PSTN Emulation Services

The term "PSTN Emulation" refers to the ability of an IMS network to deliver an exact implementation of local telephony over POTS, precisely matching the functions offered by legacy Class 5 switches down to the last detail.

A complete set of generic local calling features is essential for PSTN Emulation, but there’s a lot more required to satisfy all the needs of local POTS subscribers and fully enable the replacement of legacy Class 5 switches.

For example, there are special local features that are specific to POTS lines, like Single Party Revertive Ringing (sometimes known as "barn phone") and Off-Premises Extension (OPX). Then there are POTS-specific signaling functions such as pulse dialing and Line-Side Answer Supervision. There are network-based services that rely on SS7 / C7 signaling, including Calling Name Delivery, Automatic Callback and Automatic Recall, as well as special applications such as Telemarketer Call Screening that use Advanced Intelligent Network (AIN) technology. Additionally, in the US, local service must typically meet the requirements of Equal Access, where subscribers can not only designate a Preferred Inter-exchange Carrier, but can override this choice on any call by dialing the appropriate prefix. And finally, operator services such as Busy Line Verification need to be supported.

In the IMS architecture, this functionality is implemented by a PSTN Emulation Application Server working in conjunction with an Access Gateway Control Function. MetaSphere supports both of these functions comprehensively, addressing all of the requirements identified above - enabling local service providers to migrate their TDM networks to VoIP and IMS in complete confidence.