GSM Network Signaling

GSM Network Signaling

September 30, 2005 Girish Kumar Patnaik 2

GSM Protocol Interfaces


GSM Protocol Interfaces


GSM Protocol Interfaces• GSM MAP (Mobile Application Part)

– Software platform for implementing the GSM network signaling protocol

– Used in the B, C, D, E, F and G interfaces– In terms of network signaling, GSM architecture

can be partitioned into three parts:• Databases• Switches• Radio System

– Application of the SS7 protocol


GSM MAP Protocol Hierarchy


GSM MAP Protocol Hierarchy• Message Transfer Part (MTP)

– Level 1 defines the physical, electrical and functional characteristics of the signaling links

– Level 2 provides reliable transfer of signaling messages between two directly connected signaling points

– Level 3 provides the function and procedures related to message routing and network management

• Signaling Connection Control Part (SCCP)– Provides additional functions such as Global Title

Translation (GTT) to the MTP– MTP utilizes GTT to transfer noncircuit-related signaling

information such as PCS registration and cancellation


GSM MAP Protocol Hierarchy• Signaling Connection Control Part (SCCP)

– GSM MAP uses SCCP classes 0 and 1 connectionless services that provide efficient routing with or without maintaining message sequencing between two or more messages

– Network entities may consists of several Application Service Elements (ASEs)

– SCCP addresses these ASEs with Subsystem Number (SSN)

– For Intra-GSM network message delivery, MTP uses Destination Point Code (DPC) as the destination address for direct routing

– For Inter-GSM network message delivery, SCCP translates the actual destination address by GTT


GSM MAP Protocol Hierarchy• Transaction Capabilities Application Part

(TCAP)– Provides the capability to exchange information

between applications using noncircuit-related signaling


GSM MAP Service Framework

• The GSM network entities (such as HLR, VLR, and MSC) communicate with each other through MAP dialogues by invoking MAP service primitives.– Request– Indication– Response– Confirm


GSM MAP Service Model


Parameter of Service Primitive• The parameter of a service primitive type

belongs to the four categories:– M (Mandatory)– O (Service provider option)– U (Service user option)– C (Conditional)


MAP Services• A MAP dialogue consists of several MAP

services.• MAP services are either specific or common.• MAP services are specific:

– The specific MAP service includes• 28 mobility services• 4 operation and maintenance services• 6 call-handling services• 11 supplementary services• 8 short message service management services


MAP Services• MAP services are common:

– To establish and clear MAP dialogue between peer MAP service users.

– Six common MAP services are defined:• MAP-OPEN, MAP-CLOSE, MAP-DELIMITER,

MAP-U-ABORT, MAP-P-ABORT, MAP-NOTICE


The MAP Protocol Machine• When a MAP user issues a service request, the

request is processed by the MAP Protocol Machine (PM) in the service provider.

• MAP PM consists of four components:– Dialogue State Machine (DSM)

• Co-ordinates the service state machines (SSMs)• For every MAP dialogue, an instance of DSM is created

to handle the dialogue• An SSM is either an RSM or a PSM


The MAP Protocol Machine– Requesting Service State Machine (RSM)

• Handles a MAP-specific service requested during a dialogue

• This SSM is created by the DSM for each requested service

– Performing Service State Machine (PSM)• Handles a MAP service performed during a dialogue• This SSM is created by the DSM for each service to be

performed


The MAP Protocol Machine– Load Control

• Monitors the traffic generated by the service activities• There is only one instance of this process in each system• If an overload situation is detected, low-priority MAP

operations may be ignored• Priority levels from high to low for MAP service

primitives are Handoff, Mobility Management, Short Message Services, Subscriber-controlled inputs (call waiting, call forwarding)


The MAP Protocol Machine


The MAP Protocol Machine• When the service provider receives a MAP-OPEN

request from the service user or a TC-BEGIN Indication from the TCAP, the MAP PM is invoked and an instance of DSM is created.

• For every service primitive issued during the MAP dialogue, an instance of PSM is created by the DSM at the performer’s side, and an instance of RSM is created by the DSM at the initiator’s side.


MAP Dialogue


Acknowledgement• Slides obtained from home page of

Prof.Phone Lin • Slides obtained from home page of

Prof.Gerald Q. Maguire Jr.

Documents

GSM Network Signaling