SS7 Protocol and GSM network

SS7 Protocol and GSM network

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Done by : Thuraya Bani Yaseen

Supervisor : Globitel Company

SS7 or Signaling System Number 7 : describe a means of communication between telephone switches in public telephone networks

SS7 protocol

Physical Layer (MTP-1)

MTP-1

This defines the physical and electrical characteristics of the signaling links of the SS7 network. Signaling links utilize DS–0 channels and carry raw signaling data at a rate of 56 kbps or 64 kbps (56 kbps is the more common implementation).

Message Transfer Part—Level 2 (MTP-2)

MTP-2

provides link-layer functionality. It ensures that the two end points of a signaling link can reliably exchange signaling messages. It incorporates such capabilities as error checking, flow control, and sequence checking

Message Transfer Part—Level 3 (MTP-3)

MTP-3

extends the functionality provided by MTP level 2 to provide network layer functionality. It ensures that messages can be delivered between signaling points across the SS7 network regardless of whether they are directly connected. It includes such capabilities as node addressing, routing, alternate routing, and congestion control.

Signaling Connection Control Part (SCCP)

SCCP

provides connectionless and connection-oriented network services and global title translation (GTT) capabilities above MTP Level 3. SCCP is used as the transport layer for TCAP-based services. It offers both Class 0 (Basic) and Class 1 (Sequenced) connectionless services. SCCP also provides Class 2 (connection oriented) services, which are typically used by Base Station System Application Part, Location Services Extension (BSSAP-LE). In addition, SCCP provides Global Title Translation (GTT) functionality.

Transaction Capabilities Application Part (TCAP)

TCAP

TCAP defines the messages and protocol used to communicate between applications (deployed as subsystems) in nodes. It is used for database services such as calling card, 800, and AIN as well as switch-to-switch services including repeat dialing and call return. Because TCAP messages must be delivered to individual applications within the nodes they address, they use the SCCP for transport.

Mobile Application Part (MAP)

MAP

messages sent between mobile switches and databases to support user authentication, equipment identification, and roaming are carried by TCAP.

* Mechanism for a Gateway-MSC (GMSC) to obtain a routing number for an incoming call

* Mechanism for an MSC via integrated Visitor Location Register (VLR) to update subscriber status and routing number.

* Subscriber CAMEL trigger data to switching elements via the VLR

* Subscriber supplementary service profile and data to switching elements via the VLR.

Intelligent Network Application Part

enable the communication between network elements (such as SSPs and SCPs) that is needed to implement services

INAP

ISDN User Part (ISUP)

defines the messages and protocol used in the establishment and tear down of voice and data calls over the public switched network (PSN), and to manage the trunk network on which they rely. Despite its name, ISUP is used for both ISDN and non–ISDN calls. In the North American version of SS7, ISUP messages rely exclusively on MTP to transport messages between concerned nodes.

ISUP

The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets.

GSM network

Mobile Switching Center

MSC

1)Switching, controlling, and logging calls

2)Interface with PSTN, ISDN, etc.

3) Mobility management over the radio network and other Networks

4) Radio Resource management such as handovers between BSC’s

5) Logging and providing billing Information

Visitor Location Registry

VLR

The VLR stores temporarily information about the MS’s served by the MSC such as:

 1)The IMSI

 2)The MS ISDN Number

 3)The MS Roaming Number

4) The location area (i.e.; BTS, BSC, etc.), where MS has been registered

 5)Supplementary service parameters such as call forwarding, caller ID, etc

Short Message Service Center (SMSC)

1)Reception of text messages (SMS) from wireless network users

2)Storage of text messages

3)Forwarding of text messages

4)Delivery of text messages (SMS) to wireless network users

5)determines whether a given recipient is available on the network. If so, the message is sent. Otherwise, it is stored until the intended recipient becomes available.

SMSC

Equipment Identity Registry

1) The EIR is a database that stores the unique IMEI

number of each MS in the network

2) The EIR controls access to the network by returning the

status of an MS in response to an IMEI query

EIR

Home Location Registry

HLR

1) The HLR stores the MSC/VLR that the MS is currently registered

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2) The HLR stores details about all MS’s in the network, such as:

* Location information: MS roaming number, VLR, MSC

* International Mobile Subscriber Identity (IMSI)

* MS ISDN number

* Service restrictions

*Supplementary services

1) http://www.telecomspace.com/ss7.html

2) Dr. Fahed H. Awad

References