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

 users. The Mobile Application Part is the application-layer protocol used to access the Home Location Register, Visitor Location Register, Mobile Switching Center, Equipment Identity Register, Authentication Centre, Short message service center

Short message service center

A short message service center is a network element in the mobile telephone network which delivers SMS messages.-Operation:When a user sends a text message to another user, the message gets stored in the SMSC which delivers it to the destination user when they are available...

 and Serving GPRS Support Node (SGSN).

Facilities provided

The primary facilities provided by MAP are:

• Mobility Services: location management (roaming
  Roaming
  In wireless telecommunications, roaming is a general term referring to the extension of connectivity service in a location that is different from the home location where the service was registered. Roaming ensures that the wireless device is kept connected to the network, without losing the...
  
  ), authentication, managing service subscription information, fault recovery,
• Operation and Maintenance: subscriber tracing, retrieving a subscriber's IMSI
• Call Handling: routing, managing calls whilst roaming, checking that a subscriber is available to receive calls
• Supplementary Services
• Short Message Service
  Short message service
  Short Message Service is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices...
  
  
• Packet Data Protocol (PDP) services for GPRS: providing routing information for GPRS connections
• Location Service Management Services: obtaining the location of subscribers

Published specification

The Mobile Application Part specifications were originally defined by the GSM Association, but are now controlled by ETSI/3GPP

3GPP

The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

. MAP is defined by two different standards, depending upon the mobile network type:

• MAP for GSM (prior to Release 4) is specified by 3GPP TS 09.02
• MAP for UMTS ("3G") and GSM (Release 99 and later) is specified by 3GPP TS 29.002

Implementation

MAP is a Transaction Capabilities Application Part

Transaction Capabilities Application Part

Transaction Capabilities Application Part, from ITU-T recommendations Q.771-Q.775 or ANSI T1.114 is a protocol for Signalling System 7 networks. Its primary purpose is to facilitate multiple concurrent dialogs between the same sub-systems on the same machines, using Transaction IDs to differentiate...

 (TCAP) user, and as such can be transported using 'traditional' SS7 protocols or over IP

Internet Protocol

The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...

 using Transport Independent Signalling Connection Control Part (TI-SCCP); or using SIGTRAN

SIGTRAN

SIGTRAN is the name, derived from signaling transport, of the former Internet Engineering Task Force working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for Signaling System 7 and ISDN communications protocols....

.

MAP Signaling

In mobile cellular telephony networks like GSM and UMTS the SS7 application MAP is used. Voice connections are Circuit Switched

Circuit switching

Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...

 (CS) and data connections are Packet Switched

Packet switching

Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...

 (PS) applications.

Some of the GSM/UMTS Circuit Switched interfaces in the Mobile Switching Center (MSC) transported over SS7 include the following:

B -> VLR (uses MAP/B). Most MSCs are associated with a Visitor Location Register (VLR), making the B interface "internal".

C -> HLR (uses MAP/C) Messages between MSC to HLR handled by C Interface

D -> HLR (uses MAP/D) for attaching to the CS network and location update

E -> MSC (uses MAP/E) for inter-MSC handover

F -> EIR (uses MAP/F) for equipment identity check

H -> SMS-G (uses MAP/H) for Short Message Service

Short message service

Short Message Service is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices...

 (SMS) over CS
There are also several GSM/UMTS PS interfaces in the Serving GPRS Support Node (SGSN) transported over SS7:

Gr -> HLR for attaching to the PS network and location update

Gd -> SMS-C for SMS over PS

Gs -> MSC for combined CS+PS signaling over PS

Ge -> Charging for Customised Applications for Mobile networks Enhanced Logic

Customised Applications for Mobile networks Enhanced Logic

Customised Applications for Mobile networks Enhanced Logic, or CAMEL for short, is a set of standards designed to work on either a GSM core network or UMTS network. They allow an operator to define services over and above standard GSM services/UMTS services...

(CAMEL) prepaid charging

Gf -> EIR for equipment identity check