Common Channel Signalling System No. 7 (SS7)
Common Channel Signalling System No. 7 (SS7) MSc in Software Development Telecommunications Elective © Dr. Dirk H Pesch, Electronics Dept., CIT, 2000 1 Introduction • Common Channel Signalling System No. 7 (SS7) is data communications network standard • SS7 is intended to be used as a control and management network for telecommunication networks • SS7 provides call management, data base query, routing, flow and congestion control functionality for telecommunication networks • SS7 is specifically designed to support the functions of an Integrated Services Digital Network © Dr. Dirk H Pesch, Electronics Dept., CIT, 2000 2 Hierarchy of Telephone Networks Inter-carrier Exchange (ICX) ICX Tandem Exchange (TdX) Transit Exchange (TX) Local Exchange (LE) TdX TX TX LE LE LE LE © Dr. Dirk H Pesch, Electronics Dept., CIT, 2000 3 Signalling Transmission • DC Signalling – On-Off type digital signals • Tone Signalling – In-band or out-of-band signalling • Digital Control Signals – similar to on-off signals but represent bit sequences • Common Channel Signalling – digital signalling scheme between switches in the network © Dr. Dirk H Pesch, Electronics Dept., CIT, 2000 4 In -band and Out -of -band Signalling Voice channel In-band Out-of-band Output Voltage or Energy 0.3 1 2 3 4 5 Frequency in kHz © Dr. Dirk H Pesch, Electronics Dept., CIT, 2000 5 Common Channel Signalling Non-associated signalling Associated signalling Speech Signalling Switching points Signalling transfer points As public network become more complex and provide a richer set of services, the drawbacks of in-channel signalling become more apparent. The information transfer rate is quite limited and with inband signalling only available if there are no voice signals on the circuit.
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