BY KAMAL RAJ SINGH ID : 2009H124492P M.E. COMMUNICATION ENGG.

Contents  Types of Signaling  SS7 Signaling  SS7 Protocol Architecture  The SS7 User Part  Signaling Traffic in SS7  SS7 Services

Types of Signaling Signaling in Telecommunications Network  Channel Associated Signaling (CAS)  Common Channel Signaling (CCS) Channel Associated Signaling (CAS) :-  Used for In-Band Signaling.  Signaling is transmitted in the same frequency band as used by voice. Common Channel Signaling (CCS):-  Out of Band signaling  Employs separate, dedicated path for signaling.  Voice trunks are used only when a connection is established, not before.  Faster Call Setup.  Signaling System Number (SS7) is a form of Common Channel Signaling  SS7 protocol used by the telephone companies for interoffice signaling

SS7 Protocol Architecture OSISS7

The SS7 User Part: Provides call control and management function and call set-up capabilities to the network. These higher layers in the SS7 utilize the transport facility provided by MTP(Message transfer part) and SCCP (signaling connection control part) ISDN User Part (ISUP)  Used to set up telephone calls in PSTN  When a telephone call is set up from one subscriber to another, many telephone exchanges will be involved, possibly across international boundaries.  To allow a call to be set up correctly, where ISUP is supported, a switch will signal call-related information to the next switch in the network using ISUP messages.  The telephone exchanges are connected via trunks which transport the speech from the calls.

…  These trunks are divided into 64 Kbit/s timeslots, and one timeslot can carry exactly one call.  Each timeslot between two switches is uniquely identified by a Circuit Identification Code (CIC) that is included in the ISUP messages.  The exchange uses this information along with the received signaling information (especially the Called Party Number) to determine which inbound CICs and outbound CICs should be connected together to provide an end to end speech path.

… Transaction Capabilities Applications Part (TCAP)  Its primary purpose is to facilitate multiple concurrent dialogs between the same sub-systems on the same machines, using Transaction IDs to differentiate these, similar to the way TCP ports facilitate multiplexing connections between the same IP addresses on the Internet.  TCAP messages are sent over the wire between machines. Operation Maintenance and Administration part (OMAP)  OMAP is a TCAP application for network management i.e. monitoring,coordination and control function for trouble free communication

Signaling Traffic in SS7  Maximum signaling traffic in a network is generated by Call set- ups, inter-MSC handoffs and location update  Setting up of a call requires exchange of information about the location of calling subscriber and information about the location about the called subscriber  Either one or both subscriber can be mobile  When any of mobile subscriber switches MSCs under a handoff condition, it adds to the amount of information exchanged  Location update records are updated in the network whenever a subscriber moves to a new location

Signaling Load For a Call setup and Handoffs in GSM Call originating from a mobileLoad Information on originating MSC and the terminating switch 120 bytes Information on the originating MSC and the associated VLR 550 bytes Call terminating at a mobile Information on the switch and terminating MSC120 bytes Information on terminating MSC and associated VLR612 bytes Information on the originating switch and HLR126 bytes Inter MSC handoffs Information on the new MSC and associated VLR148 bytes Information on the new MSC and old MSC383 bytes

Signaling load for location updating in GSM Location UpdatingLoad In formation on the current MSC and associated VLR406 bytes In formation on the current VLR and HLR55 bytes In formation on new VLR and old VLR406 bytes In formation on the new VLR and old VLR213 bytes In formation on the old VLR and HLR95 bytes In formation on the new VLR and HLR182 bytes

SS7 Services Touchstar  This kind of service is also known as CLASS  This is a group of switch-controlled services that provide its users with certain call management capabilities  Services provided are Call return, Call forwarding, Repeat dialing, Call block,Call tracing and Caller ID 8 00 services  These services were introduced by Bell System to provide toll-free access to the calling party to the services and database which is offered by the private parties  The costs associated with the processing of calls is paid by the service subscriber  The service is offered under two plans known as the NXX plan and the 8 00 database plan

…  In NXX plan the first six digits of an 8 00 call are used to select the interexchange carrier (IXC)  In the 8 00 data database plan, the call is looked up in a database to determine the appropriate carrier and routing information Alternating Billing Services And Line Information Database (ADB/LIDB)  These services use the CCS network to enable the calling party to bill a call to a personal number (third party number, calling card, or collect etc.) from any number

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